Magnetic memory device and method of operation the same

Abstract

The present invention relates to a magnetic memory device, and more specifically, to a loop-type magnetic track, wherein the magnetic track comprises a first portion and a second portion arranged in a counterclockwise direction; a first conductive line on the upper surface of the first portion; and a second conductive line on the bottom surface of the second portion. The magnetic track comprises a lower magnetic layer, a spacer layer, and an upper magnetic layer stacked sequentially, wherein each of the first and second conductive lines comprises a heavy metal, and each of the first and second conductive lines is configured to generate a spin-orbit torque by a current flowing therein, and the magnetic domains within the magnetic track move in a clockwise or counterclockwise direction by the spin-orbit torque.

Description

Technology Field

[0001] The present invention relates to a magnetic memory device, and more specifically, to a magnetic memory device using spin-orbit torque (SOT) and a method of operating the same. Background Technology

[0002] With the increasing speed and low power consumption of electronic devices, embedded memory devices are also required to perform fast read / write operations and operate at low voltages. Magnetic memory devices are being researched as memory devices that meet these demands. Magnetic memory devices are gaining attention as next-generation memory because they can possess characteristics such as high-speed operation and / or non-volatility. In particular, research and development on new magnetic memory devices utilizing the movement phenomenon of magnetic domain walls in magnetic materials is currently underway. Prior art literature

[65535] US 2021 / 0126189 A1 (April 29, 2021) Ring-shaped Racetrack memory based on spin orbit torque driven chiral domain wall motions, Yue Zhang Et al., Scientific Reports, 11 October 2016 The problem to be solved

[0003] The technical problem that the present invention aims to solve is to provide a magnetic memory device including a loop-type magnetic track.

[0004] Another technical objective of the present invention is to provide a method of operation for a magnetic memory device including a loop-type magnetic track. means of solving the problem

[0005] According to the concept of the present invention, a magnetic memory device comprises a loop-type magnetic track, wherein the magnetic track includes a first portion and a second portion arranged in a counterclockwise direction; a first conductive line on the upper surface of the first portion; and a second conductive line on the bottom surface of the second portion. The magnetic track comprises a lower magnetic layer, a spacer layer, and an upper magnetic layer stacked sequentially, wherein each of the first and second conductive lines comprises a heavy metal, and each of the first and second conductive lines is configured to generate a spin-orbit torque by a current flowing therein, and the magnetic domains within the magnetic track may move in a clockwise or counterclockwise direction by the spin-orbit torque.

[0006] According to another concept of the present invention, a magnetic memory device comprises a loop-type magnetic track, wherein the magnetic track includes a first portion and a second portion arranged in a counterclockwise direction; a first conductive line on the upper surface of the first portion; and a second conductive line on the lower surface of the second portion. The magnetic track comprises a lower magnetic layer, a spacer layer, and an upper magnetic layer stacked sequentially, and each of the first and second conductive lines is configured to generate spin-orbit torque by a current flowing therein, wherein the first conductive line is configured such that the current flows in a clockwise or counterclockwise direction, and the second conductive line is configured such that the current flows in a counterclockwise or clockwise direction, and the direction of the current of the first conductive line may be opposite to the direction of the current of the second conductive line.

[0007] According to another concept of the present invention, in a method of operation of a magnetic memory device, the magnetic memory device may comprise: a loop-type magnetic track, wherein the magnetic track comprises first to fourth portions arranged in a counterclockwise direction, and the first portion and the fourth portion are connected to each other; a first conductive line on the upper surface of the first portion; a second conductive line on the bottom surface of the second portion; a third conductive line on the upper surface of the third portion; and a fourth conductive line on the bottom surface of the fourth portion. Each of the first to fourth conductive lines may be configured to generate a spin-orbit torque by a current flowing therein. The method of operation comprises: a first step of applying a pulse to the first conductive line to move magnetic domains on the first conductive line in a clockwise direction; a second step of applying a pulse to the second conductive line to move magnetic domains on the second conductive line in the clockwise direction; and a third step of applying a pulse to the third conductive line to move magnetic domains on the third conductive line in the clockwise direction. and may include a fourth step of applying a pulse to the fourth conductive line to move magnetic domains on the fourth conductive line in the clockwise direction. The first to fourth steps may be performed sequentially. Effects of the invention

[0008] The magnetic memory device of the present invention can fill most of the area of ​​the magnetic track with magnetic domains by using a loop-type magnetic track. In other words, the present invention can improve the data density of the magnetic memory device.

[0009] The magnetic memory device of the present invention can prevent spin-orbit torque gaps by arranging conductive lines alternately up and down on a magnetic track. This prevents malfunction of the magnetic memory device and improves reliability. Brief explanation of the drawing

[0010] FIG. 1 is a perspective view schematically showing a magnetic memory device according to embodiments of the present invention. Figure 2 is a cross-sectional view of a magnetic memory device along the line A-A' of Figure 1. FIGS. 3a and FIGS. 3b are plan views schematically illustrating a magnetic memory device according to a comparative example of the present invention. FIG. 4 is a perspective view schematically showing a magnetic memory device according to another comparative example of the present invention. FIG. 5 is a graph showing the pulse application timing for the first to fourth conductive lines, intended to explain the operation method of a magnetic memory device according to embodiments of the present invention. FIGS. 6a to 6d are plan views for explaining the operation method of a magnetic memory device according to embodiments of the present invention. FIG. 7 is a perspective view schematically showing a magnetic memory device according to another embodiment of the present invention. FIG. 8 is a graph showing the pulse application timing for the first and second conduction lines, intended to explain the operation method of the magnetic memory device of FIG. 7. FIG. 9 is a perspective view schematically showing a magnetic memory device according to another embodiment of the present invention. Specific details for implementing the invention

[0011] FIG. 1 is a perspective view schematically showing a magnetic memory device according to embodiments of the present invention. FIG. 2 is a cross-sectional view of the magnetic memory device along line A-A' of FIG. 1.

[0012] Referring to FIGS. 1 and 2, a magnetic memory device may include a magnetic track (MTR), a plurality of conductive lines (CL1-CL4) on the magnetic track (MTR), and at least one read / write means (RWE) on the magnetic track (MTR). The magnetic track (MTR) according to embodiments of the present invention may have a loop type or a ring type shape.

