Patent Publication Number: US-2023165164-A1

Title: Magnetic memory device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This U.S. non-provisional patent application claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2021-0164289, filed on Nov. 25, 2021, in the Korean Intellectual Property Office, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     The present disclosure relates to a magnetic memory device, and more particularly, to a magnetic memory device using a movement phenomenon of a magnetic domain wall. 
     Demand has increased for high-speed and low-voltage memory devices for use in high-speed and low-power electronic devices including memory devices. A magnetic memory device has been considered as a candidate memory device that may satisfy these demands. The magnetic memory device has been spotlighted as a next-generation memory device because of its high-speed operation characteristics and/or non-volatile characteristics. In particular, a new magnetic memory device using a movement phenomenon of a magnetic domain wall of a magnetic material has been researched and developed. 
     SUMMARY 
     Embodiments of the inventive concepts may provide a magnetic memory device configured to inject a magnetic domain wall into a magnetic track including a synthetic antiferromagnetic structure. 
     Embodiments of the inventive concepts may also provide a magnetic memory device configured to reduce a current density for injecting a magnetic domain wall into a magnetic track including a synthetic antiferromagnetic structure. 
     In an aspect, a magnetic memory device may include a magnetic track extending in a first direction. The magnetic track may include a lower magnetic layer, an upper magnetic layer on the lower magnetic layer, a non-magnetic pattern on the lower magnetic layer and at a side of the upper magnetic layer, and a spacer layer between the lower magnetic layer and the upper magnetic layer and extending between the lower magnetic layer and the non-magnetic pattern. The lower magnetic layer and the upper magnetic layer may be antiferromagnetically coupled to each other by the spacer layer. The non-magnetic pattern may have a first surface and a second surface which are opposite to each other in a second direction perpendicular to the first direction, and the first direction and the second direction may be parallel to a plane. A junction surface between the non-magnetic pattern and the upper magnetic layer may be inclined with respect to a reference surface perpendicular to the first surface and the second surface of the non-magnetic pattern. 
     In an aspect, a magnetic memory device may include a magnetic track extending in a first direction. The magnetic track may include a lower magnetic layer, an upper magnetic layer on the lower magnetic layer, a non-magnetic pattern on the lower magnetic layer and at a side of the upper magnetic layer, and a spacer layer between the lower magnetic layer and the upper magnetic layer and extending between the lower magnetic layer and the non-magnetic pattern. The lower magnetic layer and the upper magnetic layer may be antiferromagnetically coupled to each other by the spacer layer. The non-magnetic pattern may have a first surface and a second surface which are opposite to each other in a second direction perpendicular to the first direction, and the first direction and the second direction may be parallel to a plane. A length of the non-magnetic pattern in the first direction may become progressively greater from the first surface toward the second surface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a plan view illustrating a magnetic memory device according to some embodiments of the inventive concepts. 
         FIG.  2    is a cross-sectional view illustrating a magnetic memory device according to some embodiments of the inventive concepts. 
         FIGS.  3 A to  6 A  are plan views corresponding to a portion ‘A’ of  FIG.  1    to illustrate a method of manufacturing a magnetic memory device according to some embodiments of the inventive concepts. 
         FIGS.  3 B to  6 B  are cross-sectional views corresponding to a portion ‘B’ of  FIG.  2    to illustrate a method of manufacturing a magnetic memory device according to some embodiments of the inventive concepts. 
         FIGS.  7 A to  7 D  are cross-sectional views corresponding to the portion ‘B’ of  FIG.  2    to illustrate a method for initializing a magnetic memory device according to some embodiments of the inventive concepts. 
         FIGS.  8  and  9    are graphs showing a current density for injecting a magnetic domain wall into a magnetic track of a magnetic memory device according to some embodiments of the inventive concepts. 
         FIG.  10    is a cross-sectional view illustrating a magnetic memory device according to some embodiments of the inventive concepts. 
     
    
    
     DETAILED DESCRIPTION 
     Example embodiments of the inventive concepts will now be described more fully with reference to the accompanying drawings. The present disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In the drawings, like numerals refer to like elements throughout this application and repeated descriptions may be omitted. It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. Thus, for example, a first element, a first component or a first section discussed below could be termed a second element, a second component or a second section without departing from the teachings of the present inventive concept. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It is noted that aspects described with respect to one embodiment may be incorporated in different embodiments although not specifically described relative thereto. That is, all embodiments and/or features of any embodiments can be combined in any way and/or combination. 
       FIG.  1    is a plan view illustrating a magnetic memory device according to some embodiments of the inventive concepts.  FIG.  2    is a cross-sectional view illustrating a magnetic memory device according to some embodiments of the inventive concepts. 
