A FeCoCr / Al magnetic code disk material and its preparation method and application

Abstract

The present invention relates to the technical field of magnetic code disk materials, and specifically discloses a FeCoCr / Al magnetic code disk material, a preparation method thereof, and an application thereof. The FeCoCr / Al magnetic code disk material comprises a substrate, a FeCoCr film, and an Al2O3 layer stacked in sequence, wherein the FeCoCr film comprises α-FeCoCr, γ-FeCoCr, and Co-Al alloy particles. The FeCoCr / Al magnetic code disk material provided by the present invention achieves a high coercive force, with an increase of up to 72% relative to the coercive force of a single FeCoCr film, meeting the practical application requirements of magnetic encoder code disks. At the same time, the dense Al2O3 passivation layer formed on the surface of the material makes the final device more environmentally compatible, thereby improving the service life of the device.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic code disk materials, and in particular to a FeCoCr / Al magnetic code disk material and a preparation method and application thereof. Background Art

[0002] A magnetic encoder detects magnetic field changes to determine rotational position and converts this information into an electrical signal for output. The core components of a magnetic encoder are a magnetic code disk (which records high-density, uniform NS magnetic pole signals) and a sensor chip (which reads the signals). The magnetic properties of the code disk material directly impact the encoder's storage density and stability. High-performance and uniform magnetic materials are crucial for achieving a uniform, multi-pole output sinusoidal signal after magnetization, ensuring encoder accuracy. In applications such as CNC machine tools and textile machinery, magnetic encoders are often exposed to moisture, oil, debris, and oil contamination, placing high demands on the code disk's interference resistance. High coercivity of the code disk material improves its resistance to external electromagnetic interference. Furthermore, the lifespan of the magnetic encoder must also be considered in harsh environments. At present, the coercivity of single-layer FeCoCr materials is still difficult to meet the application requirements of high anti-interference capabilities. If heavy metal protection is used for the film, the cost is high, and as the special environment changes during the application service process, it will fail, resulting in high maintenance costs and even inevitable losses. In the existing technology, the magnetic properties of the film are usually improved by optimizing the heat treatment system, sputtering process, etc., but these methods often only consider the magnetic properties of the material, but ignore the requirements of the material usage scenario. Therefore, obtaining a simple preparation process, low cost, and taking into account the application service life is one of the key issues that need to be solved in this material field.

[0003] Therefore, the existing technology still needs to be improved and developed. Summary of the Invention

[0004] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a FeCoCr / Al magnetic code disk material and its preparation method and application, aiming to solve the problem that the existing single-layer FeCoCr film has low coercive force when used as a magnetic code disk material, resulting in limited application scenarios and short service life.

[0005] The technical solutions of the present invention are as follows:

[0006] A FeCoCr / Al magnetic code disk material comprises a substrate, a FeCoCr film and an Al2O3 layer stacked in sequence, wherein the FeCoCr film comprises α-FeCoCr, γ-FeCoCr and Co-Al alloy particles.

[0007] The FeCoCr / Al magnetic code disk material, wherein the thickness of the Al2O3 layer is 2-4nm.

[0008] The FeCoCr / Al magnetic code disk material, wherein the substrate is one of a glass substrate and a silicon substrate.

[0009] A method for preparing the FeCoCr / Al magnetic code disk material according to the present invention comprises the following steps:

[0010] The FeCoCr layer was deposited on the substrate surface by magnetron sputtering with FeCoCr as target;

[0011] An Al layer is deposited on the surface of the FeCoCr layer by a magnetron sputtering method using Al as a target to obtain a FeCoCr / Al heterostructure;

[0012] The FeCoCr / Al heterostructure is subjected to vacuum annealing to obtain the FeCoCr / Al magnetic code disk material.

[0013] The preparation method of the FeCoCr / Al magnetic code disk material, wherein in the step of depositing the FeCoCr layer on the substrate surface by magnetron sputtering with FeCoCr as the target material, the sputtering power is 30-50W, the vacuum degree of the sputtering chamber is 1×10 -5 -3×10 -5 Pa, the working gas is argon, and the argon pressure is 0.3-0.4Pa.

[0014] In the method for preparing the FeCoCr / Al magnetic code disk material, the element mass ratio of Fe, Co, and Cr in the target material FeCoCr is 40-50:25-30:20-30; and the thickness of the prepared FeCoCr layer is 50-150 nm.

[0015] The preparation method of the FeCoCr / Al magnetic code disk material, wherein in the step of depositing an Al layer on the surface of the FeCoCr layer by magnetron sputtering using Al as a target material, the sputtering power is 50-100W, the vacuum degree of the sputtering chamber is 1×10 -5 -3×10 -5 Pa, the working gas is argon, and the argon pressure is 0.2-0.4Pa.

[0016] In the method for preparing the FeCoCr / Al magnetic code disk material, the thickness of the Al layer is 5-10 nm.

[0017] The preparation method of the FeCoCr / Al magnetic code disk material, wherein in the step of vacuum annealing the FeCoCr / Al heterostructure, the annealing temperature is 645-655°C, the annealing time is 25-35min, and the annealing vacuum degree is 1×10-5 -5×10 -5 Pa.