[0013] FIGS. 3a and 3b are schematic plan views illustrating a magnetic memory device according to a comparative example of the present invention. Referring to FIGS. 3a and 3b, a magnetic track (MTR') according to a comparative example of the present invention may have a line shape including two ends (ES1, ES2). The magnetic track (MTR') may extend in a first direction (D1). The two ends (ES1, ES2) may include a first end (ES1) and a second end (ES2) facing each other in the first direction (D1).

[0014] The magnetic track (MTR') may include empty regions (BLR) and magnetic domains (MDOs) containing data. As shown in FIGS. 3a and 3b, the magnetic domains (MDOs) may travel back and forth between the two ends (ES1, ES2) of the magnetic track (MTR'). A read / write means (RWE) on the magnetic track (MTR') can read or write data from the magnetic domains (MDOs).

[0015] For all magnetic domains (MDOs) to pass through the read / write means (RWE), the magnetic track (MTR') according to the comparative example must include a blank region (BLR) that occupies half of it. In the present invention, the "blank region (BLR)" may be an area within the magnetic track that does not have a magnetization direction, i.e., does not contain data. In the magnetic track (MTR') according to the comparative example, the data storage area (i.e., magnetic domains (MDOs)) is limited to only half of it due to the blank region (BLR). The magnetic track (MTR') according to the comparative example has a problem of very low data density.

[0016] FIGS. 6a to 6e are schematic plan views illustrating a magnetic memory device according to an embodiment of the present invention. Referring to FIGS. 6a to 6e, the magnetic track (MTR) according to the present invention may be of a loop type with both ends connected to each other. Magnetic domains (MDOs) within the magnetic track (MTR) may circulate along the magnetic track (MTR), and accordingly, a read / write means may read or write data of the magnetic domains (MDOs). FIGS. 6a to 6e illustrate the process of the magnetic domains (MDOs) moving (or circulating) in a clockwise direction. An explanation of the principle of movement of the magnetic domains (MDOs) shown in FIGS. 6a to 6e will be provided later.

[0017] Unlike the magnetic track (MTR') of the comparative example described above, the magnetic track (MTR) according to the present embodiment may not have magnetic domains (MDOs) that reciprocate between the two ends of the track. In the magnetic track (MTR) according to the present embodiment, the magnetic domains (MDOs) may circulate along a loop track. Therefore, unlike the magnetic track (MTR') of the comparative example, the loop-type magnetic track (MTR) according to the present invention may require almost no empty region (BLR). For example, the ratio of the empty region (BLR) within the magnetic track (MTR) may be 0% to 10%. Consequently, the magnetic memory device of the present invention may have an improved data density.

[0018] Referring again to FIGS. 1 and 2, the magnetic track (MTR) according to the present embodiment may include a first part (PA1) and a third part (PA3) that extend parallel to each other in a second direction (D2). The magnetic track (MTR) may further include a second part (PA2) and a fourth part (PA4) that extend parallel to each other in a first direction (D1). The second part (PA2) may connect one end of the first part (PA1) and one end of the third part (PA3) to each other. The fourth part (PA4) may connect the other end of the first part (PA1) and the other end of the third part (PA3) to each other. The first to fourth parts (PA1-PA4) may be arranged sequentially in a counterclockwise direction. By connecting the first to fourth parts (PA1-PA4) to each other, a loop-type magnetic track (MTR) according to the present invention may be provided.

[0019] In the present embodiment, each of the first to fourth parts (PA1-PA4) may have a line shape, thereby providing a rectangular loop-shaped magnetic track (MTR). However, the embodiments of the present invention are not limited thereto. At least one of the first to fourth parts (PA1-PA4) may have a curved shape. Thus, an elliptical or circular magnetic track (MTR) may be provided.

[0020] First to fourth conductive lines (CL1-CL4) may be provided on the magnetic track (MTR). The first and third conductive lines (CL1, CL3) may be extended parallel to each other in a second direction (D2). The second and fourth conductive lines (CL2, CL4) may be extended parallel to each other in a first direction (D1). Specifically, the first to fourth conductive lines (CL1-CL4) may be provided on the first to fourth parts (PA1-PA4) of the magnetic track (MTR), respectively. The first to fourth conductive lines (CL1-CL4) may be provided sequentially on the magnetic track (MTR) along a counterclockwise direction.

[0021] According to embodiments of the present invention, first to fourth conductive lines (CL1-CL4) may be alternately provided on the upper surface (TS) or lower surface (BS) of the magnetic track (MTR). For example, the first conductive line (CL1) may be provided on the upper surface (TS) of the first part (PA1) of the magnetic track (MTR). The second conductive line (CL2) may be provided on the lower surface (BS) of the second part (PA2) of the magnetic track (MTR). The third conductive line (CL3) may be provided on the upper surface (TS) of the third part (PA3) of the magnetic track (MTR). The fourth conductive line (CL4) may be provided on the lower surface (BS) of the second part (PA2) of the magnetic track (MTR). In one embodiment of the present invention, a read / write means (RWE) may be disposed on the upper surface of the second part (PA2) of the magnetic track (MTR).

[0022] Hereinafter, each of the first to fourth conduction lines (CL1-CL4) will be referred to as the conduction line (CL) for description. The conduction line (CL) may be configured to generate spin-orbit torque (SOT) by a current flowing within it. The conduction line (CL) may include a material capable of generating a spin Hall effect or a Rashba effect by a current flowing in its extension direction. The conduction line (CL) may include a heavy metal having an atomic number of 30 or more. For example, the conduction line (CL) may include at least one of iridium (Ir), ruthenium (Ru), tantalum (Ta), platinum (Pt), palladium (Pd), bismuth (Bi), titanium (Ti), and tungsten (W).

[0023] The magnetic track (MTR) may include a lower magnetic layer (LML), a first spacer layer (SPL1), and an upper magnetic layer (UML) stacked in sequence. The lower magnetic layer (LML), the first spacer layer (SPL1), and the upper magnetic layer (UML) may be stacked along a third direction (D3). The first spacer layer (SPL1) may be interposed between the lower magnetic layer (LML) and the upper magnetic layer (UML). For example, each of the lower magnetic layer (LML), the first spacer layer (SPL1), and the upper magnetic layer (UML) may have the same loop shape as the magnetic track (MTR).

[0024] The lower magnetic layer (LML) may include lower magnetic domains (D_L) arranged along a clockwise or counterclockwise direction. The lower magnetic layer (LML) may further include lower magnetic domain walls (DW_L) between the lower magnetic domains (D_L). For example, each lower magnetic domain (D_L) may be a region within the lower magnetic layer (LML) where magnetic moments are aligned in a certain direction. Each lower magnetic domain wall (DW_L) may be a region where the direction of the magnetic moment changes between the lower magnetic domains (D_L). The lower magnetic domains (D_L) and lower magnetic domain walls (DW_L) may be arranged alternately along a clockwise or counterclockwise direction.

