A magnetic recording apparatus, a multi-state disk, and a read / write method

Abstract

The application discloses a magnetic recording device, a multi-state disk and a read-write method, and belongs to the field of magnetic storage. The magnetic recording device comprises a substrate and a magnetic recording film above the substrate. The magnetic recording film is circular and comprises three ferromagnetic layers separated by two non-magnetic intermediate layers. The easy magnetization directions of the three ferromagnetic layers are along the x, y and z directions respectively. The z direction is the vertical direction, and the x and y directions are in-plane directions and are along the radial direction and the tangential direction respectively. The multi-state disk comprises the magnetic recording device, a read head, a write head and magnetic shielding layers on both sides of the read head. The write head comprises a vertical magnetic pole and two pairs of horizontal magnetic poles, and coils wound on the magnetic poles. The read head comprises a spin current generation layer and a film layer structure (a magnetic tunnel junction, a spin valve or a Hall bar). The application can improve the storage density of the magnetic recording device, thereby greatly improving the storage density of the disk based on the magnetic recording device.

Description

Technical Field

[0001] This invention belongs to the field of magnetic storage, and more specifically, relates to a magnetic recording device, a multi-state disk, and a read / write method. Background Technology

[0002] Magnetic storage devices, such as hard disk drives, are important tools for expanding the data storage capacity of computers. With the rapid increase in the amount of data processed by computers, there is a need to increase the storage density of magnetic recording media to improve computer functionality and capabilities.

[0003] Existing disk storage devices mostly use single-layer magnetic recording media with perpendicular (or in-plane) magnetic anisotropy because the spatial resolution of the read head is insufficient and it can only be used to detect magnetic fields in a single direction. This magnetic recording medium has only two steady states with the magnetization direction vertically upward (horizontally to the left) or vertically downward (horizontally to the right), which means that a single storage cell of the disk storage device can only store one binary piece of information, resulting in low storage density and failing to meet the ever-increasing demand for data storage.

[0004] To achieve higher recording density in magnetic recording media, current methods involve narrowing the width and spacing of write tracks, thereby reducing the number of corresponding magnetic recording bits encoded in each track. Mainstream methods for increasing magnetic recording density include shingled magnetic recording (SMR), heat-assisted magnetic recording (HAMR), microwave-assisted magnetic recording (MAMR), and acoustic-assisted magnetic recording (AAMR). However, reducing the number of magnetic recording bits lowers the energy barrier of the magnetic grains, thus shortening the retention time of the recording bits and affecting the stability and lifespan of the disk. Furthermore, reducing the number of recording bits requires write heads with higher writing accuracy and lower inter-track crosstalk, as well as read heads with higher spatial resolution and stronger noise immunity. These issues significantly limit further increases in disk storage density and capacity.

[0005] In summary, how to improve disk storage density and expand disk storage capacity remains an urgent problem to be solved. Summary of the Invention

[0006] In view of the shortcomings of the prior art and the need for improvement, the present invention provides a magnetic recording device, a multi-state disk and a read / write method, the purpose of which is to improve the storage density of the magnetic recording device, thereby significantly improving the storage density of the disk based on the magnetic recording device.

[0007] To achieve the above objectives, according to one aspect of the present invention, a magnetic recording device is provided, comprising: a substrate, and a magnetic recording thin film thereon;

[0008] The magnetic recording thin film is circular and includes: a first ferromagnetic layer, a first intermediate layer, a second ferromagnetic layer, a second intermediate layer and a third ferromagnetic layer stacked sequentially;

[0009] The easy magnetization directions of the three ferromagnetic layers are along the x, y, and z directions, respectively; the z direction is perpendicular to the surface of the magnetic recording film, the x direction is parallel to the surface of the magnetic recording film and radial, and the y direction is parallel to the surface of the magnetic recording film and tangential.

[0010] Both the first and second intermediate layers are made of non-magnetic materials.

[0011] Furthermore, a soft magnetic layer is also included between the substrate and the magnetic recording thin film.

[0012] According to another aspect of the present invention, a multi-state disk comprising the magnetic recording device described above provided by the present invention is provided, further comprising: a read head, a write head, and magnetic shielding layers located on both sides of the read head;

[0013] The read head includes a spin flow generation layer and a film structure. The spin flow generation layer is cross-shaped and has two mutually perpendicular conductive channels along the x and y directions, respectively. The film structure is a magnetic tunnel junction, a spin valve, or a Hall bar. Each film in the read head is parallel to the magnetic recording film, and the film structure faces the magnetic recording film.

[0014] The writing head includes: a vertical magnetic pole, two first horizontal magnetic poles, two second horizontal magnetic poles, and coils wound around each magnetic pole; the four horizontal magnetic poles are evenly distributed on a circle centered on the vertical magnetic pole, and the line connecting the two second horizontal magnetic poles is perpendicular to the line connecting the two first horizontal magnetic poles.

[0015] The line connecting the two first horizontal magnetic poles is along the x-direction, or the line connecting the two first horizontal magnetic poles has a 45° angle with the x-direction; when the multi-state disk rotates, the read head and write head move relative to the disk surface along the y-direction.

[0016] According to another aspect of the present invention, a method for reading and writing the above-mentioned multi-state disk is provided, comprising: a writing phase; the writing phase comprising:

[0017] Preprocessing steps: Based on the mapping relationship between stored information and magnetization direction, determine the magnetization directions of ferromagnetic layer x, ferromagnetic layer y, and ferromagnetic layer z after the information to be written is written, and denoted as the first magnetization direction, the second magnetization direction, and the third magnetization direction, respectively; ferromagnetic layer x, ferromagnetic layer y, and ferromagnetic layer z are the ferromagnetic layers in the magnetic recording film whose easy magnetization directions are along the x, y, and z directions, respectively;

[0018] z-direction writing step: Apply current to the coil wound on the vertical magnetic pole to generate a writing magnetic field in the z direction, so that the magnetization direction of the ferromagnetic layer z is the third magnetization direction;

[0019] When the line connecting the two first horizontal magnetic poles is along the x-direction, the writing phase also includes:

[0020] The x-direction writing step is as follows: A first current is applied to a pair of coils wound around two second horizontal magnetic poles to generate an auxiliary magnetic field in the y direction. Then, a second current is applied to a pair of coils wound around two first horizontal magnetic poles to generate a writing magnetic field in the x direction. At the same time, the first current is removed to remove the auxiliary magnetic field in the y direction, so that the magnetization direction of the ferromagnetic layer x is the first magnetization direction. The auxiliary magnetic field in the y direction is smaller than the flip field of the ferromagnetic layer y.

[0021] The writing steps in the y direction are as follows: A third current is applied to a pair of coils wound around two first horizontal magnetic poles to generate an auxiliary magnetic field in the x direction. Then, a fourth current is applied to a pair of coils wound around two second horizontal magnetic poles to generate a writing magnetic field in the y direction. At the same time, the third current is removed to remove the auxiliary magnetic field in the x direction, so that the magnetization direction of the ferromagnetic layer y is the second magnetization direction. The auxiliary magnetic field in the x direction is smaller than the flip field of the ferromagnetic layer x.

[0022] When the line connecting the two first horizontal magnetic poles forms a 45° angle with the x-direction, the writing phase also includes:

[0023] Planar writing steps: The two horizontal magnetic poles connected along the combined direction of the first magnetization direction and the second magnetization direction are designated as target horizontal magnetic poles. Current is applied to a pair of coils wound around the two target horizontal magnetic poles to generate a writing magnetic field along the combined direction, so that the magnetization direction of ferromagnetic layer x is the first magnetization direction and the magnetization direction of ferromagnetic layer y is the second magnetization direction.