[0018] An application of the FeCoCr / Al magnetic code disk material according to the present invention is to use the FeCoCr / Al magnetic code disk material to prepare a magnetic encoder.

[0019] Beneficial Effects: The FeCoCr / Al magnetic code disk material provided by this invention achieves a high coercivity, with a coercivity increase of up to 72% compared to that of a single FeCoCr film, meeting the practical application requirements of magnetic encoder code disks. Furthermore, the dense Al2O3 passivation layer formed on the material's surface enhances the environmental compatibility of the final device, extending its service life. The preparation method provided by this invention is simple, efficient, and low-cost, significantly increasing the coercivity of the thin film material, providing a scientific basis for the practical application of thin-film magnetic code disks and their environmental adaptability in complex scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a flow chart of a method for preparing a FeCoCr / Al magnetic code disk material according to the present invention.

[0021] Figure 2 This is the in-plane hysteresis loop of the magnetic code disk material prepared in Example 1.

[0022] Figure 3 This is the in-plane hysteresis loop of the magnetic code disk material prepared in Comparative Example 5.

[0023] Figure 4 This is the in-plane hysteresis loop of the magnetic code disk material prepared in Comparative Example 6.

[0024] Figure 5 1 and 2 are XRD patterns of the FeCoCr / Al magnetic code disk material (denoted as b) prepared in Example 1 and the single-layer FeCoCr thin film material (denoted as a) in Comparative Example 6. DETAILED DESCRIPTION

[0025] The present invention provides a FeCoCr / Al magnetic code disk material, its preparation method, and application. To make the objectives, technical solutions, and effects of the present invention more clear and explicit, the present invention is further described below. It should be understood that the specific embodiments described herein are only intended to illustrate the present invention and are not intended to limit the present invention.

[0026] See also Figure 1 , Figure 1 The present invention provides a flow chart of a method for preparing a FeCoCr / Al magnetic code disk material, as shown in the figure, which includes the following steps:

[0027] S10, depositing a FeCoCr layer on the substrate surface by magnetron sputtering using FeCoCr as a target;

[0028] S20, depositing an Al layer on the surface of the FeCoCr layer by a magnetron sputtering method using Al as a target to obtain a FeCoCr / Al heterostructure;

[0029] S30 , performing vacuum annealing on the FeCoCr / Al heterostructure to obtain the FeCoCr / Al magnetic code disk material.

[0030] Specifically, during vacuum annealing, the FeCoCr / Al heterostructure causes some Al atoms in the Al layer to diffuse from the surface into the FeCoCr layer. This, through the stripe decomposition effect, separates the FeCo-rich phase in the original α-FeCoCr into smaller regions. This structure effectively splits the originally continuous magnetic phase into multiple independent small magnetic domains, reducing mutual interference between the domains. Simultaneously, the diffusion of Al atoms promotes the formation of the γ-FeCoCr phase, resulting in finer FeCoCr grains, further enhancing the isolation of the magnetic phases. According to magnetic principles, small, isolated magnetic phases reduce the synergistic effect of magnetic moment reversals, thereby improving coercivity.

[0031] During the annealing process, Al atoms that did not diffuse into the FeCoCr layer aggregate and oxidize on the FeCoCr surface, forming a dense α-Al2O3 passivation layer. Al2O3 is a typical non-magnetic oxide. The physical pinning points it forms on the surface or interface hinder the movement of magnetic domain walls, which is a key process in magnetic moment reversal. The pinning effect of Al2O3 increases the resistance to domain wall movement, directly leading to an increase in coercivity.

[0032] During annealing, the diffusion activities of various metal atoms within the FeCoCr layer vary. Co's diffusion coefficient at high temperatures is more compatible with Al atoms. Furthermore, the crystal structure of Co (face-centered cubic) closely matches that of Al (face-centered cubic), resulting in a smaller lattice constant difference. Consequently, Al atoms that diffuse into the FeCoCr layer combine with Co to form nanoscale dispersed Co-Al alloy particles, primarily located at the interface between the FeCoCr and Al layers. These Co-Al alloy particles possess high hardness and low magnetization. These nanoparticles act as obstacles to domain wall motion, increasing the energy required for magnetization reversal and widening the hysteresis loop. Furthermore, the Co-Al particles pin grain boundaries, preventing FeCoCr grain coarsening during annealing, further enhancing coercivity. The Co-Al reaction reduces the Co content in the FeCoCr layer, altering the local composition and inducing phase separation. This promotes stripe decomposition of the FeCoCr layer, forming a nanoscale alternating structure of FeCo-rich regions (high magnetic moment) and Cr-rich regions (non-magnetic), further enhancing the magnetic hardening effect.

[0033] The present invention achieves a 72% increase in the coercivity of the FeCoCr film before the Al layer is introduced through a three-level regulation method of element selective reaction, phase separation, and interface self-assembly, while maintaining a good remanence level to meet practical application requirements; the surface Al2O3 passivation layer can also isolate the corrosive medium and maintain environmental stability.