[0025] The upper magnetic layer (UML) may include upper magnetic domains (D_U) arranged along a clockwise or counterclockwise direction. The upper magnetic layer (UML) may further include upper magnetic domain walls (DW_U) between the upper magnetic domains (D_U). For example, each upper magnetic domain (D_U) may be a region within the upper magnetic layer (UML) where magnetic moments are aligned in a certain direction. Each upper magnetic domain wall (DW_U) may be a region where the direction of the magnetic moment changes between the upper magnetic domains (D_U). The upper magnetic domains (D_U) and upper magnetic domain walls (DW_U) may be arranged alternately along a clockwise or counterclockwise direction.

[0026] The upper magnetic domains (D_U) can each vertically overlap with the lower magnetic domains (D_L). For example, the lower magnetic domain (D_L) and the upper magnetic domain (D_U) that overlap each other can form a set of magnetic domains (MDO). Each magnetic domain (MDO) can form the free layer of the magnetic tunnel junction (MTJ) described later.

[0027] The lower magnetic layer (LML) and the upper magnetic layer (UML) can be antiferromagnetically coupled to each other through the first spacer layer (SPL1). Each of the lower magnetic layer (LML) and the upper magnetic layer (UML) may contain a magnetic element, and may include at least one of cobalt (Co), iron (Fe), and nickel (Ni), for example. The first spacer layer (SPL1) may contain a non-magnetic metal, and may include ruthenium (Ru), iridium (Ir), tungsten (W), tantalum (Ta), or an alloy thereof, for example.

[0028] In one embodiment, the lower magnetic layer (LML) and the upper magnetic layer (UML) may each comprise at least one of cobalt (Co), iron (Fe), and nickel (Ni), and may further comprise at least one of non-magnetic materials such as boron (B), zinc (Zn), aluminum (Al), titanium (Ti), ruthenium (Ru), tantalum (Ta), silicon (Si), silver (Ag), gold (Au), copper (Cu), carbon (C), and nitrogen (N). In one example, the lower magnetic layer (LML) and the upper magnetic layer (UML) may each comprise at least one of i) a vertical magnetic material (e.g., CoFeTb, CoFeGd, CoFeDy), ii) a vertical magnetic material having an L10 structure, iii) CoPt having a hexagonal close-packed lattice structure, and iv) a vertical magnetic structure. A vertical magnetic material having an L10 structure may include at least one of an L10 structured FePt, an L10 structured FePd, an L10 structured CoPd, or an L10 structured CoPt. The vertical magnetic structure may include alternating and repeatably stacked magnetic layers and non-magnetic layers. As an example, the vertical magnetic structure may include at least one of (Co / Pt)n, (CoFe / Pt)n, (CoFe / Pd)n, (Co / Pd)n, (Co / Ni)n, (CoNi / Pt)n, (CoCr / Pt)n, or (CoCr / Pd)n (where n is the number of stacking layers). The lower magnetic layer (LML) and the upper magnetic layer (UML) may each include CoFeB or a Co-based Heusler alloy.

[0029] At least one read / write means (RWE) may be disposed on the magnetic track (MTR). The read / write means (RWE) may include a GMR sensor utilizing a giant magnetoresistance effect or a TMR sensor utilizing a tunnel magnetoresistance effect. The read / write means (RWE) may be vertically superimposed on any one of the magnetic domains (MDO) within the magnetic track (MTR). As an example, the read / write means (RWE) may include a tunnel barrier pattern (TBP), a first magnetic pattern (MGP1), a second spacer layer (SPL2), a second magnetic pattern (MGP2), and an electrode pattern (TEL) sequentially stacked on the magnetic track (MTR).

[0030] A tunnel barrier pattern (TBP) may be interposed between a first magnetic pattern (MGP1) and an upper magnetic layer (UML). The tunnel barrier pattern (TBP) may include at least one of magnesium (Mg) oxide, titanium (Ti) oxide, aluminum (Al) oxide, magnesium-zinc (Mg-Zn) oxide, or magnesium-boron (Mg-B) oxide.

[0031] The first magnetic pattern (MGP1) may be disposed between the tunnel barrier pattern (TBP) and the second spacer layer (SPL2). The first magnetic pattern (MGP1) may include at least one of cobalt (Co), iron (Fe), and nickel (Ni). More specifically, the first magnetic pattern (MGP1) may include at least one vertical magnetic material among CoFeB, FeB, CoFeBTa, CoHf, Co, and CoZr. For example, the first magnetic pattern (MGP1) may include a single CoFeB film. As another example, the first magnetic pattern (MGP1) may be a multilayer structure including an FeB film and a CoFeB film, a multilayer structure including a Co film and a CoHf film, or a multilayer structure including a CoFeBTa film and a CoFeB film.

[0032] A second spacer layer (SPL2) may be interposed between a first magnetic pattern (MGP1) and a second magnetic pattern (MGP2). The second spacer layer (SPL2) may combine the magnetization direction (MD_PL) of the first magnetic pattern (MGP1) and the magnetization direction (MD_PU) of the second magnetic pattern (MGP2) so as to be antiparallel to each other. For example, the second spacer layer (SPL2) may combine the magnetization directions (MD_PL, MD_PU) of the first and second magnetic patterns (MGP1, MGP2) so as to be antiparallel to each other by means of the RKKY interaction (Ruderman-Kittel-Kasuya-Yosida interaction). Thus, the magnetic fields generated by the magnetization directions (MD_PL, MD_PU) of the first and second magnetic patterns (MGP1, MGP2) cancel each other out, so that the net magnetic field of the read / write means (RWE) can be minimized. As a result, the influence of the magnetic field generated by the read / write means (RWE) on the magnetic track (MTR) can be minimized. The second spacer layer (SPL2) may include at least one of ruthenium (Ru), iridium (Ir), tungsten (W), tantalum (Ta), and rhodium (Rh).