     Referring to  FIGS.  1  and  2   , a magnetic memory device may include a conductive line CL, a magnetic track MTR on the conductive line CL, and a read/write unit  150  on the magnetic track MTR. Each of the conductive line CL and the magnetic track MTR may have a line shape extending in a first direction D 1 . Each of the conductive line CL and the magnetic track MTR may have a line shape in which a length in the first direction D 1  is greater than a width in a second direction D 2  perpendicular to the first direction D 1 . The first direction D 1  and the second direction D 2  may be parallel to a plane (for example, a lower surface of the conductive line CL) and may be perpendicular to each other. In other words, a plane defined by the first direction D 1  and the second direction D 2  may be parallel to a lower surface of the conductive line CL. The magnetic track MTR may be stacked on the conductive line CL in a third direction D 3  perpendicular to both the first direction D 1  and the second direction D 2 . The third direction D 3  may be perpendicular to the plane (for example, the lower surface of the conductive line CL or a plane defined by the first direction D 1  and the second direction D 2 ). The read/write unit  150  may be disposed adjacent to a portion of the magnetic track MTR. 
     The conductive line CL may be configured to generate spin-orbit torque by or in response to a current flowing therethrough. The conductive line CL may include a material configured to generate a spin hall effect or a Rashba effect by or in response to a current flowing in the first direction D 1  or an opposite direction to the first direction D 1  in the conductive line CL. The conductive line CL may include a heavy metal having an atomic number of 30 or more and may include, for example, iridium (Ir), ruthenium (Ru), tantalum (Ta), platinum (Pt), palladium (Pd), bismuth (Bi), titanium (Ti), and/or tungsten (W). 
     The magnetic track MTR may include a lower magnetic layer  110 , a spacer layer  120  and an upper magnetic layer  130 , which are sequentially stacked on the conductive line CL. The lower magnetic layer  110 , the spacer layer  120  and the upper magnetic layer  130  may be sequentially stacked on the conductive line CL in the third direction D 3 . The lower magnetic layer  110  may be disposed between the conductive line CL and the spacer layer  120 , and the spacer layer  120  may be disposed between the lower magnetic layer  110  and the upper magnetic layer  130 . The lower magnetic layer  110 , the spacer layer  120 , and the upper magnetic layer  130  may have line shapes extending in the first direction D 1 . The conductive line CL and the magnetic track MTR may have straight line shapes extending in the first direction D 1 , but embodiments of the inventive concepts are not limited thereto. In some embodiments, the conductive line CL and the magnetic track MTR may have U-shaped line shapes. 
     The lower magnetic layer  110  may include lower magnetic domains D_L arranged in the first direction D 1 , and lower magnetic domain walls DW_L between the lower magnetic domains D_L. Each of the lower magnetic domains D_L may be a region in the lower magnetic layer  110  in which magnetic moments are aligned in a certain direction, and each of the lower magnetic domain walls DW_L may be a region in which directions of magnetic moments are changed between the lower magnetic domains D_L. The lower magnetic domains D_L and the lower magnetic domain walls DW_L may be alternately arranged in the first direction D 1 . 
     The upper magnetic layer  130  may include upper magnetic domains D_U arranged in the first direction D 1 , and upper magnetic domain walls DW_U between the upper magnetic domains D_U. Each of the upper magnetic domains D_U may be a region in the upper magnetic layer  130  in which magnetic moments are aligned in a certain direction, and each of the upper magnetic domain walls DW_U may be a region in which directions of magnetic moments are changed between the upper magnetic domains D_U. The upper magnetic domains D_U and the upper magnetic domain walls DW_U may be alternately arranged in the first direction D 1 . The upper magnetic domains D_U may vertically overlap with the lower magnetic domains D_L in the third direction D 3 , respectively. 
     The lower magnetic layer  110  and the upper magnetic layer  130  may be antiferromagnetically coupled to each other by the spacer layer  120 . Each of the lower magnetic layer  110  and the upper magnetic layer  130  may include a magnetic element and may include at least one of, for example, cobalt (Co), iron (Fe), and/or nickel (Ni). The spacer layer  120  may include a non-magnetic metal and may include, for example, ruthenium (Ru), iridium (Ir), tungsten (W), tantalum (Ta), and/or any alloy thereof. 
     In some embodiments, the lower magnetic domains D_L in the lower magnetic layer  110  and the upper magnetic domains D_U in the upper magnetic layer  130  may have perpendicular magnetic anisotropy (PMA). Each of the lower magnetic domains D_L in the lower magnetic layer  110  may have a magnetization direction  110 M substantially perpendicular to an interface between the lower magnetic layer  110  and the spacer layer  120 , and the magnetization directions  110 M of lower magnetic domains D_L adjacent directly to each other may be opposite to each other. Each of the lower magnetic domain walls DW_L may define a boundary between the adjacent lower magnetic domains D_L having the magnetization directions  110 M opposite to each other. Each of the upper magnetic domains D_U in the upper magnetic layer  130  may have a magnetization direction  130 M substantially perpendicular to an interface between the upper magnetic layer  130  and the spacer layer  120 , and the magnetization directions  130 M of upper magnetic domains D_U adjacent directly to each other may be opposite to each other. Each of the upper magnetic domain walls DW_U may define a boundary between the adjacent upper magnetic domains D_U having the magnetization directions  130 M opposite to each other. 
     The upper magnetic domains D_U may vertically overlap with the lower magnetic domains D_L in the third direction D 3 , respectively, and the upper magnetic domains D_U and the lower magnetic domains D_L may be antiferromagnetically coupled to each other by the spacer layer  120 . The magnetization direction  130 M of each of the upper magnetic domains D_U may be antiparallel to the magnetization direction  110 M of a corresponding lower magnetic domain D_L of the lower magnetic domains D_L. 