[0034] In some embodiments, in the step of depositing a FeCoCr layer on the substrate surface by magnetron sputtering using FeCoCr as a target, the sputtering power is 30-50W, the vacuum degree of the sputtering chamber is 1×10 -5 -3×10 -5 Pa, the working gas is argon, and the argon pressure is 0.3-0.4 Pa. In this embodiment, the element mass ratio of Fe, Co, and Cr in the target material FeCoCr is 40-50:25-30:20-30, and the thickness of the FeCoCr layer is 50-150nm. As an example, the target material FeCoCr includes, by mass percentage, 45% iron, 30% Co, and 25% Cr; the thickness of the FeCoCr layer can be 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 110nm, 120nm, 130nm, 140nm, 150nm, etc., but is not limited thereto. In this embodiment, the thickness of the FeCoCr layer is controlled by controlling the magnetron sputtering time.

[0035] In some embodiments, in the step of depositing an Al layer on the surface of the FeCoCr layer by magnetron sputtering using Al as a target, the sputtering power is 50-100 W, the vacuum degree of the sputtering chamber is 1×10 -5-3×10 -5 Pa, the working gas is argon, and the argon pressure is 0.2-0.4 Pa. The thickness of the Al layer is 5-10 nm. For example, the thickness of the Al layer can be 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, etc., but is not limited thereto. This embodiment controls the thickness of the Al layer by controlling the magnetron sputtering time. In this embodiment, the purpose of setting the thickness of the Al layer to 5-10 nm is to balance the dual requirements of coercive force improvement and protective performance, while avoiding performance degradation caused by improper thickness. Specifically, one of the core functions of the Al layer is to enter the FeCoCr layer through atomic diffusion during annealing to induce the formation of γ-FeCoCr phase (refine the grains) and isolate the magnetic phase, thereby improving the coercive force. If the thickness of the Al layer is less than 5nm, the total amount of Al atoms is insufficient, and the number of Al atoms diffused into the FeCoCr layer during annealing is limited, which cannot fully induce the formation of the γ-FeCoCr phase and it is difficult to effectively isolate the FeCo-rich phase, resulting in insufficient increase in coercivity. If the thickness of the Al layer is greater than 10nm, too many Al atoms may excessively diffuse into the FeCoCr layer, diluting the concentration of magnetic elements (Fe, Co) and destroying the stability of the magnetic moment arrangement. At the same time, excessive Al may form non-magnetic agglomerates in the FeCoCr layer, which in turn reduces the remanence level. A thickness of 5-10nm can provide an appropriate amount of Al atoms, which can not only meet the diffusion requirements and improve the coercivity by inducing the γ-FeCoCr phase and isolating the magnetic phase, but also will not cause the magnetic properties to deteriorate due to excessive Al, and take into account the balance between coercivity and remanence.

[0036] Another key function of the Al layer is to in-situ generate a nanometer-scale, dense Al2O3 passivation layer on the surface, forming a physical barrier against environmental corrosion. If the thickness is less than 5nm, the surface lacks oxidizable Al atoms, and the resulting Al2O3 passivation layer may be porous or discontinuous (failure to form a defect-free physical barrier). Environmental media such as moisture and oil can easily penetrate the film and corrode the FeCoCr substrate, reducing the life of the magnetic code disk. If the thickness exceeds 10nm, the excessive thickness of the Al2O3 passivation layer may generate internal stress, leading to film cracking and compromising the protective integrity. Furthermore, an excessively thick Al layer increases the overall thickness of the film, potentially compromising the thinness and lightweight requirements of magnetic encoders (magnetic code disks must accommodate precise structures). A thickness of 5-10nm produces a continuous, defect-free Al2O3 passivation layer. This moderate film thickness (nanometer-scale) provides high density and low internal stress, effectively blocking environmental media corrosion while ensuring a stable bond between the film and the substrate, significantly extending the service life of the magnetic code disk under complex operating conditions (such as moisture and oil).

[0037] In some embodiments, in the step of vacuum annealing the FeCoCr / Al heterostructure, the annealing temperature is 645-655°C, the annealing time is 25-35 minutes, and the annealing vacuum degree is 1×10 -5 -5×10 -5 Pa.

[0038] In this embodiment, the core objective of the annealing treatment is to ensure effective diffusion of Al atoms and induce the formation of the γ-FeCoCr phase, while avoiding excessive diffusion that would degrade magnetic properties. Sufficient thermal activation energy is required for Al atoms to diffuse from the surface into the FeCoCr layer. If the temperature is below 645°C, insufficient thermal energy results, resulting in slow and shallow diffusion of Al atoms. This prevents Al atoms from fully penetrating the FeCoCr layer to achieve stripe decomposition (separating the FeCo-rich phase) and the formation of the γ-FeCoCr phase. This results in poor magnetic phase isolation and insufficient coercivity improvement (failure to reach the target value of 671 Oe). If the temperature is above 655°C, excessive Al diffusion may lead to excessive dilution of the magnetic phases (Fe and Co) in the FeCoCr layer with Al, destabilizing the magnetic moment alignment. Furthermore, excessively high temperatures can lead to coarsening of the γ-FeCoCr grains, negating the advantage of grain refinement and potentially blurring the interface between the FeCoCr layer and the Al layer, which in turn reduces coercivity. The temperature of 645-655°C selected in this embodiment can balance diffusion efficiency and structural stability. It can provide sufficient energy for Al atoms to diffuse into the FeCoCr layer and induce the formation of the γ-FeCoCr phase (refining the grains and isolating the magnetic phase), while avoiding the degradation of magnetic properties caused by excessive diffusion, ultimately ensuring that the coercivity is stably increased to about 671 Oe.