[0033] The second magnetic pattern (MGP2) may include a perpendicular magnetic material. As an example, the second magnetic pattern (MGP2) may include a) cobalt-iron-terbium (CoFeTb) with a terbium (Tb) content ratio of 10% or more, b) cobalt-iron-gadolinium (CoFeGd) with a gadolinium (Gd) content ratio of 10% or more, c) cobalt-iron-dysprosium (CoFeDy), d) FePt with an L10 structure, e) FePd with an L10 structure, f) CoPd with an L10 structure, g) CoPt with an L10 structure, h) CoPt with a close-packed hexagonal lattice structure, and i) an alloy composed of at least one of the materials described above in a) to h). As another example, the second magnetic pattern (MGP2) may be a structure in which magnetic layers and non-magnetic layers are alternately and repeatedly stacked. The structure in which the above magnetic layers and non-magnetic layers are alternately and repeatedly stacked may include a structure of (Co / Pt)n, (CoFe / Pt)n, (CoFe / Pd)n, (Co / Pd)n, (Co / Ni)n, (CoNi / Pt)n, (CoCr / Pt)n, or (CoCr / Pd)n (where n is the number of stacking layers).

[0034] Each of the first and second magnetic patterns (MGP1, MGP2) may have a fixed magnetization direction (MD_PL, MD_PU). Specifically, the magnetization direction (MD_PL, MD_PU) of each of the first and second magnetic patterns (MGP1, MGP2) may be substantially perpendicular to one side of the first magnetic pattern (MGP1) that contacts the tunnel barrier pattern (TBP) (e.g., the bottom surface of the first magnetic pattern (MGP1)). The magnetization direction (MD_PL) of the first magnetic pattern (MGP1) may be fixed antiparallel to the magnetization direction (MD_PU) of the second magnetic pattern (MGP2) by the second spacer layer (SPL2).

[0035] According to another embodiment of the present invention, the second magnetic pattern (MGP2) and the second spacer layer (SPL2) may be omitted. That is, the bottom surface of the first magnetic pattern (MGP1) may be in contact with the tunnel barrier pattern (TBP), and the top surface of the first magnetic pattern (MGP1) may be in contact with the electrode pattern (TEL).

[0036] The electrode pattern (TEL) may include a conductive material. For example, the electrode pattern (TEL) may include a metal (for example, copper, tungsten, or aluminum) and / or a metal nitride (for example, tantalum nitride, titanium nitride, or tungsten nitride).

[0037] The lower magnetic domains (D_L) within the lower magnetic layer (LML) and the upper magnetic domains (D_U) within the upper magnetic layer (UML) may have perpendicular magnetic anisotropy (PMA). Each of the lower magnetic domains (D_L) within the lower magnetic layer (LML) may have a magnetization direction (MD_L) perpendicular to the interface between the lower magnetic layer (LML) and the first spacer layer (SPL1). The magnetization direction (MD_L) of each lower magnetic domain (D_L) may be parallel to the third direction (D3). The magnetization directions (MD_L) of adjacent lower magnetic domains (D_L) may be parallel or antiparallel to each other. A lower magnetic domain wall (DW_L) may be defined between adjacent lower magnetic domains (D_L).

[0038] Each of the upper magnetic domains (D_U) within the upper magnetic layer (UML) may have a magnetization direction (MD_U) perpendicular to the interface between the upper magnetic layer (UML) and the first spacer layer (SPL1). The magnetization directions (MD_L) of adjacent upper magnetic domains (D_U) may be parallel or antiparallel to each other. An upper magnetic domain wall (DW_U) may be defined between adjacent upper magnetic domains (D_U).

[0039] The upper magnetic domains (D_U) can be vertically superimposed with the lower magnetic domains (D_L), respectively. The upper magnetic domains (D_U) and lower magnetic domains (D_L) that overlap each other can be antiferromagnetically coupled to each other through the first spacer layer (SPL1). The magnetization direction (MD_U) of the upper magnetic domain (D_U) can be antiparallel to the magnetization direction (MD_L) of the corresponding lower magnetic domain (D_L).

[0040] Referring again to FIG. 2, when the current (CUR) flows in the first direction (D1) within the second conductive line (CL2), the lower magnetic domains (D_L) may move in the first direction (D1) or in the opposite direction of the first direction (D1). It can be observed that the lower magnetic domains (D_L) move relatively due to the movement of the lower magnetic domain walls (DW_L) caused by the current (CUR). The lower magnetic domains (D_L) on the second conductive line (CL2) may move in a direction parallel or antiparallel to the current (CUR). In one embodiment, the lower magnetic domains (D_L) on the second conductive line (CL2) may move in the first direction (D1) parallel to the current (CUR).

[0041] The movement of the lower domains (D_L) (or the movement of the lower domain walls (DW_L)) can be attributed to spin-orbit torque and Dzyaloshinskii-Moriya interaction (DMI) occurring at the interface between the second conduction line (CL2) and the lower magnetic layer (LML). The direction of movement of the lower domain walls (DW_L) may depend on the chirality of the lower domain walls (DW_L).

[0042] As the lower domain walls (DW_L) within the lower magnetic layer (LML) move in the first direction (D1), the upper domain walls (DW_U) within the upper magnetic layer (UML) may also move in the first direction (D1). The movement of the upper domain walls (DW_U) may be attributed to the antiferromagnetic coupling between the lower magnetic layer (LML) and the upper magnetic layer (UML). Alternatively, as the lower domains (D_L) within the lower magnetic layer (LML) move in the first direction (D1), the upper domains (D_U) within the upper magnetic layer (UML) may also move in the first direction (D1).

[0043] The first magnetic pattern (MGP1) of the read / write means (RWE) may have perpendicular magnetic anisotropy (PMA). The first magnetic pattern (MGP1) may have a magnetization direction (MD_PL) perpendicular to the interface between the first magnetic pattern (MGP1) and the tunnel barrier pattern (TBP). The magnetization direction (MD_PL) of the first magnetic pattern (MGP1) may be fixed.

[0044] The first and second magnetic patterns (MGP1, MGP2) may be vertically superimposed with any one magnetic domain (MDO) within the magnetic track (MTR). The first and second magnetic patterns (MGP1, MGP2) and the magnetic domain (MDO) beneath them may form a magnetic tunnel junction (MTJ). The first and second magnetic patterns (MGP1, MGP2) may be a fixed layer having fixed magnetization directions (MD_PL, MD_PU). The corresponding upper magnetic domain (D_U) and the corresponding lower magnetic domain (D_L) may be antiferromagnetically coupled to each other to form a free layer of a composite antiferromagnetic structure.