[0024] The read / write method provided by this invention further includes: a read-out stage; the read-out stage includes the following steps:

[0025] (S1) Calculate the probability P that the free layer magnetization direction is upward when an excitation current is applied in the positive x-axis direction. up (+J x The probability P that the free layer magnetization direction is upward when an excitation current is applied in the negative x-axis direction. up (-J x The probability P that the free layer magnetization direction is upward when an excitation current is applied in the positive y-axis direction. up (+J y And the probability P that the free layer magnetization direction is upward when an excitation current is applied in the negative y-axis direction. up (-J y );

[0026] The free layer is the free layer in the magnetic tunnel junction of the read head;

[0027] (S2) Calculate the x-direction component H of the leakage magnetic field. x y-direction component H y and z-direction component H z The probability P up (Hx ), P up (H y ) and P up (H z The calculation formula is as follows:

[0028]

[0029]

[0030]

[0031] (S3) Based on the pre-calibrated correspondence between the components of the leakage magnetic field in each direction and the probability, determine the x-direction component H of the leakage magnetic field. x y-direction component H y and z-direction component H z The magnetization direction of the corresponding ferromagnetic layer is determined based on the direction of each component of the leakage magnetic field.

[0032] In step (S1), for any direction, the probability of the free layer magnetization direction phase when an excitation current is applied in that direction is statistically analyzed, including:

[0033] (S11) If the film structure is a magnetic tunnel junction or a spin valve, then an excitation current in that direction is applied to the read head through the conductive channel of the spin current generation layer, and after applying a read voltage to the read head, the current at both ends of the read head along the z direction is measured to determine the magnetization direction of the free layer in the magnetic tunnel junction of the read head.

[0034] If the film structure is a Hall bar, an excitation current in that direction is applied to the read head through the conductive channel of the spin current generation layer. After applying a read current to one of the conductive channels, the voltage across the other conductive channel is measured to determine the magnetization direction of the free layer in the magnetic tunnel junction of the read head.

[0035] (S12) Execute step (S11) multiple times to obtain the probability that the magnetization direction of the free layer is upward when the excitation current in this direction is applied.

[0036] According to another aspect of the invention, another magnetic recording device is provided, comprising: a substrate, and a magnetic recording thin film thereon;

[0037] The magnetic recording thin film is circular and includes: a first ferromagnetic layer, a first intermediate layer and a second ferromagnetic layer stacked sequentially;

[0038] The easy magnetization directions of the two ferromagnetic layers are along the planar direction and the perpendicular direction, respectively;

[0039] The first intermediate layer is made of a non-magnetic material.

[0040] Furthermore, a soft magnetic layer is also included between the substrate and the magnetic recording thin film.

[0041] According to another aspect of the present invention, a multi-state disk comprising the above-described magnetic recording device is provided, further comprising: a read head, a write head, and magnetic shielding layers located on both sides of the read head;

[0042] The read head includes a spin flow generation layer and a film structure; the spin flow generation layer is cross-shaped and has two mutually perpendicular conductive channels, one of which is along the y-direction; the film structure is a magnetic tunnel junction, a spin valve, or a Hall bar; each film in the read head is parallel to the magnetic recording film, and the film structure faces the magnetic recording film.

[0043] The write head includes: a vertical magnetic pole, two first horizontal magnetic poles symmetrically arranged about the vertical magnetic pole, and coils wound around each magnetic pole; the line connecting the two first horizontal magnetic poles is along the y-direction; when the multi-state disk rotates, the read head and the write head move relative to the disk surface along the y-direction;

[0044] The y-direction is parallel to the surface of the magnetic recording film and along the tangential direction.

[0045] According to another aspect of the present invention, a method for reading and writing the above-mentioned multi-state disk is provided, comprising: a writing phase; the writing phase comprising:

[0046] Preprocessing steps: Based on the mapping relationship between stored information and magnetization direction, determine the magnetization directions of ferromagnetic layer p and ferromagnetic layer z after the information to be written is written, and denoted as the first magnetization direction and the second magnetization direction, respectively; ferromagnetic layer p and ferromagnetic layer z are the ferromagnetic layers in the magnetic recording film whose easy magnetization direction is along the planar direction and perpendicular direction, respectively.

[0047] Y-direction writing step: Apply current to a pair of coils wound around two first horizontal magnetic poles to generate a writing magnetic field in the y direction, so that the magnetization direction of the ferromagnetic layer p is the first magnetization direction;

[0048] z-direction writing step: Apply current to the coil wound on the vertical magnetic pole to generate a writing magnetic field in the z direction, so that the magnetization direction of the ferromagnetic layer z is the second magnetization direction;

[0049] The z-direction is perpendicular to the surface of the magnetic recording film.

[0050] The read / write method provided by this invention further includes: a read-out stage; the read-out stage includes:

[0051] (T1) Calculate the probability P that the free layer magnetization direction is upward when an excitation current is applied in the positive y-axis direction. up (+J y And the probability P that the free layer magnetization direction is upward when an excitation current is applied in the negative y-axis direction. up(-J y );

[0052] The free layer is the free layer in the magnetic tunnel junction of the read head;

[0053] (T2) Calculate the y-direction component H of the leakage magnetic field. y and z-direction component H z The probability P up (H y ) and P up (H z The calculation formula is as follows:

[0054]

[0055]

[0056] (T3) Based on the pre-calibrated correspondence between the components of the leakage magnetic field in each direction and the probability, determine the y-direction component H of the leakage magnetic field. y and z-direction component H z The magnetization direction of the corresponding ferromagnetic layer is determined based on the direction of each component of the leakage magnetic field.

[0057] In step (T1), for any direction, the probability of the free layer magnetization direction phase when an excitation current is applied in that direction is statistically analyzed, including:

[0058] (T11) If the film structure is a magnetic tunnel junction or a spin valve, then an excitation current in that direction is applied to the read head through the conductive channel of the spin current generation layer, and after applying a read voltage to the read head, the current at both ends of the read head along the z direction is measured to determine the magnetization direction of the free layer in the magnetic tunnel junction of the read head.

[0059] If the film structure is a Hall bar, an excitation current in that direction is applied to the read head through the conductive channel of the spin current generation layer. After applying a read current to one of the conductive channels, the voltage across the other conductive channel is measured to determine the magnetization direction of the free layer in the magnetic tunnel junction of the read head.

[0060] (T12) Execute step (T11) multiple times to obtain the probability that the magnetization direction of the free layer is upward when the excitation current in this direction is applied.

[0061] In summary, the above-described technical solutions conceived in this invention can achieve the following beneficial effects:

[0062] (1) The magnetic recording device provided by the present invention has multiple (two or three) ferromagnetic layers with different magnetization directions. Each ferromagnetic layer can store a binary information. Different magnetization directions in the ferromagnetic layer correspond to different values ​​of the binary information. Therefore, the magnetic recording device provided by the present invention has multiple magnetic recording media. Compared with the traditional single-layer magnetic recording media, the magnetic recording device in the present invention can store more information and greatly improve the storage density of the disk based on the magnetic recording device.

[0063] This invention increases storage density by improving the structure of the magnetic recording device without affecting the magnetic recording bit width. Therefore, it does not affect the stability and lifespan of the disk. Compared with existing methods for increasing magnetic recording density, it also reduces the performance requirements of the read and write heads.

[0064] (2) In the preferred embodiment of the magnetic recording device provided by the present invention, a soft magnetic layer is further provided between the substrate and the magnetic recording film. Due to its low coercivity and high permeability, the soft magnetic layer can effectively reduce the magnitude of the writing magnetic field for the ferromagnetic layer z in the magnetic recording film, thereby effectively reducing power consumption while ensuring accurate information storage.