[0039] In this embodiment, the annealing time is controlled within 25-35 minutes to ensure sufficient Al diffusion, phase formation, and surface oxidation, while also avoiding structural degradation caused by excessive annealing time. Al atomic diffusion, γ-FeCoCr phase formation, and the formation of the surface Al2O3 oxide layer all require a certain amount of time. If the annealing time is shorter than 25 minutes, Al atoms will not diffuse sufficiently (not fully entering the FeCoCr layer), resulting in insufficient γ-FeCoCr phase formation. Furthermore, the surface Al2O3 layer may have low density (porosity) due to insufficient oxidation time, failing to achieve the dual effects of magnetic phase isolation and physical barrier. If the annealing time is longer than 35 minutes, Al atoms may diffuse excessively deep into the FeCoCr layer, resulting in excessive segmentation of the magnetic phase (even disrupting the continuous magnetic moment), which in turn reduces the remanence level. Furthermore, the surface Al2O3 layer may thicken and crack (increase internal stress) due to excessive oxidation, losing its density and failing to effectively protect the substrate. This embodiment experimentally verified that selecting a time period of 25-35 min ensures that: Al atoms diffuse to the target depth and induce the formation of the γ-FeCoCr phase (meeting the requirement for increased coercivity); the surface Al2O3 layer is completely oxidized and has a density of nanometers (no defects), forming an effective physical barrier, while avoiding damage to the magnetic properties and the oxide layer caused by excessive reaction.

[0040] In this embodiment, the annealing vacuum degree is selected to be 1×10 -5 -5×10 -5 The core goal of Pa is to prevent the oxidation degradation of the FeCoCr layer and ensure the density of the surface Al2O3 layer. FeCoCr is an easily oxidized metal. If the vacuum degree is insufficient (higher than 5×10 -5 Pa, that is, low vacuum), impurity gases such as O2 and N2 remaining in the furnace will react with the FeCoCr layer to generate non-magnetic oxides such as FeO and Cr2O3, destroying the magnetic phase structure and causing a significant decrease in coercivity and remanence; since the formation of the surface Al2O3 layer requires a small amount of oxygen (from the residual oxygen adsorbed on the film surface or trace oxygen in the furnace): if the vacuum is too high (less than 1×10 -5 Pa, which is close to absolute vacuum), the oxygen content in the furnace is too low, and the Al atoms cannot be fully oxidized to form Al2O3, resulting in the loss of the surface protective layer and the inability to form a physical barrier, which reduces the environmental adaptability of the magnetic code disk. -5 -5×10 -5 The vacuum degree of Pa can achieve dual protection: preventing the FeCoCr layer from being oxidized by impurity gases (ensuring the integrity of the magnetic phase structure); providing an appropriate amount of oxygen to allow the surface Al atoms to oxidize to form dense Al2O3 (nanoscale density), achieving corrosion protection for the substrate, and ultimately improving the service life of the magnetic code disk under complex working conditions.

[0041] In some embodiments, the FeCoCr / Al magnetic code disk material prepared based on the method of the present invention includes a substrate, a FeCoCr film and an Al2O3 layer stacked in sequence, and the FeCoCr film includes α-FeCoCr, γ-FeCoCr and Co-Al alloy particles.

[0042] Specifically, in the FeCoCr film, γ-FeCoCr is induced by the diffusion of Al atoms, and its grain size is small and separated by Al atoms (strip decomposition effect), which reduces the magnetic moment interference between magnetic phases and provides a basis for the improvement of coercive force; the residual α-FeCoCr acts as a native magnetic phase, ensuring the basic remanence level of the film; Co-Al alloy particles form non-magnetic pinning points inside the FeCoCr layer and near the interface, hindering the movement of magnetic domain walls and further enhancing the ability to resist magnetic moment reversal; the three together increase the coercive force of the FeCoCr film from 390 Oe to 671 Oe (an increase of 72%), far exceeding the Al / FeCoCr structure (260 Oe), fully meeting the requirements of high-precision magnetic encoders for high coercive force (anti-external electromagnetic interference) and good remanence (stable signal output).

[0043] After annealing, the Al layer oxidizes to form a continuous, defect-free, nanometer-scale dense Al2O3 layer, which acts as a physical barrier to directly block the corrosion of the FeCoCr matrix from environmental media such as moisture and oil. The formation of Co-Al alloy particles also reduces the exposure of easily corrosive elements such as Fe and Cr, while enhancing the overall structural stability of the film (suppressing grain coarsening or interfacial cracking). This combination of surface protection and internal stability significantly improves the service life of the magnetic code disk in complex operating conditions (such as the oily and moisture-prone environments of CNC machine tools and textile machinery), reducing the risk of functional failure.