[0045] When a read operation is performed by the read / write means (RWE), a read current (Iread) may flow through the magnetic tunnel junction (MTJ). The resistance state of the magnetic tunnel junction (MTJ) may be detected by the read current (Iread). Whether the magnetic tunnel junction (MTJ) is in a high resistance state or a low resistance state may be detected by the read current (Iread). Data (0 or 1) stored within the magnetic domain (MDO) may be detected from the resistance state of the magnetic tunnel junction (MTJ). In other words, each magnetic domain (MDO) within the magnetic track (MTR) may correspond to one bit.

[0046] During a write operation of the read / write means (RWE), a write current (Isw) may flow through the magnetic tunnel junction (MTJ). The magnitude of the write current (Isw) may be greater than the magnitude of the read current (Iread). The magnetization direction (MD_U) of the corresponding upper magnetic domain (D_U) may be switched by the spin transfer torque generated by the write current (Isw). The magnetization direction (MD_L) of the lower magnetic domain (D_L) that is antiferromagnetically coupled to the upper magnetic domain (D_U) may be switched to be antiparallel to the magnetization direction (MD_U) of the upper magnetic domain (D_U).

[0047] Referring again to FIGS. 1 and FIGS. 2, the first to fourth conductive lines (CL1-CL4) can be arranged alternately on the upper surface (TS) or the lower surface (BS) of the magnetic track (MTR). This allows current to flow through the first to fourth conductive lines (CL1-CL4) over the entire area of ​​the magnetic track (MTR), i.e., the first to fourth parts (PA1-PA4).

[0048] Typically, the second conductive line (CL2) may include a first end portion (ENP1) and a second end portion (ENP2) adjacent to each of its ends. The first end portion (ENP1) and the second end portion (ENP2) may face each other in a first direction (D1). A first contact (CNT1) may be electrically connected to the first end portion (ENP1). A second contact (CNT2) may be electrically connected to the second end portion (ENP2).

[0049] A first voltage can be applied to a first end portion (ENP1) through a first contact (CNT1), and a second voltage can be applied to a second end portion (ENP2) through a second contact (CNT2). For example, the first voltage may be Vp having a positive value, and the second voltage may be a ground voltage of 0 V. By applying voltages of Vp and 0 V to each end of the second conductive line (CL2), a voltage difference may occur between the two ends of the second conductive line (CL2). As a result, current (CUR) may flow in a first direction (D1) within the second conductive line (CL2).

[0050] Referring to FIG. 1, a first voltage through a first contact (CNT1) and a second voltage through a second contact (CNT2) can be applied to each end of the first conductive line (CL1). This allows current (CUR) to flow in the first conductive line (CL1) in the opposite direction of the second direction (D2). A first voltage through a first contact (CNT1) and a second voltage through a second contact (CNT2) can be applied to each end of the third conductive line (CL3). This allows current (CUR) to flow in the second direction (D2) through the third conductive line (CL3). A first voltage through a first contact (CNT1) and a second voltage through a second contact (CNT2) can be applied to each end of the fourth conductive line (CL4). Thus, current (CUR) can flow in the fourth challenge line (CL4) in the opposite direction to the first direction (D1).

[0051] In this embodiment, the ends of adjacent conductive lines among the first to fourth conductive lines (CL1-CL4) may overlap vertically with each other. Specifically, referring to FIG. 2, the first end (ENP1) of the second conductive line (CL2) may overlap vertically with the end of the third conductive line (CL3) above it. The second end (ENP2) of the second conductive line (CL2) may overlap vertically with the end of the first conductive line (CL1) above it.

[0052] FIG. 4 is a perspective view schematically illustrating a magnetic memory device according to another comparative example of the present invention. Referring to FIG. 4, the magnetic memory device according to the comparative example may include a single conductive line (CL). The conductive line (CL) may be provided below a magnetic track (MTR). The conductive line (CL) may have a loop shape similar to the magnetic track (MTR). However, the two ends (EN1, EN2) of the conductive line (CL) may be spaced apart and not connected to each other.

[0053] Specifically, the first terminal (EN1) and the second terminal (EN2) of the conductive line (CL) may be adjacent to each other but separated. A first voltage through the first contact (CNT1) may be applied to the first terminal (EN1) of the conductive line (CL), and a second voltage through the second contact (CNT2) may be applied to the second terminal (EN2) of the conductive line (CL). This allows current (CUR) to flow counterclockwise within the conductive line (CL). To generate a voltage difference that allows current (CUR) to flow in a loop-shaped conductive line (CL), the two terminals (EN1, EN2) of the conductive line (CL) must be separated, and a first voltage and a second voltage must be applied to them, respectively.

[0054] Meanwhile, in the magnetic memory device according to the comparative example, the two ends (EN1, EN2) of the conductive line (CL) are separated, so a spin-orbit torque (SOT) gap (Lgap) occurs between them. The SOT gap (Lgap) causes a problem that significantly changes the movement speed of the magnetic domain (or domain wall). Furthermore, a constraint arises that a considerably large dielectric thickness is required between the two ends (EN1, EN2) of the conductive line (CL) to withstand the voltage difference between them. As the SOT gap (Lgap) increases, there is a problem that the magnetic memory device malfunctions and its reliability deteriorates.

[0055] Referring again to FIGS. 1 and 2, the magnetic memory device according to the present invention can separate the first to fourth conductive lines (CL1-CL4) from each other and alternately arrange them up and down on a magnetic track (MTR). By doing so, a voltage difference can be generated in each of the first to fourth conductive lines (CL1-CL4) to cause current (CUR) to flow in each of the first to fourth conductive lines (CL1-CL4).

[0056] The first to fourth conductive lines (CL1-CL4) can cover the entire area of ​​the magnetic track (MTR), that is, the first to fourth parts (PA1-PA4), respectively. In particular, the conductive lines among the first to fourth conductive lines (CL1-CL4) of the present invention that are adjacent to each other are arranged so that their ends overlap perpendicularly, thereby covering the entire area of ​​the magnetic track (MTR) without omission. The present invention does not cause an SOT gap (Lgap) as shown in FIG. 4, thereby allowing the movement speed of the magnetic domain (MDO) to be controlled consistently and preventing malfunction of the device.

[0058] FIG. 5 is a graph showing the pulse application timing for the first to fourth conductive lines, for explaining the operation method of a magnetic memory device according to embodiments of the present invention. FIGS. 6a to 6d are plan views for explaining the operation method of a magnetic memory device according to embodiments of the present invention.