[0065] (3) The present invention provides a multi-state disk with a three-layer magnetic recording medium, wherein the write head is composed of a vertical magnetic pole and two pairs of horizontal magnetic poles uniformly arranged around the vertical magnetic pole, and each magnetic pole is wound with a coil; there are two arrangement schemes for the horizontal magnetic poles:

[0066] Option 1: The lines connecting the two pairs of horizontal magnetic poles are along the x and y directions, respectively. In this case, by applying current to the coils on the pair of horizontal magnetic poles in the x / y directions, a writing magnetic field in the horizontal x / y directions can be generated accordingly, which is used to change the magnetization direction of the ferromagnetic layer x / ferromagnetic layer y.

[0067] Option 2: Compared to Option 1, the magnetic pole position is rotated 45° around the z-axis; at this time, by passing current through a specific coil, a plane writing magnetic field tilted at 45° can be generated, and the magnetization direction of the ferromagnetic layer along the x and y directions is completed at the same time.

[0068] In both of the above horizontal magnetic pole arrangement schemes, a writing magnetic field in the z-direction can be generated by applying current to the coil wound on the vertical magnetic pole, which can be used to change the magnetization direction of the ferromagnetic layer along the z-direction of easy magnetization.

[0069] Based on this writing head, the present invention can accurately write to the three ferromagnetic layers in the magnetic recording film.

[0070] (4) The present invention provides a multi-state disk with two layers of magnetic recording medium. Its write head is composed of a vertical magnetic pole and a pair of horizontal magnetic poles symmetrically arranged around the vertical magnetic pole. A coil is wound on each magnetic pole. The line connecting the two horizontal magnetic poles is along the y direction. By applying current to the pair of coils on the horizontal magnetic poles, a write magnetic field in the y direction can be generated to change the magnetization direction of the ferromagnetic layer in the y direction. Applying current to the coils wound on the vertical magnetic poles generates a write magnetic field in the z direction to change the magnetization direction of the ferromagnetic layer whose easy magnetization direction is along the z direction. Based on this write head, the present invention can accurately write to the two ferromagnetic layers in the magnetic recording film respectively.

[0071] (5) The multi-state disk with multi-layer (two-layer / three-layer) magnetic recording medium provided by the present invention has a read head that specifically includes a spin flow generation layer and a magnetic tunnel junction. The spin flow generation layer is cross-shaped and has two mutually perpendicular conductive channels. Through the read head with this special structure, the magnetization direction of the corresponding ferromagnetic layer in the magnetic recording film can be accurately determined, thereby completing the reading operation.

[0072] (6) The read / write method for a multi-state disk with a three-layer magnetic recording medium provided by the present invention has two schemes for writing ferromagnetic layer x / ferromagnetic layer y, corresponding to the write head in the disk:

[0073] Option 1: First, apply current to the coil on the other pair of horizontal magnetic poles to generate a small auxiliary magnetic field. This auxiliary magnetic field can deflect the magnetization direction in the ferromagnetic layer to be written. Then, apply current to the coil on the corresponding pair of horizontal magnetic poles of the ferromagnetic layer to be written, so that the magnetization direction changes to the specified direction. This writing method can effectively reduce the size of the writing magnetic field, thereby reducing power consumption. At the same time, it can reduce the probability of accidentally writing to ferromagnetic layer y when writing to ferromagnetic layer x, and the probability of accidentally writing to ferromagnetic layer x when writing to ferromagnetic layer y, thus effectively improving writing accuracy.

[0074] Option 2: Based on the magnetization directions of ferromagnetic layer x and ferromagnetic layer y after writing, determine the direction of the corresponding horizontal writing magnetic field, and apply current to the corresponding coil to generate the corresponding horizontal writing magnetic field, thereby completing the writing of ferromagnetic layer x and ferromagnetic layer y at the same time, reducing the magnitude of the writing magnetic field and accelerating the writing speed.

[0075] (7) The reading and writing method of the multi-state disk with multi-layer (two-layer / three-layer) magnetic recording medium provided by the present invention obtains the probability of the magnetization direction of the free layer in the read head being upward when the excitation current in different directions is applied through statistical means when reading the information stored in the storage unit. This is used as the basis for judging the directional components of the leakage magnetic field. In this way, the magnetization direction of each ferromagnetic layer can be accurately determined, and the reading of the information stored in each ferromagnetic layer can be accurately completed. Attached Figure Description

[0076] Figure 1 This is a schematic diagram of a magnetic recording device provided in an embodiment of the present invention;

[0077] Figure 2 This is a vertical cross-sectional view of the structure of a multi-state disk provided in an embodiment of the present invention;

[0078] Figure 3 This is a top view of the structure of a multi-state disk provided in an embodiment of the present invention;

[0079] Figure 4 This is a schematic diagram of a read head in a multi-state disk according to an embodiment of the present invention;

[0080] Figure 5 This invention provides another schematic diagram of a read head in a multi-state disk;

[0081] Figure 6 This invention provides another schematic diagram of a read head in a multi-state disk;

[0082] Figure 7 A top view of the structure of a multi-state disk provided in another embodiment of the present invention;

[0083] Figure 8 A schematic diagram of a magnetic recording device provided for another embodiment of the present invention. Detailed Implementation

[0084] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0085] In this invention, the terms "first," "second," etc. (if present) in the invention and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0086] Before explaining the technical solution of this embodiment in detail, the principle of information storage by magnetic recording media in a disk is briefly introduced as follows:

[0087] For a single-layer magnetic recording medium, there are two stable magnetization directions, each corresponding to a different value of binary information. For example, for a magnetic recording medium with an easily magnetized direction perpendicular to the magnetic field, there are two stable states: vertically upward or vertically downward. In actual storage, these two stable states can be used to represent the two values ​​of binary information. Current hard disks only use a single-layer magnetic recording medium; therefore, a single storage unit can only store one binary piece of information.

[0088] To address the low storage density of existing single-layer magnetic recording media disks, this invention provides a magnetic recording device, a multi-mode disk, and a read / write method. The overall concept is to improve the structure of the magnetic recording device so that it has multiple layers of recording media that can be used to store information, effectively improving the unit's information storage capacity and increasing the disk's storage density.

[0089] The following is an example.

[0090] Example 1:

[0091] A magnetic recording device, such as Figure 1 As shown, it includes: a substrate, and a magnetic recording thin film on the substrate;

[0092] The magnetic recording thin film is circular and includes: a first ferromagnetic layer, a first intermediate layer, a second ferromagnetic layer, a second intermediate layer and a third ferromagnetic layer stacked sequentially;

[0093] The easy magnetization directions of the three ferromagnetic layers are along the x, y, and z directions, respectively; the z direction is perpendicular to the surface of the magnetic recording film, the x direction is parallel to the surface of the magnetic recording film and radial, and the y direction is parallel to the surface of the magnetic recording film and tangential.

[0094] Both the first and second intermediate layers are made of non-magnetic materials.

[0095] For ease of description, in the following embodiments, the ferromagnetic layers with easy magnetization directions along the x, y, and z directions are respectively denoted as ferromagnetic layer x, ferromagnetic layer y, and ferromagnetic layer z; as shown Figure 1 As shown in this embodiment, ferromagnetic layer x, ferromagnetic layer y, and ferromagnetic layer z are arranged sequentially from top to bottom. It should be noted that the specific order of the three ferromagnetic layers is not explicitly limited in this invention; it is only necessary to ensure that there is an intermediate layer between two adjacent ferromagnetic layers.

[0096] The intermediate layer is used to ensure low interlayer exchange coupling between adjacent ferromagnetic layers, namely between ferromagnetic layer z and ferromagnetic layer y, and between ferromagnetic layer y and ferromagnetic layer x, thereby reducing mutual interference between ferromagnetic layers. It is easy to understand that the thickness of the intermediate layer should be set appropriately by taking into account both the interlayer exchange coupling and the attenuation of the writing magnetic field. If the thickness is set too low, low interlayer exchange coupling cannot be guaranteed. If it is set too high, the attenuation of the writing magnetic field may be too great.