[0044] In some embodiments, the Al2O3 layer has a thickness of 2-4 nm. In this embodiment, a thickness of 2-4 nm allows for a defect-free, high-density Al2O3 layer that completely covers the substrate surface while preventing stress cracking and effectively shielding against environmental corrosion, significantly extending the service life of the magnetic encoder in complex operating conditions (such as oily and water-vapor environments). The core function of the magnetic encoder is to detect position using changes in the magnetic signal of the FeCoCr film. As a non-magnetic oxide, the thickness of Al2O3 must avoid shielding or attenuating the magnetic field. The ultra-thin thickness of 2-4 nm, well below the critical penetration threshold for magnetic signals (excessive thickness of the non-magnetic layer attenuates magnetic field strength), ensures no significant loss of the magnetic signal (such as remanence and magnetic field distribution) from the FeCoCr film, ensuring accurate readings by the magnetic encoder. A thickness exceeding 4 nm may attenuate the magnetic signal due to the excessive thickness of the non-magnetic layer, compromising detection accuracy. A thickness below 2 nm, while not affecting the magnetic signal, fails to provide continuous protection and may indirectly degrade magnetic properties due to substrate corrosion. Therefore, this thickness range achieves a balance between protection function and magnetic signal integrity, ensuring that the coercivity is improved (671 Oe) and the remanence is stable without interfering with the signal output in practical applications.

[0045] In some embodiments, the substrate is one of a glass substrate and a silicon substrate, but is not limited thereto.

[0046] In some embodiments, a use of the FeCoCr / Al magnetic code disk material according to the present invention is further provided, wherein the FeCoCr / Al magnetic code disk material is used to prepare a magnetic encoder.

[0047] The present invention will be further explained below by means of specific embodiments:

[0048] Example 1

[0049] A method for preparing a FeCoCr / Al magnetic code disk material comprises the following steps:

[0050] The FeCoCr layer was deposited on the surface of the glass substrate by magnetron sputtering using FeCoCr as the target material, wherein the elements in the target material FeCoCr include, by mass percentage, 45% iron, 30% Co, and 25% Cr; the sputtering power was 40W, and the vacuum degree of the sputtering chamber was 3×10 -5 Pa, the working gas is argon, and the argon pressure is 0.4 Pa; the thickness of the FeCoCr layer is 100 nm by controlling the sputtering time;

[0051] The Al layer was deposited on the surface of the FeCoCr layer by magnetron sputtering with Al as the target to obtain a FeCoCr / Al heterostructure. The sputtering power was 80W and the vacuum degree of the sputtering chamber was 3×10 -5Pa, the working gas is argon, and the argon pressure is 0.3 Pa; wherein, the thickness of the Al layer is 8 nm by controlling the sputtering time;

[0052] The FeCoCr / Al heterostructure was subjected to vacuum annealing treatment, wherein the annealing temperature was 650°C, the annealing time was 30 min, and the annealing vacuum degree was 3×10 -5 Pa, to prepare the FeCoCr / Al magnetic code disk material.

[0053] Example 2

[0054] A method for preparing a FeCoCr / Al magnetic code disk material comprises the following steps:

[0055] The FeCoCr layer was deposited on the surface of the glass substrate by magnetron sputtering using FeCoCr as the target material, wherein the elements in the target material FeCoCr include, by mass percentage, 45% iron, 30% Co, and 25% Cr; the sputtering power was 40W, and the vacuum degree of the sputtering chamber was 3×10 -5 Pa, the working gas is argon, and the argon pressure is 0.4 Pa; the thickness of the FeCoCr layer is 50 nm by controlling the sputtering time;

[0056] The Al layer was deposited on the surface of the FeCoCr layer by magnetron sputtering with Al as the target to obtain a FeCoCr / Al heterostructure. The sputtering power was 80W and the vacuum degree of the sputtering chamber was 3×10 -5 Pa, the working gas is argon, and the argon pressure is 0.3 Pa; wherein, the thickness of the Al layer is 5 nm by controlling the sputtering time;

[0057] The FeCoCr / Al heterostructure was subjected to vacuum annealing treatment, wherein the annealing temperature was 645°C, the annealing time was 35 min, and the annealing vacuum degree was 3×10 -5 Pa, to prepare the FeCoCr / Al magnetic code disk material.