[0059] Referring to FIG. 6a, a magnetic track (MTR) according to one embodiment of the present invention may be provided. The magnetic track (MTR) of this embodiment may be substantially the same as the magnetic track (MTR) of the magnetic memory device described above with reference to FIG. 1 and FIG. 2. The magnetic track (MTR) may include first to fourth parts (PA1-PA4). The first to fourth parts (PA1-PA4) may be connected to each other so that the magnetic track (MTR) may have a loop shape.

[0060] First to fourth conductive lines (CL1-CL4) may be provided on the first to fourth portions (PA1-PA4) of the magnetic track (MTR), respectively. As previously described with reference to FIGS. 1 and 2, the first to fourth conductive lines (CL1-CL4) may be arranged alternately on the upper or lower surface of the magnetic track (MTR). The first and third conductive lines (CL1, CL3) may be provided on the upper surface of the magnetic track (MTR), and the second and fourth conductive lines (CL2, CL4) may be provided on the lower surface of the magnetic track (MTR).

[0061] The magnetic track (MTR) may include multiple magnetic domains (MDOs). A magnetic domain wall (DW) may be provided between adjacent magnetic domains (MDOs). Any one of the multiple magnetic domains (MDOs) may be defined as the target magnetic domain (MDO_T) of this embodiment. A star mark is indicated on the target magnetic domain (MDO_T) to distinguish it from other magnetic domains (MDOs). The magnetic track (MTR) may include at least one empty region (BLR). For example, the empty region (BLR) may be located at the point where the first part (PA1) and the fourth part (PA4) meet.

[0062] Referring to FIGS. 5 and FIGS. 6b, a pulse (or voltage) is applied to the first conductive line (CL1) in the first step (S1) so that a current (CUR) may flow within the first conductive line (CL1). The current (CUR) within the first conductive line (CL1) may flow in the opposite direction of the second direction (D2). The current (CUR) within the first conductive line (CL1) may flow in a counterclockwise direction.

[0063] Magnetic domains (MDO) in the first part (PA1) can move in the second direction (D2) by the current (CUR) in the first conductive line (CL1). Magnetic domains (MDO) in the first part (PA1) can move in a clockwise direction. The direction of magnetic domain movement (DOR) of the first part (PA1) can be clockwise. The first conductive line (CL1) is provided on the upper surface of the magnetic track (MTR), thereby allowing the direction of magnetic domain movement (DOR) of the first part (PA1) to be opposite to the direction of the current (CUR).

[0064] The target magnetic domain (MDO_T) can occupy the empty region (BLR) by moving clockwise due to the current (CUR). As the magnetic domains (MDO) within the first part (PA1) move clockwise in unison, a new empty region (BLR) can be formed at the point where the first part (PA1) and the second part (PA2) meet.

[0065] Referring to FIG. 5 and FIG. 6c, a pulse is applied to the second conductive line (CL2) in the second step (S2) so that a current (CUR) can flow within the second conductive line (CL2). The current (CUR) within the second conductive line (CL2) can flow in the first direction (D1). The current (CUR) within the second conductive line (CL2) can flow in the clockwise direction. The direction of the current within the second conductive line (CL2) (e.g., clockwise) may be opposite to the direction of the current within the first conductive line (CL1) described above (e.g., counterclockwise).

[0066] The magnetic domains (MDO) in the second part (PA2) can move in the first direction (D1) (or clockwise) by the current (CUR) in the second conduction line (CL2). The magnetic domains (MDO) in the second part (PA2) can move clockwise. The direction of magnetic domain movement (DOR) of the second part (PA2) may be the same clockwise direction as the direction of magnetic domain movement (DOR) of the first part (PA1) described above. The second conduction line (CL2) is provided on the bottom surface of the magnetic track (MTR), so that the direction of magnetic domain movement (DOR) of the second part (PA2) may be the same as the direction of the current (CUR).

[0067] As the magnetic domains (MDO) within the second part (PA2) move in a clockwise direction in unison, a new empty region (BLR) can be formed at the point where the second part (PA2) and the third part (PA3) meet. Meanwhile, in the second step (S2), the target magnetic domain (MDO_T) can be fixed without moving.

[0068] Referring to FIGS. 5 and FIGS. 6d, a pulse is applied to the third conductive line (CL3) in the third step (S3) so that a current (CUR) may flow within the third conductive line (CL3). The current (CUR) within the third conductive line (CL3) may flow in a counterclockwise direction. The direction of the current within the third conductive line (CL3) (e.g., counterclockwise) may be opposite to the direction of the current within the second conductive line (CL2) described above (e.g., clockwise).

[0069] The magnetic domains (MDO) in the third part (PA3) can move clockwise by the current (CUR) in the third conduction line (CL3). The direction of magnetic domain movement (DOR) in the third part (PA3) may be the same clockwise direction as the direction of magnetic domain movement (DOR) in the second part (PA2) described above. The third conduction line (CL3) is provided on the upper surface of the magnetic track (MTR), thereby allowing the direction of magnetic domain movement (DOR) in the third part (PA3) to be opposite to the direction of the current (CUR).

[0070] As the magnetic domains (MDO) within the third part (PA3) move in a clockwise direction in unison, a new empty region (BLR) can be formed at the point where the third part (PA3) and the fourth part (PA4) meet. Meanwhile, in the third step (S3), the target magnetic domain (MDO_T) can be fixed without moving.

[0071] Referring to FIGS. 5 and 6e, a pulse is applied to the fourth conductive line (CL4) in the fourth step (S4) so ​​that a current (CUR) may flow within the fourth conductive line (CL4). The current (CUR) within the fourth conductive line (CL4) may flow in a clockwise direction. The direction of the current within the fourth conductive line (CL4) (e.g., clockwise) may be opposite to the direction of the current within the third conductive line (CL3) described above (e.g., counterclockwise).

[0072] The magnetic domains (MDO) in the fourth part (PA4) can move clockwise by the current (CUR) in the fourth conduction line (CL4). The direction of magnetic domain movement (DOR) in the fourth part (PA4) may be the same clockwise direction as the direction of magnetic domain movement (DOR) in the third part (PA3) described above. The fourth conduction line (CL4) is provided on the bottom surface of the magnetic track (MTR), so that the direction of magnetic domain movement (DOR) in the fourth part (PA4) may be the same as the direction of the current (CUR).

[0073] The target magnetic domain (MDO_T) can move clockwise by the current (CUR). As the magnetic domains (MDO) within the fourth part (PA4) move clockwise in unison, an empty region (BLR) can be formed again at the point where the fourth part (PA4) and the first part (PA1) meet.