[0097] In this embodiment, since the easy magnetization directions of the three ferromagnetic layers are different, by applying a magnetic field along the x, y, or z direction, the easy magnetization axis can be reversed along the corresponding direction of the magnetization direction of the ferromagnetic layer (x, y, z) without affecting the magnetization direction of the other ferromagnetic layers.

[0098] In this embodiment, each of the three ferromagnetic layers can store one binary information. Different magnetization directions within the ferromagnetic layers correspond to different values ​​of the binary information. Specifically, ferromagnetic layer z has two states along the magnetization direction: +z and -z; ferromagnetic layer y has two states along the magnetization direction: +y and -y; and ferromagnetic layer x has two states along the magnetization direction: +x and -x. This gives the magnetic recording film a total of eight magnetic recording states, which can record one octal bit or three binary bits of information. Compared to traditional single-layer magnetic recording devices, this effectively improves the storage density of the storage unit.

[0099] like Figure 1 As shown, in this embodiment, a soft magnetic layer is further included between the substrate and the magnetic recording thin film; the soft magnetic layer can effectively reduce the magnitude of the writing magnetic field for the ferromagnetic layer z, thereby effectively reducing power consumption while ensuring accurate information storage.

[0100] In this embodiment, the ferromagnetic layer may be selected from: Co alloys, including CoFeB, CoCrTa, CoCrPt, CoCrPtTa, CoNiCrPt, etc.; L10 alloys, including FePt, FePd, CoPt, MnAl, etc.; rare earth transition metals, including Fe 14 Materials such as Nd₂B and SmCo₅ can be used. The intermediate layer can be a non-magnetic oxide, including MgO and Al₂O₃. The soft magnetic layer can be a high-permeability NiFe alloy.

[0101] In this embodiment, ferromagnetic layers x and y can be obtained by substrate texturing, anisotropic etching, directional deposition, sputtering or annealing with an external magnetic field, and adding a Cr or Cr alloy (CrV, CrTi, CrMo) substrate. Ferromagnetic layer z can be obtained through interface effects, etc.; ferromagnetic layer z can also be obtained by utilizing the properties of the material itself. For example, CoCr alloys and rare earth transition metals have perpendicularity. By using these materials to prepare ferromagnetic layer z, a ferromagnetic layer with the easy magnetization direction along the z-direction can be obtained.

[0102] Example 2:

[0103] A multi-state disk comprising the magnetic recording device provided in Embodiment 1 above, such as Figure 2 and Figure 3 As shown, the multi-state disk also includes: a read head, a write head, and magnetic shielding layers located on both sides of the read head.

[0104] like Figure 2 and Figure 3As shown, the writing head includes: a vertical magnetic pole, two first horizontal magnetic poles, two second horizontal magnetic poles, and coils wound around each magnetic pole; the four horizontal magnetic poles are evenly distributed on a circle centered on the vertical magnetic pole, and the line connecting the two second horizontal magnetic poles is perpendicular to the line connecting the two first horizontal magnetic poles; the line connecting the two first horizontal magnetic poles is along the x-direction, and correspondingly, the line connecting the two second horizontal magnetic poles is along the y-direction.

[0105] The multi-mode disk provided in this embodiment has a magnetic recording device with three layers of magnetic recording media. The write head can generate write magnetic fields in three directions: x, y, and z. Specifically, by applying current to a coil on a pair of horizontal magnetic poles in the x direction, a horizontal write magnetic field in the x direction is generated, which is used to change the magnetization direction of the ferromagnetic layer x; by applying current to a coil on a pair of horizontal magnetic poles in the y direction, a horizontal write magnetic field in the y direction is generated, which is used to change the magnetization direction of the ferromagnetic layer y; and by applying current to a coil wound around a vertical magnetic pole, a write magnetic field in the z direction is generated, which is used to change the magnetization direction of the ferromagnetic layer whose easy magnetization axis is along the z direction. Based on the above write head structure, by applying current to a specific coil, a magnetic field along the x, y, or z direction can be generated, causing the easy magnetization axis to flip along the corresponding direction of the ferromagnetic layer's magnetization direction without affecting the magnetization direction of other ferromagnetic layers, thereby achieving accurate writing.

[0106] like Figure 4 As shown, the read head includes a spin current generation layer and a magnetic tunnel junction. The spin current generation layer is cross-shaped and has two mutually perpendicular conductive channels along the x and y directions, respectively, for conducting current and converting excitation current into spin current. The magnetic tunnel junction includes a free layer, a tunneling layer, and a fixed layer in sequence. The free layer is a nanomagnetic material with perpendicular magnetic anisotropy, serving as a nanomagnet for sensing the magnetic field. Each film layer in the read head is parallel to the magnetic recording film, and the magnetic tunnel junction faces the magnetic recording film.

[0107] The spin flow generating layer can be made of heavy metal materials such as Ta, Pt, W, Mo, Pd, Nb, etc., or topological insulator materials such as Bi₂Se₃, α-Sn, Sb₂Te₃, Bi₂Te₃, Bi₂Se₃, etc. x Sb 2-x Te3, Bi2Te2Se, etc. Free and fixed layers can be made of CoFeB, CoMnSi, CoFeSi, CoFeAl, GaMnAs, CoFeAlSi, CoFe, FePt, CoPt, FeNi, Fe, Co, Ni, etc. Tunneling layers can be made of MgO, Al2O3, AlO x , TiO2, HfO2, MgAlO4, AlN, BN, etc.

[0108] In a read head, the magnetization direction of the fixed layer is fixed. By passing an excitation current through the conductive channel of the read head and then applying a read voltage in the z-direction, the relationship between the magnetization direction of the free layer and the magnetization direction of the fixed layer can be determined, thus determining the magnetization direction of the free layer. The ferromagnetic layers x, y, and z of the magnetic recording thin film generate leakage magnetic fields H with x-, y-, and z-direction components, respectively, at the magnetic read head. x H y H z By measuring the direction of the leakage magnetic field with the read head, the magnetization direction of the corresponding ferromagnetic layer in the magnetic recording thin film can be determined.

[0109] The magnetic shielding layer is used to prevent the leakage magnetic field of the write head and adjacent magnetic recording bits from affecting the read head, thereby affecting the read accuracy. It is easy to understand that the magnetic shielding layer is located between the read and write heads on the side of the read head that is closer to the write head.

[0110] It should be noted that in some other embodiments of the present invention, the magnetic tunnel junction in the read head can also be replaced with a spin valve, such as... Figure 5 As shown, the spin valve sequentially comprises a first magnetic layer, a non-magnetic intermediate layer, a second magnetic layer, and a pinned layer, wherein the first magnetic layer is a free layer. In this read head structure, if the first and second magnetic layers have the same magnetization direction, the spin valve exhibits a low-resistance state, and a larger measured current is obtained; if the first and second magnetic layers have opposite magnetization directions, the spin valve exhibits a high-resistance state, and a smaller measured current is obtained. Therefore, by applying a reading voltage in the z-direction of the read head, the relationship between the magnetization direction of the free layer (first magnetic layer) and the magnetization direction of the fixed layer (second magnetic layer) in the read head can be determined, thereby determining the magnetization direction of the free layer.

[0111] In other embodiments of the present invention, the magnetic tunnel junction in the read head can also be replaced with a Hall bar structure, such as... Figure 6 As shown, the Hall bar structure consists of a magnetic material layer and an oxide layer, with the magnetic material layer being a free layer. In this read head structure, a read current is passed into the x-direction (or y-direction) of the spin current generation layer, and the voltage in the y-direction (or x-direction) of the spin current generation layer is measured. The magnetization direction of the free layer (magnetic material layer) can then be determined based on the voltage level.