[0058] Example 3

[0059] A method for preparing a FeCoCr / Al magnetic code disk material comprises the following steps:

[0060] The FeCoCr layer was deposited on the surface of the silicon substrate by magnetron sputtering using FeCoCr as the target material, wherein the elements in the target material FeCoCr include, by mass percentage, 45% iron, 30% Co and 25% Cr; the sputtering power was 40W, and the vacuum degree of the sputtering chamber was 3×10 -5 Pa, the working gas is argon, and the argon pressure is 0.4 Pa; the thickness of the FeCoCr layer is 150 nm by controlling the sputtering time;

[0061] The Al layer was deposited on the surface of the FeCoCr layer by magnetron sputtering with Al as the target to obtain a FeCoCr / Al heterostructure. The sputtering power was 80W and the vacuum degree of the sputtering chamber was 3×10 -5 Pa, the working gas is argon, and the argon pressure is 0.3 Pa; wherein, the thickness of the Al layer is 10 nm by controlling the sputtering time;

[0062] The FeCoCr / Al heterostructure was subjected to vacuum annealing treatment, wherein the annealing temperature was 655°C, the annealing time was 25 min, and the annealing vacuum degree was 3×10 -5 Pa, to prepare the FeCoCr / Al magnetic code disk material.

[0063] Comparative Example 1

[0064] Comparative Example 1 provides a method for preparing a FeCoCr / Al magnetic code disk material. The preparation steps thereof are different from those of Example 1 only in that the thickness of the Al layer is set to 3 nm by controlling the sputtering time. The remaining steps are the same as those of Example 1.

[0065] Comparative Example 2

[0066] Comparative Example 2 provides a method for preparing a FeCoCr / Al magnetic code disk material. The preparation steps thereof are different from those of Example 1 only in that the thickness of the Al layer is set to 12 nm by controlling the sputtering time. The remaining steps are the same as those of Example 1.

[0067] Comparative Example 3

[0068] Comparative Example 3 provides a method for preparing a FeCoCr / Al magnetic code disk material. The preparation steps thereof are different from those of Example 1 only in that the annealing temperature is 550° C., and the remaining steps are the same as those of Example 1.

[0069] Comparative Example 4

[0070] Comparative Example 4 provides a method for preparing a FeCoCr / Al magnetic code disk material. The preparation steps thereof are different from those of Example 1 only in that the annealing temperature is 700° C., and the remaining steps are the same as those of Example 1.

[0071] Comparative Example 5

[0072] A method for preparing an Al / FeCoCr magnetic code disk material comprises the following steps:

[0073] The Al layer was deposited on the substrate surface by magnetron sputtering with Al as target. The sputtering power was 80W and the vacuum degree of the sputtering chamber was 3×10 -5 Pa, the working gas is argon, and the argon pressure is 0.3 Pa; wherein, the thickness of the Al layer is 8 nm by controlling the sputtering time;

[0074] The FeCoCr layer was deposited on the Al layer surface by magnetron sputtering using FeCoCr as the target material to obtain an Al / FeCoCr heterostructure, wherein the elements in the FeCoCr target material include, by mass percentage, 45% iron, 30% Co, and 25% Cr; the sputtering power was 40W, and the vacuum degree of the sputtering chamber was 3×10 -5 Pa, the working gas is argon, and the argon pressure is 0.4 Pa; the thickness of the FeCoCr layer is 100 nm by controlling the sputtering time;

[0075] The Al / FeCoCr heterostructure was subjected to vacuum annealing treatment, wherein the annealing temperature was 650°C, the annealing time was 30 min, and the annealing vacuum degree was 3×10 -5 Pa, to prepare the Al / FeCoCr magnetic code disk material.

[0076] Comparative Example 6

[0077] A method for preparing a magnetic code disk material comprises the following steps:

[0078] The FeCoCr layer was deposited on the substrate surface by magnetron sputtering using FeCoCr as the target material, wherein the elements in the target material FeCoCr included, by mass percentage, 45% iron, 30% Co, and 25% Cr; the sputtering power was 40W, and the vacuum degree of the sputtering chamber was 3×10 -5 Pa, the working gas is argon, and the argon pressure is 0.4 Pa; the thickness of the FeCoCr layer is 100 nm by controlling the sputtering time;

[0079] The FeCoCr layer was subjected to vacuum annealing treatment, wherein the annealing temperature was 650°C, the annealing time was 30 min, and the annealing vacuum degree was 3×10 -5 Pa, the magnetic code disk material is prepared.

[0080] The in-plane hysteresis loops (MH curves) of the magnetic code disk materials obtained in Example 1 and Comparative Examples 5-6 were tested. The results are as follows: Figure 2-4 As shown, the horizontal axis of the MH curve is the external magnetic field intensity (H, unit kOe), the vertical axis is the magnetization intensity (M), and the magnetic field intensity at the intersection of the curve and the horizontal axis is the coercive force (the reverse magnetic field required for magnetic moment reversal. The larger the value, the stronger the anti-interference ability).

[0081] Figure 2 is the in-plane hysteresis loop of the magnetic code disk material obtained in Example 1. Figure 2It can be seen that its coercive force reaches 671 Oe, and the "squareness" of the curve is good (the ratio of remanence to saturation magnetization intensity is high), indicating that while maintaining a high coercive force, it also maintains a good level of remanence, fully meeting the requirements of high-precision magnetic encoders for resisting electromagnetic interference and stabilizing signal output.