     The magnetic track MTR may further include a non-magnetic pattern  140  disposed on the spacer layer  120  and at a side of the upper magnetic layer  130 . The non-magnetic pattern  140  may vertically overlap with a portion of the lower magnetic layer  110  in the third direction D 3 . For example, the non-magnetic pattern  140  may vertically overlap with a corresponding lower magnetic domain D_L of the lower magnetic domains D_L in the lower magnetic layer  110  (e.g., in the third direction D 3 ). The corresponding lower magnetic domain D_L may have the magnetization direction  110 M substantially perpendicular to the interface between the lower magnetic layer  110  and the spacer layer  120 . 
     The spacer layer  120  may be disposed between the lower magnetic layer  110  and the upper magnetic layer  130  and may extend between the non-magnetic pattern  140  and the portion of the lower magnetic layer  110  (i.e., the portion that vertically overlaps in the third direction D 3  with the non-magnetic pattern  140 ). The non-magnetic pattern  140  may include a metal oxide. The non-magnetic pattern  140  may include a same magnetic element as a magnetic element in the upper magnetic layer  130  and may further include oxygen. 
     The non-magnetic pattern  140  may be in contact with a side surface  130 S of the upper magnetic layer  130 . The side surface  130 S of the upper magnetic layer  130  may be referred to as a junction surface  130 S between the non-magnetic pattern  140  and the upper magnetic layer  130 . The non-magnetic pattern  140  may have a first surface  140 S 1  and a second surface  140 S 2 , which are opposite to each other in the second direction D 2 . The junction surface  130 S between the non-magnetic pattern  140  and the upper magnetic layer  130  may be inclined with respect to a reference surface SS perpendicular to the first surface  140 S 1  and the second surface  140 S 2  of the non-magnetic pattern  140 . The reference surface SS may be a surface perpendicular to the first direction D 1  and parallel to a plane formed by the second direction D 2  and the third direction D 3 . An angle θj between the junction surface  130 S and the reference surface SS may be greater than 30 degrees. For example, the angle θj between the junction surface  130 S and the reference surface SS may be greater than 30 degrees and less than 90 degrees. The non-magnetic pattern  140  may have a length  140 L in the first direction D 1 . The length  140 L of the non-magnetic pattern  140  in the first direction D 1  may become progressively greater from the first surface  140 S 1  toward the second surface  140 S 2 . In other words, a length in the first direction D 1  of the second surface  140 S 2  of the non-magnetic pattern  140  may be greater than a length in the first direction D 1  of the first surface  140 S 1  of the non-magnetic pattern  140 . 
     The magnetic track MTR may include a synthetic antiferromagnetic region SAF and a ferromagnetic region FM. The synthetic antiferromagnetic region SAF may be a region in which the lower magnetic layer  110  and the upper magnetic layer  130  are antiferromagnetically coupled to each other by the spacer layer  120 . The ferromagnetic region FM may include the non-magnetic pattern  140 , and the portion (i.e., the corresponding lower magnetic domain D_L) of the lower magnetic layer  110 , which vertically overlaps with the non-magnetic pattern  140 . The magnetic track MTR may have a ferromagnet-synthetic antiferromagnet (FM-SAF) lateral junction structure in which the ferromagnetic region FM and the synthetic antiferromagnetic region SAF are joined to each other in the first direction D 1 . The junction surface  130 S between the non-magnetic pattern  140  and the upper magnetic layer  130  may also be referred to as a junction surface  130 S between the ferromagnetic region FM and the synthetic antiferromagnetic region SAF. 
     The ferromagnetic region FM of the magnetic track MTR may be a region used to inject a magnetic domain wall (e.g., the lower magnetic domain walls DW_L) into the synthetic antiferromagnetic region SAF of the magnetic track MTR for initialization of the magnetic memory device. 
     When a current flows in the first direction D 1  or the opposite direction to the first direction D 1  in the conductive line CL, the lower magnetic domain walls DW_L in the lower magnetic layer  110  may move in the first direction D 1 . The movement of the lower magnetic domain walls DW_L may be due to spin-orbit torque and Dzyaloshinskii-Moriya interaction (DMI) generated at an interface between the conductive line CL and the lower magnetic layer  110 . A movement direction of the lower magnetic domain walls DW_L may be dependent on chirality of the lower magnetic domain walls DW_L. Since the lower magnetic domain walls DW_L in the lower magnetic layer  110  move in the first direction D 1 , the upper magnetic domain walls DW_U in the upper magnetic layer  130  may also move in the first direction D 1 . The movement of the upper magnetic domain walls DW_U may be due to the antiferromagnetic coupling between the lower magnetic layer  110  and the upper magnetic layer  130 . 