[0112] Example 3:

[0113] The read / write method for the polymorphic disk provided in Embodiment 2 above includes a write phase and a read phase.

[0114] The writing stage involves applying a writing magnetic field to change the magnetization direction of each ferromagnetic layer in the magnetic recording film to a specified direction, thus completing the writing process. In this embodiment, the writing stage specifically includes:

[0115] Preprocessing steps: Based on the mapping relationship between stored information and magnetization direction, determine the magnetization directions of ferromagnetic layer x, ferromagnetic layer y, and ferromagnetic layer z after the information to be written is written, and denoted as the first magnetization direction, the second magnetization direction, and the third magnetization direction, respectively; ferromagnetic layer x, ferromagnetic layer y, and ferromagnetic layer z are the ferromagnetic layers in the magnetic recording film whose easy magnetization directions are along the x, y, and z directions, respectively;

[0116] z-direction writing step: Apply current to the coil wound on the vertical magnetic pole to generate a writing magnetic field in the z direction, so that the magnetization direction of the ferromagnetic layer z is the third magnetization direction;

[0117] The x-direction writing step involves applying a first current to a pair of coils wound around two second horizontal magnetic poles to generate an auxiliary magnetic field in the y-direction, then applying a second current to a pair of coils wound around two first horizontal magnetic poles to generate a writing magnetic field in the x-direction, and simultaneously removing the first current to remove the auxiliary magnetic field in the y-direction, so that the magnetization direction of the ferromagnetic layer x is the first magnetization direction; the auxiliary magnetic field in the y-direction is smaller than the flip field of the ferromagnetic layer y.

[0118] The y-direction writing step is as follows: A third current is applied to a pair of coils wound around two first horizontal magnetic poles to generate an auxiliary magnetic field in the x-direction. Then, a fourth current is applied to a pair of coils wound around two second horizontal magnetic poles to generate a writing magnetic field in the y-direction. At the same time, the third current is removed to remove the auxiliary magnetic field in the x-direction, so that the magnetization direction of the ferromagnetic layer y is the second magnetization direction. The auxiliary magnetic field in the x-direction is smaller than the flip field of the ferromagnetic layer x.

[0119] In this embodiment, the writing of ferromagnetic layer x and ferromagnetic layer y is performed in two steps by applying a magnetic field. Taking the writing of ferromagnetic layer x as an example, during the writing process, a current is first applied to the coils on a pair of horizontal magnetic poles in the y direction to generate a small auxiliary magnetic field. This auxiliary magnetic field is smaller than the flip field of ferromagnetic layer y, which can cause a certain deflection in the magnetization direction of the ferromagnetic layer to be written (i.e., ferromagnetic layer x) without causing ferromagnetic layer y to flip. Then, a current is applied to the coils on the pair of horizontal magnetic poles corresponding to ferromagnetic layer x to change the magnetization direction to the specified direction. The writing process of ferromagnetic layer y is similar.

[0120] This writing method effectively reduces the size of the writing magnetic field, thereby reducing power consumption. It also reduces the probability of accidentally writing to the ferromagnetic layer y when writing to the ferromagnetic layer x, and the probability of accidentally writing to the ferromagnetic layer x when writing to the ferromagnetic layer y, thus effectively improving writing accuracy.

[0121] In the readout stage, the magnetization direction of each ferromagnetic layer in the magnetic recording thin film is determined, thus completing the readout. In this embodiment, the readout stage specifically includes the following steps:

[0122] (S1) Calculate the probability P that the free layer magnetization direction is upward when an excitation current is applied in the positive x-axis direction. up (+J x The probability P that the free layer magnetization direction is upward when an excitation current is applied in the negative x-axis direction. up (-J x The probability P that the free layer magnetization direction is upward when an excitation current is applied in the positive y-axis direction. up (+J y And the probability P that the free layer magnetization direction is upward when an excitation current is applied in the negative y-axis direction. up (-J y );

[0123] The free layer is the free layer in the magnetic tunnel junction of the read head;

[0124] (S2) Calculate the x-direction component H of the leakage magnetic field. x y-direction component H y and z-direction component H z The probability P up (H x ), P up (H y ) and P up (H z The calculation formula is as follows:

[0125]

[0126]

[0127]

[0128] (S3) Based on the pre-calibrated correspondence between the components of the leakage magnetic field in each direction and the probability, determine the x-direction component H of the leakage magnetic field. x y-direction component H y and z-direction component H z The magnetization direction of the corresponding ferromagnetic layer is determined based on the direction of each component of the leakage magnetic field.

[0129] Taking the positive x-axis as an example, the probability of the free layer magnetization direction being upward when an excitation current is applied in this direction is statistically analyzed, specifically including:

[0130] (S11) An excitation current in the positive x-axis direction is applied to the read head through the x-direction conductive channel of the spin current generation layer, and a read voltage is applied to the read head. The current at both ends of the read head along the z-direction is measured. If the measured current is a large current (greater than a preset threshold), then the magnetization direction of the free layer is opposite to that of the fixed layer; if the measured voltage is a small current (less than a preset threshold), then the magnetization direction of the free layer is the same as that of the fixed layer. By combining the magnetization direction of the fixed layer, the magnetization direction of the free layer in the magnetic tunnel junction of the read head can be determined.

[0131] (S12) Execute step (S11) multiple times to obtain the probability P that the free layer magnetization direction is upward when an excitation current is applied in the positive x-axis direction. up (+J x );

[0132] The probability P of the free layer magnetization direction being upward when an excitation current is applied in the negative x-axis direction. up (-J x The probability P that the free layer magnetization direction is upward when an excitation current is applied in the positive y-axis direction. up (+J y And the probability P that the free layer magnetization direction is upward when an excitation current is applied in the negative y-axis direction. up (-J y This can be obtained statistically using a similar method; it is easy to understand that the excitation current in the y-direction is applied through the conductive channel in the y-direction of the spin current generation layer.

[0133] In this embodiment, when reading the information stored in the storage unit, the probability of the magnetization direction of the free layer in the read head being upward when excitation currents in different directions are applied is obtained statistically. This is used as the basis for judging the directional components of the leakage magnetic field. In this way, the magnetization direction of each ferromagnetic layer can be accurately determined, and the information stored in each ferromagnetic layer can be accurately read.

[0134] It should be noted that the steps in step (S11) differ slightly depending on the read head structure. Taking the positive x-axis direction as an example, when the read head uses a spin valve structure, the execution process of step (S11) is as follows: An excitation current in the positive x-axis direction is applied to the read head through the x-direction conductive channel of the spin current generation layer. After applying a read voltage to the read head, the current at both ends of the read head along the z-direction is measured. If the measured current is large (greater than a preset threshold), then the magnetization direction of the free layer (first magnetic layer) is opposite to the magnetization direction of the fixed layer (second free layer). If the measured voltage is small (less than a preset threshold), then the magnetization direction of the free layer is the same as the magnetization direction of the fixed layer. Combining the magnetization direction of the fixed layer, the magnetization direction of the free layer in the magnetic tunnel junction of the read head can be determined.

[0135] When the read head uses a Hall bar structure, the execution process of step (S11) is as follows:

[0136] An excitation current in the positive x-axis direction is applied to the read head through the conductive channel of the spin current generation layer. After applying a read current to one of the conductive channels, the voltage across the other conductive channel is measured. The voltage level is related to the direction and magnitude of the magnetization intensity of the magnetic material layer. Therefore, the magnetization direction of the free layer (magnetic material layer) can be determined by the voltage level.