[0082] Figure 3 The in-plane hysteresis loop of the magnetic code disk material obtained in Comparative Example 5 is shown in FIG. Figure 3 It can be seen that its coercivity is only 260 Oe, which is not only lower than the 671 Oe in Figure 2 (an increase of 158%), but also lower than Figure 4 The coercivity of a single FeCoCr layer (390 Oe) is shown in Figure 2. This demonstrates the structural necessity of the Al layer as the top layer. When Al is the bottom layer, it is covered by the FeCoCr layer and cannot effectively diffuse into the FeCoCr layer to induce phase structure optimization. It also cannot form an Al2O3 passivation layer on the surface. Instead, the Al layer hinders the continuity of the magnetic phase, resulting in a decrease in coercivity.

[0083] Figure 4 The in-plane hysteresis loop of the magnetic code disk material obtained in Comparative Example 6 is shown in FIG. Figure 4 As can be seen, its coercivity is only 390 Oe, far lower than the 671 Oe (72% increase) in Figure 2. This demonstrates that the introduction of the Al layer is key to improving coercivity. Without the Al layer, the FeCoCr film cannot induce γ-FeCoCr formation and Al2O3 pinning through Al diffusion, resulting in a coercivity that is insufficient for practical applications.

[0084] Figure 5 The XRD patterns of the FeCoCr / Al magnetic code disk material (denoted as b) prepared in Example 1 and the single-layer FeCoCr film material (denoted as a) in Comparative Example 6 are shown in Figure 1. The horizontal axis represents the diffraction angle, and the vertical axis represents the diffraction intensity (reflecting the presence of the crystalline phase). The diffraction peaks 1-4 correspond to Co-Al alloy, γ-FeCoCr, α-FeCoCr, and α-Al2O3, respectively. Figure 5 It can be seen that γ-FeCoCr (peak 2) and α-Al2O3 (peak 4) are detected in the (b) FeCoCr / Al magnetic code disk material, while these two phases are not present in (a), proving that the introduction of the Al layer promotes the formation of γ-FeCoCr (refining the grains and isolating the magnetic phase) and Al2O3 (domain wall pinning), explaining the mechanism of enhanced coercivity from a microstructural perspective; a Co-Al alloy peak (peak 1) is also detected in (b), proving that Al atoms preferentially combine with Co to form alloy particles, further enhancing the coercivity by pinning the magnetic domain walls and inhibiting grain coarsening.

[0085] The magnetic code disk materials prepared in Examples 1-3 and Comparative Examples 1-5 were tested for coercivity, remanence ratio, and coercivity retention after a 48-hour salt spray test. The results are shown in Table 1:

[0086] Table 1 Performance test results

[0087]

[0088] It can be seen from the data in Table 1 that the parameters of Examples 1-3 are all within the optimal range (Al layer 5-10nm, annealing 645-655℃, etc.), the coercivity is stable at 658-671Oe (increase of 70%-72%), the remanence ratio is ≥0.78 (maintaining good magnetic signal output capability), and the coercivity retention rate after the salt spray test is ≥91% (resistant to complex environmental corrosion), fully meeting the requirements of high-precision magnetic encoders.

[0089] Compared with Example 1, the coercivity and corrosion resistance of the FeCoCr / Al magnetic code disk material prepared in Comparative Example 1 are significantly reduced. This is because the Al layer in Comparative Example 1 is only 3 nm, and the total amount of Al atoms it provides is insufficient. During annealing, few Al atoms diffuse into the FeCoCr layer, which cannot fully induce the formation of γ-FeCoCr (refine the grains and isolate the magnetic phase). In addition, the generation of Co-Al alloy particles is insufficient, and the pinning effect of the magnetic domain wall is weak, resulting in insufficient increase in coercivity (only 420 Oe); the corrosion resistance is reduced: the Al layer is too thin, resulting in insufficient Al atoms that can be oxidized on the surface, and the generated Al2O3 layer has pores (discontinuous). In the salt spray test, water vapor and salt easily penetrate the film layer to corrode the FeCoCr matrix, and the coercivity retention rate is only 75%.

[0090] Compared with Example 1, the coercive force, remanence ratio and corrosion resistance of the FeCoCr / Al magnetic code disk material prepared in Comparative Example 2 also decreased significantly. This is because the Al layer in Comparative Example 2 is too thick (12 nm), which causes Al atoms to diffuse excessively into the FeCoCr layer during annealing, diluting the concentration of magnetic elements such as Fe and Co, destroying the continuity of the magnetic moment arrangement, and the remanence ratio decreases from 0.82 to 0.65; at the same time, excessive Al forms non-magnetic agglomerates, hindering the arrangement of magnetic domains, and the coercive force decreases to 510 Oe; the corrosion resistance decreases: the surface Al2O3 layer thickens due to excessive Al, and the internal stress increases, causing the film layer to crack. In the salt spray test, the corrosive medium invades from the cracks, and the retention rate drops to 82%.

[0091] Compared with Example 1, the coercive force and corrosion resistance of the FeCoCr / Al magnetic code disk material prepared in Comparative Example 3 are significantly reduced. This is because the temperature in Comparative Example 3 is too low (550°C) to provide sufficient energy to drive the diffusion of Al atoms. The amount of γ-FeCoCr generated in the FeCoCr layer is extremely small, the magnetic phase is not effectively isolated, and the coercive force is insufficiently improved (450Oe); however, the Fe and Co magnetic phases are not destroyed, and the remanence ratio is basically maintained; the corrosion resistance is reduced: the low temperature leads to insufficient oxidation of the surface Al, the density of the Al2O3 layer is low (pores exist), the corrosive medium is easily penetrated, and the retention rate is reduced to 80%.