     The read/write unit  150  may be disposed on the synthetic antiferromagnetic region SAF of the magnetic track MTR. The read/write unit  150  may include a GMR sensor using a giant magneto resistance effect or a TMR sensor using a tunnel magneto resistance effect. For example, the read/write unit  150  may include a magnetic pattern  154  on the upper magnetic layer  130 , a tunnel barrier pattern  152  between the upper magnetic layer  130  and the magnetic pattern  154 , and an electrode pattern  156  on the magnetic pattern  154 . The magnetic pattern  154  may be disposed between the tunnel barrier pattern  152  and the electrode pattern  156 . The magnetic pattern  154  may include at least one of cobalt (Co), iron (Fe), and/or nickel (Ni). The tunnel barrier pattern  152  may include at least one of magnesium (Mg) oxide, titanium (Ti) oxide, aluminum (Al) oxide, magnesium-zinc (Mg-Zn) oxide, and/or magnesium-boron (Mg-B) oxide. The electrode pattern  156  may include a conductive material and may include, for example, a metal (e.g., copper, tungsten, or aluminum) and/or a metal nitride (e.g., tantalum nitride, titanium nitride, and/or tungsten nitride). 
     The read/write unit  150  may vertically overlap with a corresponding upper magnetic domain D_U of the upper magnetic domains D_U in the upper magnetic layer  130  and a corresponding lower magnetic domain D_L of the lower magnetic domains D_L in the lower magnetic layer  110  (e.g., in the third direction D 3 ). 
     In some embodiments, the magnetic pattern  154  of the read/write unit  150  may have perpendicular magnetic anisotropy (PMA). The magnetic pattern  154  may have a magnetization direction  154 M substantially perpendicular to an interface between the magnetic pattern  154  and the tunnel barrier pattern  152 , and the magnetization direction  154 M of the magnetic pattern  154  may be fixed in one direction. The magnetization directions  130 M of the upper magnetic domains D_U in the upper magnetic layer  130  and the magnetization directions  110 M of the lower magnetic domains D_L in the lower magnetic layer  110  may be changeable to be parallel or antiparallel to the magnetization direction  154 M of the magnetic pattern  154 . 
     The magnetic pattern  154  may vertically overlap with a corresponding upper magnetic domain D_U of the upper magnetic domains D_U and a corresponding lower magnetic domain D_L of the lower magnetic domains D_L (e.g., in the third direction D 3 ). The magnetic pattern  154 , the corresponding upper magnetic domain D_U and the corresponding lower magnetic domain D_L, which vertically overlap with each other, may constitute a magnetic tunnel junction MTJ. The magnetic pattern  154  may be a pinned layer having the magnetization direction  154 M fixed in one direction, and the corresponding upper magnetic domain D_U and the corresponding lower magnetic domain D_L may be antiferromagnetically coupled to each other to constitute a free layer having a synthetic antiferromagnetic structure. 
     In a read operation, a read current Tread may flow through the magnetic tunnel junction MTJ. A resistance state of the magnetic tunnel junction MTJ may be detected by the read current Tread. Whether the magnetic tunnel junction MTJ is in a high-resistance state or a low-resistance state may be detected by the read current Tread. Data (0 or 1) stored in the free layer may be detected from the resistance state of the magnetic tunnel junction MTJ. In a write operation, a write current Isw may flow through the magnetic tunnel junction MTJ. A magnitude of the write current Isw may be greater than a magnitude of the read current Tread. The magnetization direction  130 M of the corresponding upper magnetic domain D_U may be switched by spin transfer torque generated by the write current Isw. The magnetization direction  130 M of the corresponding upper magnetic domain D_U may be switched to be parallel or antiparallel to the magnetization direction  154 M of the magnetic pattern  154 , by the spin transfer torque generated by the write current Isw. The magnetization direction  110 M of the corresponding lower magnetic domain D_L may be switched to be antiparallel to the magnetization direction  130 M of the corresponding upper magnetic domain D_U, by the antiferromagnetic coupling between the corresponding upper magnetic domain D_U and the corresponding lower magnetic domain D_L. 
     In some embodiments, each of the lower magnetic layer  110 , the upper magnetic layer  130 , and the magnetic pattern  154  may include at least one of cobalt (Co), iron (Fe), and/or nickel (Ni) and may further include one or more 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/or nitrogen (N). For example, each of the lower magnetic layer  110 , the upper magnetic layer  130  and the magnetic pattern  154  may include at least one of a perpendicular magnetic material (e.g., CoFeTb, CoFeGd, and/or CoFeDy), a perpendicular magnetic material having a L 1   0  structure, a CoPt alloy having a hexagonal close packed (HCP) lattice structure, and/or a perpendicular magnetic structure. The perpendicular magnetic material having the L 1   0  structure may include at least one of FePt having the L 1   0  structure, FePd having the L 1   0  structure, CoPd having the L 1   0  structure, or CoPt having the L 1   0  structure. The perpendicular magnetic structure may include magnetic layers and non-magnetic layers, which are alternately and repeatedly stacked. For example, the perpendicular 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, and/or (CoCr/Pd)n, where ‘n’ denotes the number of bilayers. In certain embodiments, each of the lower magnetic layer  110 , the upper magnetic layer  130  and the magnetic pattern  154  may include CoFeB and/or a Co-based Heusler alloy. 