[0137] Example 4:

[0138] A multi-state disk comprising the magnetic recording device provided in Embodiment 1 above, the difference between this embodiment and Embodiment 2 above lies in the arrangement of the horizontal magnetic poles in the write head. For example... Figure 7 As shown, in this embodiment, the line connecting the two first horizontal magnetic poles has a 45° angle with the x-direction, which is equivalent to rotating the horizontal magnetic poles counterclockwise by 45° based on the above embodiment 2.

[0139] By arranging the horizontal magnetic poles in this way, a planar writing magnetic field tilted at 45° can be generated. The four horizontal magnetic poles can generate writing magnetic fields in four directions: when the writing magnetic field direction is rotated 45° counterclockwise along the positive x-axis, it can simultaneously write the +x direction of ferromagnetic layer x and the +y direction of ferromagnetic layer y; when the writing magnetic field direction is rotated 45° clockwise along the positive x-axis, it can simultaneously write the +x direction of ferromagnetic layer x and the -y direction of ferromagnetic layer y; when the writing magnetic field direction is rotated 135° counterclockwise along the positive x-axis, it can simultaneously write the -x direction of ferromagnetic layer x and the +y direction of ferromagnetic layer y; when the writing magnetic field direction is rotated 135° clockwise along the positive x-axis, it can simultaneously write the -x direction of ferromagnetic layer x and the -y direction of ferromagnetic layer y.

[0140] like Figure 7 As shown, the four horizontal magnetic poles are designated as horizontal pole 1, horizontal pole 2, horizontal pole 3, and horizontal pole 4. Horizontal poles 1 and 2 are used to simultaneously write to the +x and +y directions of ferromagnetic layer x and ferromagnetic layer y, and simultaneously write to the -x and -y directions of ferromagnetic layer x and ferromagnetic layer y. Horizontal poles 3 and 4 are used to simultaneously write to the +x and -y directions of ferromagnetic layer x and ferromagnetic layer y, and simultaneously write to the -x and +y directions of ferromagnetic layer x and ferromagnetic layer y. The vertical magnetic pole is used to write to the +z and -z directions of ferromagnetic layer z.

[0141] The write head with this structure can generate a specific planar magnetic field, and simultaneously write to the ferromagnetic layer x and the ferromagnetic layer y, thereby reducing the size of the write field and speeding up the write process.

[0142] In this embodiment, the read head is the same as in Embodiment 2 above, and its specific implementation can be referred to the description in Embodiment 2 above.

[0143] Example 5:

[0144] The read / write method for the polymorphic disk provided in Embodiment 4 above includes a write phase and a read phase.

[0145] Similarly, during the writing stage, a writing magnetic field is applied to change the magnetization direction of each ferromagnetic layer in the magnetic recording film to a specified direction, thus completing the writing process. In this embodiment, the writing stage specifically includes:

[0146] Preprocessing steps: Based on the mapping relationship between stored information and magnetization direction, determine the magnetization directions of ferromagnetic layer x, ferromagnetic layer y, and ferromagnetic layer z after the information to be written is written, and denoted as the first magnetization direction, the second magnetization direction, and the third magnetization direction, respectively; ferromagnetic layer x, ferromagnetic layer y, and ferromagnetic layer z are the ferromagnetic layers in the magnetic recording film whose easy magnetization directions are along the x, y, and z directions, respectively;

[0147] Planar writing steps: The two horizontal magnetic poles connected along the combined direction of the first magnetization direction and the second magnetization direction are designated as target horizontal magnetic poles. Current is applied to a pair of coils wound around the two target horizontal magnetic poles to generate a writing magnetic field along the combined direction, so that the magnetization direction of ferromagnetic layer x is the first magnetization direction and the magnetization direction of ferromagnetic layer y is the second magnetization direction.

[0148] This writing method allows for the simultaneous writing of ferromagnetic layer x and ferromagnetic layer y, reducing the size of the writing field while accelerating the writing speed.

[0149] Similarly, in the readout stage, the magnetization direction of each ferromagnetic layer in the magnetic recording thin film is determined, thus completing the readout. In this embodiment, the steps of the readout stage are the same as in Embodiment 3 above, and the specific implementation method can be found in the description of Embodiment 3 above.

[0150] Example 6:

[0151] A magnetic recording device, such as Figure 8 As shown, it includes: a substrate, and a magnetic recording thin film on the substrate;

[0152] The magnetic recording thin film is circular and includes: a first ferromagnetic layer, a first intermediate layer and a second ferromagnetic layer stacked sequentially;

[0153] The easy magnetization directions of the two ferromagnetic layers are along the planar direction and the perpendicular direction, respectively;

[0154] The first intermediate layer is made of a non-magnetic material.

[0155] For ease of description, in the following embodiments, the ferromagnetic layers with easy magnetization directions along the planar direction and the perpendicular direction are respectively denoted as ferromagnetic layer p and ferromagnetic layer z. Furthermore, the direction perpendicular to the surface of the magnetic recording film is defined as the z-direction, and the direction parallel to the magnetic recording surface and tangentially is defined as the y-direction; as shown... Figure 8 As shown in this embodiment, the ferromagnetic layer p and the ferromagnetic layer z are arranged sequentially from top to bottom. It should be noted that the specific order of the two ferromagnetic layers is not explicitly limited in this invention. It is only necessary to ensure that there is an intermediate layer between two adjacent ferromagnetic layers.

[0156] The intermediate layer is used to ensure low interlayer exchange coupling between ferromagnetic layer p and ferromagnetic layer z, thereby reducing mutual interference between ferromagnetic layers. It is easy to understand that the thickness of the intermediate layer should be set appropriately by taking into account both the interlayer exchange coupling and the attenuation of the writing magnetic field. If the thickness is set too low, low interlayer exchange coupling cannot be guaranteed. If it is set too thick, the attenuation of the writing magnetic field may be too great.

[0157] In this embodiment, since the easy magnetization directions of the two ferromagnetic layers are different, by applying a magnetic field along the y or z direction, the magnetization directions of the ferromagnetic layers p and z along the corresponding directions can be reversed without affecting the magnetization directions of other ferromagnetic layers.

[0158] In this embodiment, each of the two ferromagnetic layers can store one binary information. Different magnetization directions within the ferromagnetic layers correspond to different values ​​of the binary information. Specifically, the ferromagnetic layer z has two states along the magnetization direction: +z and -z, and the ferromagnetic layer p has two states along the magnetization direction: +y and -y. This gives the magnetic recording film a total of four magnetic recording states, which can record one quaternary bit or two binary bits of information. Compared with traditional single-layer magnetic recording devices, this effectively improves the storage density of the storage unit.

[0159] like Figure 8 As shown, in this embodiment, a soft magnetic layer is further included between the substrate and the magnetic recording film; the soft magnetic layer can effectively reduce the magnitude of the writing magnetic field for the ferromagnetic layer z in the magnetic recording film, thereby effectively reducing power consumption while ensuring accurate information storage.

[0160] In this embodiment, the selection of materials for the ferromagnetic layer, intermediate layer and soft magnetic layer can be referred to the description in Example 1 above, and will not be repeated here.

[0161] In this embodiment, the method of obtaining the ferromagnetic layer p and the ferromagnetic layer z can be referred to the description in Embodiment 1 above, and will not be repeated here.

[0162] Example 7:

[0163] A multi-state disk comprising the magnetic recording device provided in Embodiment 6 above, the multi-state disk further comprising: a read head, a write head, and magnetic shielding layers located on both sides of the read head;

[0164] The writing head includes: a vertical magnetic pole, two first horizontal magnetic poles symmetrically arranged about the vertical magnetic pole, and coils wound around each magnetic pole; the line connecting the two first horizontal magnetic poles is along the y-direction.