[0092] Compared with Example 1, the coercivity, remanence ratio and corrosion resistance of the FeCoCr / Al magnetic code disk material prepared in Comparative Example 4 are significantly reduced. This is because the high temperature (700°C) in Comparative Example 4 causes excessive diffusion of Al atoms, excessive dilution of the magnetic phases (Fe, Co) in the FeCoCr layer, disordered arrangement of the magnetic moments, and a remanence ratio reduced to 0.60; at the same time, the γ-FeCoCr grains coarsened due to high temperature, lost their refining and isolation effect, and the coercivity dropped to 480Oe, and the corrosion resistance decreased significantly: high temperature causes the FeCoCr layer grains to coarsen (increase in grain boundaries), and the Al2O3 layer cracks due to excessive oxidation. The corrosive medium invades both the grain boundaries and the cracks, and the retention rate is only 70%.

[0093] Compared with Example 1, the coercivity and corrosion resistance of the Al / FeCoCr magnetic code disk material prepared in Comparative Example 5 decreased most significantly. This is because when Al is the bottom layer, it is completely covered by the FeCoCr layer. During annealing, Al atoms cannot diffuse into the FeCoCr layer (the diffusion path is blocked), and cannot induce the formation of γ-FeCoCr. The coercivity is only 260Oe; at the same time, the Al layer cannot protect the FeCoCr surface, the magnetic phase is easily disturbed by the environment, and the remanence ratio drops to 0.55; the corrosion resistance is extremely poor: the Al layer is at the bottom layer, and the Al2O3 protective layer cannot be generated on the FeCoCr surface. The FeCoCr is directly exposed and quickly corroded in the salt spray test, with a retention rate of only 65%.

[0094] Compared with Example 1, the coercivity of the magnetic code disk material prepared in Comparative Example 6 is 390 Oe. Since the FeCoCr film has no Al layer, the Al2O3 passivation layer cannot be generated. The surface has no physical barrier and is easily corroded by water vapor and oil. The coercivity retention rate after 48 hours of salt spray test is about 60%.

[0095] It should be understood that the application of the present invention is not limited to the above examples. For those skilled in the art, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A FeCoCr / Al magnetic code disk material, characterized in that: The invention comprises a substrate, a FeCoCr film and an Al2O3 layer stacked in sequence, wherein the FeCoCr film comprises α-FeCoCr, γ-FeCoCr and Co-Al alloy particles; the thickness of the Al2O3 layer is 2-4 nm; the coercive force of the FeCoCr / Al magnetic code disk material is stable at 658-671 Oe, the remanence ratio is ≥0.78, and the coercive force retention rate after the salt spray test is ≥91%.

2. The FeCoCr / Al magnetic code disk material according to claim 1, characterized in that: The substrate is one of a glass substrate and a silicon substrate.

3. A method for preparing the FeCoCr / Al magnetic code disk material according to claim 1 or 2, characterized in that: Including steps: The FeCoCr layer was deposited on the substrate surface by magnetron sputtering with FeCoCr as target; Depositing an Al layer on the surface of the FeCoCr layer by magnetron sputtering using Al as a target to obtain a FeCoCr / Al heterostructure, wherein the thickness of the Al layer is 5-10 nm; The FeCoCr / Al heterostructure was subjected to vacuum annealing to obtain the FeCoCr / Al magnetic code disk material. The annealing temperature was 645-655°C, the annealing time was 25-35 min, and the annealing vacuum degree was 1×10 -5 -5×10 -5 Pa.

4. The method for preparing the FeCoCr / Al magnetic code disk material according to claim 3, characterized in that: In the step of depositing the FeCoCr layer on the substrate surface by magnetron sputtering with FeCoCr as target, the sputtering power is 30-50W and the vacuum degree of the sputtering chamber is 1×10 -5 -3 × 10 -5 Pa, the working gas is argon, and the argon pressure is 0.3-0.4Pa.

5. The method for preparing the FeCoCr / Al magnetic code disk material according to claim 4, characterized in that: The element mass ratio of Fe, Co and Cr in the target material FeCoCr is 40-50:25-30:20-30; and the thickness of the prepared FeCoCr layer is 50-150 nm.

6. The method for preparing the FeCoCr / Al magnetic code disk material according to claim 3, characterized in that: In the step of depositing an Al layer on the surface of the FeCoCr layer by magnetron sputtering with Al as the target, the sputtering power is 50-100W and the vacuum degree of the sputtering chamber is 1×10 -5 -3×10 -5 Pa, the working gas is argon, and the argon pressure is 0.2-0.4Pa.

7. A use of the FeCoCr / Al magnetic code disk material according to claim 1 or 2, wherein the FeCoCr / Al magnetic code disk material is used to prepare a magnetic encoder.

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