       FIGS.  3 A to  6 A  are plan views corresponding to a portion ‘A’ of  FIG.  1    to illustrate a method of manufacturing a magnetic memory device according to some embodiments of the inventive concepts.  FIGS.  3 B to  6 B  are cross-sectional views corresponding to a portion ‘B’ of  FIG.  2    to illustrate a method of manufacturing a magnetic memory device according to some embodiments of the inventive concepts. Hereinafter, the descriptions of the same features as mentioned with reference to  FIGS.  1  and  2    will be omitted for the purpose of ease and convenience in explanation. 
     Referring to  FIGS.  3 A and  3 B , a first magnetic layer  110   a , a non-magnetic layer  120   a , and a second magnetic layer  130   a  may be sequentially stacked on a conductive layer CLa. The conductive layer CLa, the first magnetic layer  110   a , the non-magnetic layer  120   a , and the second magnetic layer  130   a  may be formed using a chemical vapor deposition (CVD) method and/or a physical vapor deposition (PVD) method and may be formed using, for example, a sputtering deposition method. A first mask pattern M 1  may be formed on the second magnetic layer  130   a . The first mask pattern M 1  may have a line shape extending in the first direction D 1  and may be a photoresist pattern or a hard mask pattern. 
     Referring to  FIGS.  4 A and  4 B , the second magnetic layer  130   a , the non-magnetic layer  120   a , the first magnetic layer  110   a , and the conductive layer CLa may be sequentially etched using the first mask pattern M 1  as an etch mask. The second magnetic layer  130   a , the non-magnetic layer  120   a , the first magnetic layer  110   a  and the conductive layer CLa may be sequentially etched by, for example, an ion beam etching process. An upper magnetic layer  130 , a spacer layer  120 , a lower magnetic layer  110  and a conductive line CL may be formed by etching the second magnetic layer  130   a , the non-magnetic layer  120   a , the first magnetic layer  110   a  and the conductive layer CLa, respectively. The lower magnetic layer  110  and the upper magnetic layer  130  may be antiferromagnetically coupled to each other by the spacer layer  120 . 
     After the formation of the conductive line CL, the lower magnetic layer  110 , the spacer layer  120 , and the upper magnetic layer  130 , the first mask pattern M 1  may be removed. The first mask pattern M 1  may be removed by, for example, an ashing process and/or a strip process. 
     Referring to  FIGS.  5 A and  5 B , a second mask pattern M 2  may be formed on the upper magnetic layer  130 . The second mask pattern M 2  may expose a portion of the upper magnetic layer  130  and may at least partially cover a remaining portion of the upper magnetic layer  130 . The second mask pattern M 2  may be formed to have a line shape extending in the first direction D 1 , but embodiments of the inventive concepts are not limited thereto. The second mask pattern M 2  may be a photoresist pattern or a hard mask pattern. The second mask pattern M 2  may include a metal nitride and may include, for example, TaN. 
     A side surface M 2 _S of the second mask pattern M 2  may be adjacent to the exposed portion of the upper magnetic layer  130 . The upper magnetic layer  130  may have a first surface  130 S 1  and a second surface  130 S 2 , which are opposite to each other in the second direction D 2 . The side surface M 2 _S of the second mask pattern M 2  may be inclined with respect to a reference surface SS perpendicular to the first surface  130 S 1  and the second surface  130 S 2  of the upper magnetic layer  130  and parallel to a plane formed by the second direction D 2  and the third direction D 3 . An angle θj between the side surface M 2 _S of the second mask pattern M 2  and the reference surface SS may be greater than 30 degrees. For example, the angle θj between the side surface M 2 _S of the second mask pattern M 2  and the reference surface SS may be greater than 30 degrees and less than 90 degrees. 
     An oxidation process may be performed on the upper magnetic layer  130 . The second mask pattern M 2  may be used as a mask of the oxidation process. The oxidation process may include, for example, an oxygen plasma treatment. 
     Referring to  FIGS.  6 A and  6 B , the exposed portion of the upper magnetic layer  130  may be oxidized by the oxidation process, and thus a non-magnetic pattern  140  may be formed at a side of the upper magnetic layer  130 . The non-magnetic pattern  140  may include a metal oxide. The non-magnetic pattern  140  may include the same magnetic element as the upper magnetic layer  130  and may further include oxygen. 
     The non-magnetic pattern  140  may be in contact with a side surface  130 S of the upper magnetic layer  130 . The side surface  130 S of the upper magnetic layer  130  may be referred to as a junction surface  130 S between the non-magnetic pattern  140  and the upper magnetic layer  130 . The non-magnetic pattern  140  may have a first surface  140 S 1  and a second surface  140 S 2 , which are opposite to each other in the second direction D 2 . The junction surface  130 S between the non-magnetic pattern  140  and the upper magnetic layer  130  may be inclined with respect to the reference surface SS perpendicular to the first surface  140 S 1  and the second surface  140 S 2  of the non-magnetic pattern  140  and parallel to a plane formed by the second direction D 2  and the third direction D 3 . An angle θj between the junction surface  130 S and the reference surface SS may be greater than 30 degrees. For example, the angle θj between the junction surface  130 S and the reference surface SS may be greater than 30 degrees and less than 90 degrees. The non-magnetic pattern  140  may have a length  140 L in the first direction D 1 . The length  140 L of the non-magnetic pattern  140  in the first direction D 1  may become progressively greater from the first surface  140 S 1  toward the second surface  140 S 2 . In other words, a length in the first direction D 1  of the second surface  140 S 2  of the non-magnetic pattern  140  may be greater than a length in the first direction D 1  of the first surface  140 S 1  of the non-magnetic pattern  140 . 