[0165] The multi-mode disk provided in this embodiment has a magnetic recording device with two layers of magnetic recording media. The write head can generate write magnetic fields in both the y and z directions. Specifically, by applying current to a coil on a pair of horizontal magnetic poles in the y direction, a corresponding horizontal y-direction write magnetic field is generated to change the magnetization direction of the ferromagnetic layer p. By applying current to a coil wound on a vertical magnetic pole, a z-direction write magnetic field is generated to change the magnetization direction of the ferromagnetic layer whose easy magnetization axis is along the z direction. Based on this write head structure, by applying current to a specific coil, a magnetic field along the y or z direction can be generated, causing the easy magnetization axis to flip along the corresponding direction of the ferromagnetic layer without affecting the magnetization direction of other ferromagnetic layers, thereby achieving accurate writing.

[0166] In this embodiment, the read head is the same as in Embodiment 2 above. For details, please refer to the description of Embodiment 2 above, which will not be repeated here.

[0167] Similarly, in this embodiment, the magnetic shielding layer is used to prevent the leakage magnetic field of the write head and adjacent magnetic recording bits from affecting the read head.

[0168] Example 8:

[0169] The multi-state disk read / write method provided in Embodiment 7 above includes: a write phase and a read phase;

[0170] Similarly, during the writing stage, a writing magnetic field is applied to change the magnetization direction of each ferromagnetic layer in the magnetic recording film to a specified direction, thus completing the writing process. In this embodiment, the writing stage specifically includes:

[0171] Preprocessing steps: Based on the mapping relationship between stored information and magnetization direction, determine the magnetization directions of ferromagnetic layer p and ferromagnetic layer z after the information to be written is written, and denoted as the first magnetization direction and the second magnetization direction, respectively; ferromagnetic layer p and ferromagnetic layer z are the ferromagnetic layers in the magnetic recording film whose easy magnetization direction is along the planar direction and perpendicular direction, respectively.

[0172] Y-direction writing step: Apply current to a pair of coils wound around two first horizontal magnetic poles to generate a writing magnetic field in the y direction, so that the magnetization direction of the ferromagnetic layer p is the first magnetization direction;

[0173] z-direction writing step: Apply current to the coil wound on the vertical magnetic pole to generate a writing magnetic field in the z direction, so that the magnetization direction of the ferromagnetic layer z is the second magnetization direction.

[0174] Similarly, in the readout stage, the magnetization direction of each ferromagnetic layer in the magnetic recording thin film is determined, thus completing the readout. In this embodiment, the readout stage specifically includes the following steps:

[0175] (T1) Calculate the probability P that the free layer magnetization direction is upward when an excitation current is applied in the positive y-axis direction. up (+J y And the probability P that the free layer magnetization direction is upward when an excitation current is applied in the negative y-axis direction. up (-J y );

[0176] The free layer is the free layer in the magnetic tunnel junction of the read head;

[0177] (T2) Calculate the y-direction component H of the leakage magnetic field. y and z-direction component H z The probability P up (H y ) and P up (H z The calculation formula is as follows:

[0178]

[0179]

[0180] (T3) Based on the pre-calibrated correspondence between the components of the leakage magnetic field in each direction and the probability, determine the y-direction component H of the leakage magnetic field. y and z-direction component H z The magnetization direction of the corresponding ferromagnetic layer is determined based on the direction of each component of the leakage magnetic field.

[0181] Taking the positive y-axis direction as an example, the probability of the free layer magnetization direction being upward when an excitation current is applied in this direction is statistically analyzed. Specifically, this includes: (T11) applying an excitation current in the positive y-axis direction to the read head through the y-direction conductive channel of the spin current generation layer, and after applying a read voltage to the read head, measuring the current at both ends of the read head along the z-direction. If the measured current is a large current (greater than a preset threshold), then the magnetization direction of the free layer is opposite to that of the fixed layer; if the measured current is a small current (less than a preset threshold), then the magnetization direction of the free layer is the same as that of the fixed layer. Combining the magnetization direction of the fixed layer, the magnetization direction of the free layer in the magnetic tunnel junction of the read head can be determined.

[0182] (T12) Execute step (T11) multiple times. The probability P of the free layer magnetization direction being upward when the excitation current is in the positive y-axis direction is... up(+J y );

[0183] The probability P of the free layer magnetization direction being upward when an excitation current is applied in the negative y-axis direction. up (-J y This can be obtained through similar statistical methods.

[0184] When reading the information stored in the memory cell, the probability of the magnetization direction of the free layer in the read head being upward when excitation current is applied in different directions is obtained by statistical method. This is used as the basis for judging the directional components of the leakage magnetic field. In this way, the magnetization direction of each ferromagnetic layer can be accurately determined, and the information stored in each ferromagnetic layer can be accurately read.

[0185] Similarly, when the read head structure changes, the execution steps of step (T11) are slightly different. Please refer to the description in Example 3 above for details.

[0186] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A magnetic recording device, characterized in that, include: A substrate, and a magnetic recording thin film thereon; The magnetic recording film is circular and includes: a first ferromagnetic layer, a first intermediate layer, a second ferromagnetic layer, a second intermediate layer and a third ferromagnetic layer stacked sequentially. The easy magnetization directions of the three ferromagnetic layers are along the x, y, and z directions, respectively; the z direction is perpendicular to the surface of the magnetic recording film, the x direction is parallel to the surface of the magnetic recording film and radial, and the y direction is parallel to the surface of the magnetic recording film and tangential; each ferromagnetic layer is used to store one binary information, and different magnetization directions within the ferromagnetic layer correspond to different values ​​of the binary information; Both the first intermediate layer and the second intermediate layer are made of non-magnetic materials.

2. The magnetic recording device as described in claim 1, characterized in that, A soft magnetic layer is also included between the substrate and the magnetic recording thin film.

3. A multi-state magnetic disk comprising the magnetic recording apparatus of claim 1 or 2, characterized in that, Also includes: A read head, a write head, and magnetic shielding layers located on both sides of the read head; The read head includes a spin flow generation layer and a film structure; the spin flow generation layer is cross-shaped and has two mutually perpendicular conductive channels along the x and y directions respectively; the film structure is a magnetic tunnel junction, a spin valve, or a Hall bar; each film layer in the read head is parallel to the magnetic recording film, and the film structure faces the magnetic recording film; The writing head includes: a vertical magnetic pole, two first horizontal magnetic poles, two second horizontal magnetic poles, and a coil wound around each magnetic pole; the four horizontal magnetic poles are evenly distributed on a circumference centered on the vertical magnetic pole, and the line connecting the two second horizontal magnetic poles is perpendicular to the line connecting the two first horizontal magnetic poles. The line connecting the two first horizontal magnetic poles is along the x-direction, or the line connecting the two first horizontal magnetic poles has a 45° angle with the x-direction; when the multi-state disk rotates, the read head and write head move relative to the disk surface along the y-direction.