[0074] Referring again to FIGS. 5 and FIGS. 6a through 6e, magnetic domains (MDOs) can be moved by applying pulses to the first through fourth conduction lines (CL1-CL4) sequentially rather than simultaneously. For example, a target magnetic domain (MDO_T) moved clockwise from the first part (PA1) to the fourth part (PA4) by going through the first through fourth steps (S1-S4). By repeating the first through fourth steps (S1-S4) of FIG. 5, magnetic domains (MDOs) within the magnetic track (MTR) can be moved (or circulated) clockwise continuously. The magnetic memory device according to the present embodiment can read or write data while moving the magnetic domains (MDOs) in the manner described above.

[0075] In a magnetic memory device using spin-orbit torque according to embodiments of the present invention, the direction of current and the direction of magnetic domain movement may be parallel or antiparallel to each other as the conductive lines (CL1-CL4) are located on the upper or lower surface of the magnetic track (MTR).

[0076] For example, as shown in FIG. 6b, when a current (CUR) flows in a counterclockwise direction in a first conductive line (CL1) located on the upper surface of a magnetic track (MTR), the direction of magnetic domain movement (DOR) may be clockwise. That is, the direction of the current (CUR) on the first conductive line (CL1) and the direction of magnetic domain movement (DOR) may be antiparallel (or opposite) to each other.

[0077] As shown in FIG. 6c, when a current (CUR) flows clockwise in a second conductive line (CL2) located on the bottom surface of a magnetic track (MTR), the direction of magnetic domain movement (DOR) may be clockwise. That is, the direction of the current (CUR) on the second conductive line (CL2) and the direction of magnetic domain movement (DOR) may be parallel (or identical) to each other. Consequently, the first to fourth conductive lines (CL1-CL4) according to the present invention may be configured so that a current (CUR) flows alternately clockwise or counterclockwise to circulate the magnetic domains (MDO).

[0079] FIG. 7 is a schematic perspective view of a magnetic memory device according to another embodiment of the present invention. FIG. 8 is a graph showing the pulse application timing for the first and second conductive lines, intended to explain the operation method of the magnetic memory device of FIG. 7. In this embodiment, detailed descriptions of technical features that overlap with those previously described with reference to FIG. 1 and FIG. 2 are omitted, and differences are described in detail.

[0080] Referring to FIG. 7, a first conductive line (CL1) and a second conductive line (CL2) may be provided on a magnetic track (MTR). The first conductive line (CL1) may be provided on the first and fourth parts (PA1, PA4) of the magnetic track (MTR). The first conductive line (CL1) may be provided on the upper surfaces of the first and fourth parts (PA1, PA4). The first conductive line (CL1) may include a region extending in a second direction (D2) on the first part (PA1) and a region extending in a first direction (D1) on the fourth part (PA4). In other words, the first conductive line (CL1) may have an L-shape.

[0081] A second conductive line (CL2) may be provided on the second and third parts (PA2, PA3) of the magnetic track (MTR). The second conductive line (CL2) may be provided on the bottom surfaces of the second and third parts (PA2, PA3). The second conductive line (CL2) may include a region extending in a first direction (D1) on the second part (PA2) and a region extending in a second direction (D2) on the third part (PA3). In other words, the second conductive line (CL2) may have an L-shape.

[0082] The first end portion (ENP1) of the first conductive line (CL1) and the first end portion (ENP1) of the second conductive line (CL2) can be vertically overlapped with each other. A first voltage (Vp) can be applied to the first end portion (ENP1) of the first conductive line (CL1) and the first end portion (ENP1) of the second conductive line (CL2) through a first contact (CNT1).

[0083] The second end portion (ENP2) of the first conduction line (CL1) and the second end portion (ENP2) of the second conduction line (CL2) can be vertically overlapped with each other. A second voltage (0 V) can be applied to the second end portion (ENP2) of the first conduction line (CL1) and the second end portion (ENP2) of the second conduction line (CL2) through a second contact (CNT2).

[0084] Referring to FIGS. 7 and 8, the movement of magnetic domains (MDOs) within a magnetic memory device according to the present embodiment may include sequentially applying pulses to a first conductive line (CL1) and a second conductive line (CL2). When pulses are repeatedly applied alternately to the first conductive line (CL1) and the second conductive line (CL2), the magnetic domains (MDOs) may move clockwise along a magnetic track (MTR), as previously described with reference to FIGS. 6a to 6e.

[0086] FIG. 9 is a schematic perspective view of a magnetic memory device according to another embodiment of the present invention. In this embodiment, detailed descriptions of technical features that overlap with those previously described with reference to FIG. 1 and FIG. 2 are omitted, and differences are described in detail.

[0087] Referring to FIG. 9, magnetic insulators (MIN) may be provided within a magnetic track (MTR). The magnetic insulators (MIN) may be placed at the corners of the magnetic track (MTR). For example, the magnetic insulators (MIN) in the second part (PA2) of the magnetic track (MTR) may be placed adjacent to the first conductive line (CL1) and the third conductive line (CL3), respectively.

[0088] Leakage current (LKC) may occur through the second part (PA2) of the magnetic track (MTR) between the first and third conduction lines (CL1, CL3). The magnetic insulators (MIN) according to the present embodiment can be placed between the first and third conduction lines (CL1, CL3) to prevent leakage current (LKC). This allows the magnetic properties of the magnetic track (MTR) to be maintained while effectively preventing leakage current (LKC), thereby improving the electrical properties of the magnetic memory device.

[0089] Each magnetic insulator (MIN) may include a ferrimagnetic insulator or a ferromagnetic insulator. For example, each magnetic insulator (MIN) may include MgFe2O4, Fe3O4, NiFe2O4Li 0.5 Fe 2.5 It may include at least one of O4, NiFe2O4, and CoFe2O4.