     The spacer layer  120  may be used as an oxidation stop layer of the oxidation process. Thus, a portion  110 P of the lower magnetic layer  110 , which vertically overlaps with the non-magnetic pattern  140  (e.g., in the third direction D 3 ), may not be oxidized by the oxidation process, but may maintain a ferromagnetic property. 
     After the formation of the non-magnetic pattern  140  by the oxidation process, the second mask pattern M 2  may be removed. The second mask pattern M 2  may be removed by, for example, an ashing process and/or a strip process. 
     The lower magnetic layer  110 , the spacer layer  120 , the upper magnetic layer  130 , and the non-magnetic pattern  140  may constitute a magnetic track MTR. The conductive line CL and the magnetic track MTR may have line shapes extending in the first direction D 1 . 
     The magnetic track MTR may include a synthetic antiferromagnetic region SAF and a ferromagnetic region FM. The synthetic antiferromagnetic region SAF may be a region in which the lower magnetic layer  110  and the upper magnetic layer  130  are antiferromagnetically coupled to each other by the spacer layer  120 . The ferromagnetic region FM may include the non-magnetic pattern  140 , and the portion  110 P of the lower magnetic layer  110  which vertically (i.e., D 3  direction) overlaps with the non-magnetic pattern  140 . The magnetic track MTR may have a ferromagnet-synthetic antiferromagnet (FM-SAF) lateral junction structure in which the ferromagnetic region FM and the synthetic antiferromagnetic region SAF are joined to each other in the first direction D 1 . The junction surface  130 S between the non-magnetic pattern  140  and the upper magnetic layer  130  may also be referred to as a junction surface  130 S between the ferromagnetic region FM and the synthetic antiferromagnetic region SAF. 
     Referring again to  FIGS.  1  and  2   , a read/write unit  150  may be formed on the synthetic antiferromagnetic region SAF of the magnetic track MTR. For example, the formation of the read/write unit  150  may include sequentially forming a tunnel insulating layer, a magnetic layer, and an electrode layer on the magnetic track MTR, and etching the tunnel insulating layer, the magnetic layer and the electrode layer. A tunnel barrier pattern  152 , a magnetic pattern  154  and an electrode pattern  156  may be formed by etching the tunnel insulating layer, the magnetic layer, and the electrode layer, respectively. 
       FIGS.  7 A to  7 D  are cross-sectional views corresponding to the portion ‘B’ of  FIG.  2    to illustrate a method for initializing a magnetic memory device according to some embodiments of the inventive concepts. Hereinafter, the descriptions of the same features as mentioned with reference to  FIGS.  1  and  2    will be omitted for the purpose of ease and convenience in explanation. 
     Referring to  FIG.  7 A , a magnetic memory device may include a conductive line CL and a magnetic track MTR on the conductive line CL. The magnetic track MTR may include a lower magnetic layer  110 , a spacer layer  120  and an upper magnetic layer  130  which are sequentially stacked on the conductive line CL and may further include a non-magnetic pattern  140  disposed on the spacer layer  120  and at a side of the upper magnetic layer  130 . The non-magnetic pattern  140  may vertically overlap with a portion  110 P of the lower magnetic layer  110  in the third direction D 3 . The magnetic track MTR may include a synthetic antiferromagnetic region SAF in which the lower magnetic layer  110  and the upper magnetic layer  130  are antiferromagnetically coupled to each other by the spacer layer  120 , and a ferromagnetic region FM including the non-magnetic pattern  140  and the portion  110 P of the lower magnetic layer  110 , which vertically overlap with each other (e.g., in the third direction D 3 ). A junction surface  130 S between the ferromagnetic region FM and the synthetic antiferromagnetic region SAF (i.e., a junction surface between the non-magnetic pattern  140  and the upper magnetic layer  130 ) may be inclined with respect to the reference surface SS perpendicular to the first surface  140 S 1  and the second surface  140 S 2  of the non-magnetic pattern  140 , as described with reference to  FIGS.  1  and  2   . 
     In some embodiments, the lower magnetic layer  110  may have a magnetization direction  110 M substantially perpendicular to an interface between the lower magnetic layer  110  and the spacer layer  120 , and the upper magnetic layer  130  may have a magnetization direction  130 M substantially perpendicular to an interface between the upper magnetic layer  130  and the spacer layer  120 . The lower magnetic layer  110  and the upper magnetic layer  130  may be antiferromagnetically coupled to each other by the spacer layer  120 , and thus the magnetization direction  130 M of the upper magnetic layer  130  may be antiparallel to the magnetization direction  110 M of the lower magnetic layer  110 . For example, the magnetization direction  110 M of the lower magnetic layer  110  may be aligned in an up-direction, and the magnetization direction  130 M of the upper magnetic layer  130  may be aligned in a down-direction. 