4. The read / write method for a multi-state disk as described in claim 3, characterized in that, include: Write phase; The writing phase includes: Preprocessing steps: Based on the mapping relationship between stored information and magnetization direction, determine the magnetization directions of ferromagnetic layer x, ferromagnetic layer y, and ferromagnetic layer z after the information to be written is written, and denoted as the first magnetization direction, the second magnetization direction, and the third magnetization direction, respectively; ferromagnetic layer x, ferromagnetic layer y, and ferromagnetic layer z are the ferromagnetic layers in the magnetic recording film whose easy magnetization directions are along the x, y, and z directions, respectively; z-direction writing step: Apply current to the coil wound on the vertical magnetic pole to generate a writing magnetic field in the z direction, so that the magnetization direction of the ferromagnetic layer z is the third magnetization direction; When the line connecting the two first horizontal magnetic poles is along the x-direction, the writing phase further includes: The x-direction writing step involves applying a first current to a pair of coils wound around two second horizontal magnetic poles to generate an auxiliary magnetic field in the y-direction, then applying a second current to a pair of coils wound around two first horizontal magnetic poles to generate a writing magnetic field in the x-direction, and simultaneously removing the first current to remove the auxiliary magnetic field in the y-direction, so that the magnetization direction of the ferromagnetic layer x is the first magnetization direction; the auxiliary magnetic field in the y-direction is smaller than the flip field of the ferromagnetic layer y. The y-direction writing step is as follows: A third current is applied to a pair of coils wound around two first horizontal magnetic poles to generate an auxiliary magnetic field in the x-direction. Then, a fourth current is applied to a pair of coils wound around two second horizontal magnetic poles to generate a writing magnetic field in the y-direction. At the same time, the third current is removed to remove the auxiliary magnetic field in the x-direction, so that the magnetization direction of the ferromagnetic layer y is the second magnetization direction. The auxiliary magnetic field in the x-direction is smaller than the flip field of the ferromagnetic layer x. When the line connecting the two first horizontal magnetic poles forms a 45° angle with the x-direction, the writing stage further includes: Planar writing step: Two horizontal magnetic poles connected along the combined direction of the first magnetization direction and the second magnetization direction are designated as target horizontal magnetic poles. Current is applied to a pair of coils wound around the two target horizontal magnetic poles to generate a writing magnetic field along the combined direction, so that the magnetization direction of ferromagnetic layer x is the first magnetization direction and the magnetization direction of ferromagnetic layer y is the second magnetization direction.

5. The read / write method as described in claim 4, characterized in that, Also includes: Reading stage; The readout stage includes the following steps: (S1) Calculate the probability P that the magnetization direction of the free layer is upward when an excitation current is applied in the positive x-axis direction. up (+J x The probability P that the free layer magnetization direction is upward when an excitation current is applied in the negative x-axis direction. up (-J x The probability P that the free layer magnetization direction is upward when an excitation current is applied in the positive y-axis direction. up (+J y And the probability P that the free layer magnetization direction is upward when an excitation current is applied in the negative y-axis direction. up (-J y ); The free layer is the free layer in the magnetic tunnel junction of the read head; (S2) Calculate the x-direction component H of the leakage magnetic field. x y-direction component H y and z-direction component H z The probability P up (H x ), P up (H y ) and P up (H z The calculation formula is as follows: (S3) Based on the pre-calibrated correspondence between the components of the leakage magnetic field in each direction and the probability, determine the x-direction component H of the leakage magnetic field. x y-direction component H y and z-direction component H z The magnetization direction of the corresponding ferromagnetic layer is determined based on the direction of each component of the leakage magnetic field. In step (S1), for any direction, the probability of the free layer magnetization direction phase when an excitation current is applied in that direction is statistically analyzed, including: (S11) If the film structure is a magnetic tunnel junction or a spin valve, then an excitation current in that direction is applied to the read head through the conductive channel of the spin current generation layer, and after applying a read voltage to the read head, the current at both ends of the read head along the z direction is measured to determine the magnetization direction of the free layer in the magnetic tunnel junction of the read head. If the film structure is a Hall bar, then an excitation current in that direction is applied to the read head through the conductive channel of the spin current generation layer, and after applying a read current to one of the conductive channels, the voltage across the other conductive channel is measured to determine the magnetization direction of the free layer in the magnetic tunnel junction of the read head. (S12) Perform step (S11) multiple times to obtain the probability that the magnetization direction of the free layer is upward when the excitation current in this direction is applied.

6. A magnetic recording device, characterized in that, include: A substrate, and a magnetic recording thin film thereon; The magnetic recording film is circular and includes: a first ferromagnetic layer, a first intermediate layer and a second ferromagnetic layer stacked sequentially; The easy magnetization directions of the two ferromagnetic layers are along the planar direction and the perpendicular direction, respectively; each ferromagnetic layer is used to store one binary information, and different magnetization directions within the ferromagnetic layer correspond to different values ​​of the binary information. The first intermediate layer is made of a non-magnetic material.

7. The magnetic recording device as described in claim 6, characterized in that, A soft magnetic layer is also included between the substrate and the magnetic recording thin film.

8. A multi-state magnetic disk comprising the magnetic recording apparatus of claim 6 or 7, characterized in that, Also includes: A read head, a write head, and magnetic shielding layers located on both sides of the read head; The read head includes a spin flow generation layer and a film structure; the spin flow generation layer is cross-shaped and has two mutually perpendicular conductive channels, one of which is along the y-direction; the film structure is a magnetic tunnel junction, a spin valve, or a Hallbar; each film layer in the read head is parallel to the magnetic recording film, and the film structure faces the magnetic recording film; The write head includes: a vertical magnetic pole, two first horizontal magnetic poles symmetrically arranged about the vertical magnetic pole, and a coil wound around each magnetic pole; the line connecting the two first horizontal magnetic poles is along the y-direction; when the multi-state disk rotates, the read head and the write head move relative to the disk surface along the y-direction; Wherein, the y-direction is parallel to the surface of the magnetic recording film and along the tangential direction.

9. The method for reading and writing a multi-state disk as described in claim 8, characterized in that, include: Write phase; The writing phase includes: Preprocessing steps: Based on the mapping relationship between stored information and magnetization direction, determine the magnetization directions of ferromagnetic layer p and ferromagnetic layer z after the information to be written is written, and denoted as the first magnetization direction and the second magnetization direction, respectively; ferromagnetic layer p and ferromagnetic layer z are the ferromagnetic layers in the magnetic recording film whose easy magnetization direction is along the planar direction and perpendicular direction, respectively. Y-direction writing step: Apply current to a pair of coils wound around two first horizontal magnetic poles to generate a writing magnetic field in the y direction, so that the magnetization direction of the ferromagnetic layer p is the first magnetization direction; z-direction writing step: Apply current to the coil wound on the vertical magnetic pole to generate a writing magnetic field in the z direction, so that the magnetization direction of the ferromagnetic layer z is the second magnetization direction; The z-direction is perpendicular to the surface of the magnetic recording film.

10. The read / write method as described in claim 9, characterized in that, Also includes: Reading stage; The readout stage includes: (T1) Calculate the probability P that the magnetization direction of the free layer is upward when an excitation current is applied in the positive y-axis direction. up (+J y And the probability P that the free layer magnetization direction is upward when an excitation current is applied in the negative y-axis direction. up (-J y ); The free layer is the free layer in the magnetic tunnel junction of the read head; (T2) Calculate the y-direction component H of the leakage magnetic field. y and z-direction component H z The probability P up (H y ) and P up (H z The calculation formula is as follows: (T3) Based on the pre-calibrated correspondence between the components of the leakage magnetic field in each direction and the probability, determine the y-direction component H of the leakage magnetic field. y and z-direction component H z The magnetization direction of the corresponding ferromagnetic layer is determined based on the direction of each component of the leakage magnetic field. In step (T1), for any direction, the probability of the free layer magnetization direction phase when an excitation current is applied in that direction is statistically analyzed, including: (T11) If the film structure is a magnetic tunnel junction or a spin valve, then an excitation current in that direction is applied to the read head through the conductive channel of the spin current generation layer, and after applying a read voltage to the read head, the current at both ends of the read head along the z direction is measured to determine the magnetization direction of the free layer in the magnetic tunnel junction of the read head. If the film structure is a Hall bar, then an excitation current in that direction is applied to the read head through the conductive channel of the spin current generation layer, and after applying a read current to one of the conductive channels, the voltage across the other conductive channel is measured to determine the magnetization direction of the free layer in the magnetic tunnel junction of the read head. (T12) Perform the above step (T11) multiple times to obtain the probability that the magnetization direction of the free layer is upward when the excitation current in this direction is applied.

Images