[0091] Although embodiments of the present invention have been described above with reference to the attached drawings, the present invention may be implemented in other specific forms without altering its technical concept or essential features. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

Claim 1 A magnetic memory device comprising a loop-type magnetic track, wherein the magnetic track comprises a first portion and a second portion arranged in a counterclockwise direction; a first conductive line on the upper surface of the first portion; and a second conductive line on the lower surface of the second portion, wherein the magnetic track comprises a lower magnetic layer, a spacer layer, and an upper magnetic layer sequentially stacked, and each of the first and second conductive lines comprises a heavy metal, and each of the first and second conductive lines is configured to generate a spin-orbit torque by a current flowing therein, and magnetic domains within the magnetic track move in a clockwise or counterclockwise direction by the spin-orbit torque. Claim 2 A magnetic memory device according to claim 1, wherein the first conductive line includes a first end portion and a second end portion adjacent to each of its ends, and the second conductive line includes a third end portion and a fourth end portion adjacent to each of its ends, and the first end portion and the third end portion overlap each other perpendicularly. Claim 3 A magnetic memory device according to claim 2, further comprising: a first contact and a second contact electrically connected to the first end portion and the second end portion, respectively; and a third contact and a fourth contact electrically connected to the third end portion and the fourth end portion, respectively, wherein a first voltage is applied to the first contact and the third contact, and a second voltage is applied to the second contact and the fourth contact. Claim 4 A magnetic memory device according to claim 1, wherein the lower magnetic layer and the upper magnetic layer are antiferromagnetically coupled to each other through the spacer layer. Claim 5 A magnetic memory device according to claim 1, wherein the first conductive line is disposed on the upper magnetic layer and the second conductive line is disposed on the lower magnetic layer. Claim 6 A magnetic memory device according to claim 1, wherein the lower magnetic layer comprises a plurality of lower magnetic domains and lower magnetic domain walls between the plurality of lower magnetic domains, and the upper magnetic layer comprises a plurality of upper magnetic domains and upper magnetic domain walls between the plurality of upper magnetic domains, wherein the lower magnetic domains and the upper magnetic domains each overlap vertically with one another to form the magnetic domains. Claim 7 A magnetic memory device according to claim 1, further comprising a read / write means on the magnetic track, wherein the read / write means comprises a tunnel barrier pattern, a magnetic pattern, and an electrode pattern sequentially stacked on the magnetic track, and the magnetic pattern having a fixed magnetization direction. Claim 8 In claim 7, the magnetic track is a magnetic memory device interposed between any one of the first and second conductive lines and the read / write means. Claim 9 A magnetic memory device according to claim 1, further comprising a third conductive line and a fourth conductive line, wherein the magnetic track further comprises a third part and a fourth part, the first to fourth parts are arranged in a counterclockwise direction, the first part and the fourth part are connected to each other, the third conductive line is disposed on the upper surface of the third part, and the fourth conductive line is disposed on the bottom surface of the fourth part. Claim 10 In claim 1, a corner of the magnetic track is defined at the point where the first part and the second part meet, and the magnetic track includes a magnetic insulator adjacent to the corner, and the magnetic insulator is MgFe2O4, Fe3O4, NiFe2O4Li 0.5 Fe 2.5 A magnetic memory device comprising at least one of O4, NiFe2O4, and CoFe2O4. Claim 11 A magnetic memory device comprising a loop-type magnetic track, wherein the magnetic track includes a first portion and a second portion arranged in a counterclockwise direction; a first conductive line on the upper surface of the first portion; and a second conductive line on the lower surface of the second portion, wherein the magnetic track includes a lower magnetic layer, a spacer layer, and an upper magnetic layer sequentially stacked, and each of the first and second conductive lines is configured to generate a spin-orbit torque by a current flowing therein, wherein the first conductive line is configured such that the current flows in a clockwise or counterclockwise direction, and the second conductive line is configured such that the current flows in a counterclockwise or clockwise direction, and the direction of the current of the first conductive line is opposite to the direction of the current of the second conductive line. Claim 12 In claim 11, the magnetic memory device in which the direction of movement of the magnetic domain on the first conductive line is the same as the direction of movement of the magnetic domain on the second conductive line. Claim 13 In claim 11, the first conductive line includes a first end portion and a second end portion adjacent to each of its ends, and the second conductive line includes a third end portion and a fourth end portion adjacent to each of its ends, and the first end portion and the third end portion overlap each other perpendicularly, forming a magnetic memory device. Claim 14 A magnetic memory device according to claim 13, further comprising: a first contact and a second contact electrically connected to the first end portion and the second end portion, respectively; and a third contact and a fourth contact electrically connected to the third end portion and the fourth end portion, respectively, wherein a first voltage is applied to the first contact and the third contact, and a second voltage is applied to the second contact and the fourth contact. Claim 15 A magnetic memory device according to claim 11, further comprising a read / write means on the magnetic track, wherein the read / write means comprises a tunnel barrier pattern, a magnetic pattern, and an electrode pattern sequentially stacked on the magnetic track, and the magnetic pattern having a fixed magnetization direction. Claim 16 A method of operation of a magnetic memory device, wherein the magnetic memory device comprises: a loop-type magnetic track, wherein the magnetic track comprises first to fourth portions arranged in a counterclockwise direction, and the first portion and the fourth portion are connected to each other; a first conductive line on the upper surface of the first portion; a second conductive line on the bottom surface of the second portion; a third conductive line on the upper surface of the third portion; and a fourth conductive line on the bottom surface of the fourth portion, wherein each of the first to fourth conductive lines is configured to generate a spin-orbit torque by a current flowing therein, and the method of operation comprises: a first step of applying a pulse to the first conductive line to move magnetic domains on the first conductive line in a clockwise direction; a second step of applying a pulse to the second conductive line to move magnetic domains on the second conductive line in the clockwise direction; and a third step of applying a pulse to the third conductive line to move magnetic domains on the third conductive line in the clockwise direction. A method of operating a magnetic memory device comprising a fourth step of applying a pulse to the fourth conductive line to move magnetic domains on the fourth conductive line in the clockwise direction, wherein the first to fourth steps are performed sequentially. Claim 17 A method of operation of a magnetic memory device according to claim 16, further comprising repeating the above steps 1 through 4. Claim 18 A method of operation of a magnetic memory device according to claim 16, wherein the pulse is applied to the first and third conductive lines so that the current flows in a clockwise or counterclockwise direction, and the pulse is applied to the second and fourth conductive lines so that the current flows in a counterclockwise or clockwise direction, and the direction of the current in the first and third conductive lines is opposite to the direction of the current in the second and fourth conductive lines. Claim 19 A method of operation of a magnetic memory device according to claim 16, wherein corners of the magnetic track are each defined at points where the first to fourth parts meet each other, and the magnetic track includes magnetic insulators adjacent to each of the corners, and the magnetic insulators are configured to prevent leakage current. Claim 20 A method of operation of a magnetic memory device according to claim 16, wherein the magnetic track includes an empty area at the point where the first part and the fourth part meet each other, and during the first step, at least one magnetic domain on the first conductive line moves clockwise to occupy the empty area.

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