     An initial magnetization direction  110 Mi of the portion  110 P of the lower magnetic layer  110 , which vertically overlaps with the non-magnetic pattern  140  may be the same as the magnetization direction  110 M of the lower magnetic layer  110 . For example, the initial magnetization direction  110 Mi of the portion  110 P of the lower magnetic layer  110  may be aligned in the up-direction. 
     Referring to  FIG.  7 B , an external magnetic field H 1  may be applied to the magnetic track MTR. A direction of the external magnetic field H 1  may be an opposite direction to the initial magnetization direction  110 Mi of the portion  110 P of the lower magnetic layer  110 . For example, the direction of the external magnetic field H 1  may be the down-direction. 
     A coercivity (Hc) of the synthetic antiferromagnetic region SAF of the magnetic track MTR may be greater than a coercivity (Hc) of the ferromagnetic region FM of the magnetic track MTR. Since the synthetic antiferromagnetic region SAF of the magnetic track MTR has a relatively greater coercivity (Hc), the magnetization directions  110 M and  130 M of the lower magnetic layer  110  and the upper magnetic layer  130  in the synthetic antiferromagnetic region SAF of the magnetic track MTR may not be reversed by the external magnetic field H 1 . Since the ferromagnetic region FM of the magnetic track MTR has a relatively lower coercivity (Hc), the initial magnetization direction  110 Mi of the portion  110 P of the lower magnetic layer  110  in the ferromagnetic region FM of the magnetic track MTR may be reversed by the external magnetic field H 1 . Thus, the portion  110 P of the lower magnetic layer  110  may have a first magnetization direction  110 M 1  aligned in the down-direction. 
     Since the initial magnetization direction  110 Mi of the portion  110 P of the lower magnetic layer  110  is reversed to the first magnetization direction  110 M 1  by the external magnetic field H 1 , a lower magnetic domain wall DW_L may be formed in the portion  110 P of the lower magnetic layer  110 , which is adjacent to the junction between the ferromagnetic region FM and the synthetic antiferromagnetic region SAF. 
     Referring to  FIG.  7 C , a current I may be applied to flow in the conductive line CL in the first direction D 1  (or the opposite direction to the first direction D 1 ). Thus, the lower magnetic domain wall DW_L formed in the portion  110 P of the lower magnetic layer  110  in the ferromagnetic region FM may be injected into the lower magnetic layer  110  in the synthetic antiferromagnetic region SAF. For example, the lower magnetic domain wall DW_L may move in the first direction D 1 . 
     To inject the lower magnetic domain wall DW_L from the ferromagnetic region FM into the synthetic antiferromagnetic region SAF, a relatively greater current density may be required in the conductive line CL. 
     According to the inventive concepts, as described with reference to  FIGS.  1  and  2   , the junction surface  1305  between the ferromagnetic region FM and the synthetic antiferromagnetic region SAF (i.e., the junction surface between the non-magnetic pattern  140  and the upper magnetic layer  130 ) may be inclined with respect to the reference surface SS perpendicular to the first surface  140 S 1  and the second surface  140 S 2  of the non-magnetic pattern  140 , and the angle θj between the junction surface  130 S and the reference surface SS may be greater than 30 degrees. Thus, it may be possible to reduce the current density applied to the conductive line CL to inject the lower magnetic domain wall DW_L from the ferromagnetic region FM into the synthetic antiferromagnetic region SAF. In other words, it may be possible to reduce the current density for injecting a magnetic domain wall (e.g., the lower magnetic domain wall DW_L) into the magnetic track MTR including the synthetic antiferromagnetic region SAF. As a result, it may be possible to provide the magnetic memory device configured to inject the magnetic domain wall (e.g., the lower magnetic domain wall DW_L) into the magnetic track MTR including the synthetic antiferromagnetic region SAF. 
     Referring to  FIG.  7 D , by or in response to the current I applied to the conductive line CL, the lower magnetic domain wall DW_L may be injected into the lower magnetic layer  110  in the synthetic antiferromagnetic region SAF and may move in the lower magnetic layer  110  in the synthetic antiferromagnetic region SAF in the first direction D 1 . With the movement of the lower magnetic domain wall DW_L, the magnetization direction  110 M of the lower magnetic layer  110  may be reversed to the first magnetization direction  110 M 1  aligned in the down-direction. 
     By the antiferromagnetic coupling between the upper magnetic layer  130  and the lower magnetic layer  110 , the magnetization direction  130 M of the upper magnetic layer  130  may be reversed to be antiferromagnetically coupled to the first magnetization direction  110 M 1  of the lower magnetic layer  110 . A reversed magnetization direction  130 M 1  of the upper magnetic layer  130  may be antiferromagnetically coupled to the first magnetization direction  110 M 1  of the lower magnetic layer  110  and may be aligned in, for example, the up-direction. Since the upper magnetic layer  130  has the reversed magnetization direction  130 M 1 , an upper magnetic domain wall DW_U may be formed in the upper magnetic layer  130 . The upper magnetic domain wall DW_U may vertically overlap with the lower magnetic domain wall DW_L (e.g., in the third direction D 3 ). 
       FIGS.  8  and  9    are graphs showing a current density for injecting a magnetic domain wall into a magnetic track of a magnetic memory device according to some embodiments of the inventive concepts. 
       FIG.  8    shows a current density J according to a pulse width τ p  of the current I applied to the conductive line CL to inject the lower magnetic domain wall DW_L from the ferromagnetic region FM of the magnetic track MTR into the synthetic antiferromagnetic region SAF of the magnetic track MTR. It may be recognized that the current density J is reduced under a condition of the same pulse width τ p  of the current I when the angle θj between the reference surface SS and the junction surface  130 S between the ferromagnetic region FM and the synthetic antiferromagnetic region SAF is greater than 30 degrees (e.g., θj=45° or θj=60°. 
       FIG.  9    shows a current density J applied to the conductive line CL to inject the lower magnetic domain wall DW_L from the ferromagnetic region FM into the synthetic antiferromagnetic region SAF, according to the angle θj between the reference surface SS and the junction surface  130 S between the ferromagnetic region FM and the synthetic antiferromagnetic region SAF. It may be recognized that the current density J applied to the conductive line CL is reduced when the angle θj between the reference surface SS and the junction surface  130 S between the ferromagnetic region FM and the synthetic antiferromagnetic region SAF is greater than  30  degrees (e.g., θj=45° or θj=60°. 
       FIG.  10    is a cross-sectional view illustrating a magnetic memory device according to some embodiments of the inventive concepts. Hereinafter, differences between the present embodiments and the above embodiments of  FIGS.  1  and  2    will be mainly described for the purpose of ease and convenience in explanation. 
     Referring to  FIGS.  1  and  10   , the lower magnetic domains D_L in the lower magnetic layer  110  and the upper magnetic domains D_U in the upper magnetic layer  130  may have in-plane magnetic anisotropy (IMA). Each of the lower magnetic domains D_L in the lower magnetic layer  110  may have a magnetization direction  110 M parallel to an interface between the lower magnetic layer  110  and the spacer layer  120 , and magnetization directions  110 M of lower magnetic domains D_L adjacent directly to each other may be opposite to each other. Each of the lower magnetic domain walls DW_L may define a boundary between the adjacent lower magnetic domains D_L having the magnetization directions  110 M opposite to each other. Each of the upper magnetic domains D_U in the upper magnetic layer  130  may have a magnetization direction  130 M parallel to an interface between the upper magnetic layer  130  and the spacer layer  120 , and magnetization directions  130 M of upper magnetic domains D_U adjacent directly to each other may be opposite to each other. Each of the upper magnetic domain walls DW_U may define a boundary between the adjacent upper magnetic domains D_U having the magnetization directions  130 M opposite to each other. 
     The magnetic pattern  154  of the read/write unit  150  may have in-plane magnetic anisotropy (IMA). The magnetic pattern  154  may have a magnetization direction  154 M parallel to an interface between the magnetic pattern  154  and the tunnel barrier pattern  152 , and the magnetization direction  154 M of the magnetic pattern  154  may be fixed in one direction. The magnetization directions  130 M of the upper magnetic domains D_U in the upper magnetic layer  130  and the magnetization directions  110 M of the lower magnetic domains D_L in the lower magnetic layer  110  may be changeable to be parallel or antiparallel to the magnetization direction  154 M of the magnetic pattern  154 . 
     In some embodiments, each of the lower magnetic layer  110 , the upper magnetic layer  130  and the magnetic pattern  154  may include a ferromagnetic material, and the magnetic pattern  154  may further include an antiferromagnetic material for pinning or fixing a magnetization direction of the ferromagnetic material. 
     Except for the aforementioned differences, other features and components of the magnetic memory device according to the present embodiments may be substantially the same as corresponding features and components of the magnetic memory device described with reference to  FIGS.  1  and  2   . In addition, the magnetic memory device according to the present embodiments may be formed by substantially the same method as described with reference to  FIGS.  3 A to  6 A and  3 B to  6 B  and may be initialized by substantially the same method as described with reference to  FIGS.  7 A to  7 D . 
     According to the inventive concepts, the magnetic memory device may include the conductive line and the magnetic track on the conductive line, and the conductive line and the magnetic track may extend in the first direction. The magnetic track may have the ferromagnet-synthetic antiferromagnet (FM-SAF) lateral junction structure in which the ferromagnetic region and the synthetic antiferromagnetic region are joined to each other in the first direction. The junction surface between the ferromagnetic region and the synthetic antiferromagnetic region may be inclined with respect to the reference surface perpendicular to the first direction, and the angle between the junction surface and the reference surface may be greater than 30 degrees. Thus, it may be possible to reduce a current density applied to the conductive line to inject a magnetic domain wall from the ferromagnetic region into the synthetic antiferromagnetic region. In other words, it may be possible to reduce the current density for injecting the magnetic domain wall into the magnetic track including the synthetic antiferromagnetic region. As a result, it may be possible to provide a magnetic memory device configured to inject a magnetic domain wall into the magnetic track including the synthetic antiferromagnetic region. 
     While example embodiments of the inventive concepts have been particularly shown and described, it will be understood by one of ordinary skill in the art that variations in form and detail may be made therein without departing from the spirit and scope of the attached claims.