Patent Publication Number: US-11024726-B2

Title: Skyrmion diode and method of manufacturing the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional application of U.S. application Ser. No. 15/431,488 filed on Feb. 13, 2017, which claims the benefit of Korean Patent Application No. 10-2016-0026930, filed on Mar. 7, 2016, which are incorporated herein by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a skyrmion diode, more particularly, to a skyrmion diode using skyrmions as information carriers and a method of manufacturing the skyrmion diode. 
     BACKGROUND 
     As well known in the art, semiconductor technology so far has been developed according to Moore&#39;s law. However, quantum phenomena occur as feature sizes of semiconductor devices are continuously scaled down, and therefore, a design rule that has been previously employed has to be changed. 
     New challenges and approaches have been attempted to break away from silicon-based device concepts in consideration of, e.g., heat problems due to drastic increases in power consumption, slowing of information processing speed, and rapid increase in manufacturing equipment and process costs. In this connection, various studies and researches have been devoted to overcome the current technical limitations. 
     For example, conventionally, there is disclosed ‘a method of generating and erasing skyrmion and magnetic element’ in Japanese Patent Application Publication No. 2014-175417 (published on Sep. 22, 2014). 
     In this conventional case, corners are provided in a magnetic body having a skyrmion phase, and skyrmion is generated by applying current across the corners in a state where a magnetic field is applied in a predetermined intensity range. 
     However, since the magnetic body has to be formed in a shape having the corners, a limited manufacturing process such as a slurry molding can only be used. Further, electrical characteristics vary depending on the shape, size or position of the corner, but it is difficult to perform a fine adjustment for the electrical characteristics, which is problematic. 
     SUMMARY 
     In view of the above, the present disclosure provides a skyrmion diode using skyrmions as information carriers without providing corners in a magnetic body having the skyrmions and a method of manufacturing the skyrmion diode. 
     In accordance with an aspect of the present disclosure, there is provided a skyrmion diode including a magnetic body and a conductive body. The magnetic body may have a skyrmion which is used as an information carrier. The conductive body may be disposed on or under the magnetic body. The conductive body may include a Dzyaloshinskii-Moriya interaction (DMI) region and a defect region. The DMI region is provided to induce DMI in a region of the magnetic body corresponding to the DMI region by spin-orbit coupling of the conductive body and magnetic moments of the magnetic body. The defect region is provided to prevent the DMI from being induced in a region of the magnetic body corresponding to the defect region. 
     Further, spin-polarized current may be supplied to at least one of the magnetic body and the conductive body. The defect region may be formed by forming a notch portion at a side portion of the conductive body. The notch portion may have a semicircular shape, a triangular shape or a rectangular shape. 
     In accordance with another aspect of the present disclosure, there is provided a method of manufacturing a skyrmion diode, the method including: forming a magnetic body including a skyrmion, which is used as an information carrier; forming a conductive body having spin-orbit coupling on or under the magnetic body; and forming a defect region in a part of the conductive body, which prevents Dzyaloshinskii-Moriya interaction (DMI) induced by the spin-orbit coupling and magnetic moments of the magnetic body from being induced in a region of the magnetic body corresponding to the defect region. 
     Herein, the defect region may be formed by forming a notch portion at a side portion of the conductive body. The notch portion may have a semicircular shape, a triangular shape or a rectangular shape. 
     The skyrmion diode according to the aspects of the present disclosure employs a conductive body including the DMI region for inducing the DMI in the magnetic body and the defect region for preventing the DMI from being induced in the magnetic body. Therefore, the skyrmion is used as an information carrier without providing corners in the magnetic body. 
     With such configuration, various manufacturing processes can be introduced since the conductive body can be easily manufactured in various shapes as compared with the magnetic body. Further, there can be easily performed a fine adjustment of the defect region in which the electrical characteristics are varied depending on its shape, size or position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view of an exemplary skyrmion diode according to one embodiment. 
         FIG. 2  is a perspective view of an exemplary conductive body according to one embodiment. 
         FIG. 3  is a perspective view of an exemplary conductive body according to another embodiment. 
         FIG. 4  is a flow chart illustrating an exemplary method of manufacturing the skyrmion diode according to one embodiment. 
         FIG. 5  is a graph showing the diode characteristics. 
     
    
    
     DETAILED DESCRIPTION 
     The advantages and features of the present disclosure and the method for accomplishing them will be clearly understood from the following detailed description of the embodiments taken in conjunction with the accompanying drawings. However, the present disclosure is not limited to those embodiments disclosed herein below, but may be implemented in various forms. It should be noted that the embodiments are provided to make a full disclosure of the present disclosure and also to allow those skilled in the art to know the full scope of the present disclosure. Therefore, the present disclosure will be defined only by the scope of the appended claims. 
     In the following description, well-known functions and/or constitutions will not be described in detail if they would unnecessarily obscure the features of the present disclosure in unnecessary detail. Further, the terms to be described below are defined in consideration of their functions in the embodiments of the present disclosure and may vary depending on user&#39;s or operator&#39;s intention or practice. Accordingly, the definition may be made on the basis of the content throughout the specification. 
     Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. 
       FIG. 1  is an exploded perspective view of an exemplary skyrmion diode according to one embodiment.  FIG. 2  is a perspective view of an exemplary conductive body according to one embodiment.  FIG. 3  is a perspective view of an exemplary conductive body according to another embodiment. As shown in  FIGS. 1 to 3 , a skyrmion diode  100  includes a magnetic body  110  and a conductive body  120 . 
     The magnetic body  110  is disposed on or under the conductive body  120  and has a skyrmion serving as an information carrier. 
     When spin-polarized current is supplied to at least one of the magnetic body  110  and the conductive body  120 , spin-transfer torque is generated to move the skyrmion. In addition, since the conductive body  120  has strong spin-orbit coupling, spin-orbit torque can be generated by a spin Hall effect or a rashba effect to thereby move the skyrmion. 
     The conductive body  120  includes a Dzyaloshinskii-Moriya interaction (DMI) region  121  for inducing DMI in a region of the magnetic body  110  corresponding to the DMI region  121  by magnetic moments of the magnetic body  110  and a spin-orbit coupling of the conductive body  120 . Further, the conductive body  120  includes a defect region  122  to prevent the DMI from being induced in a region of the magnetic body  110  corresponding to the defect region  122  (that is, a region of the magnetic body  110  other than the region corresponding to the DMI region) in spite of the magnetic moments of the magnetic body  110  and the spin-orbit coupling of the conductive body  120 . 
     The defect region  122  may be formed by forming a notch portion at a side portion of the conductive body  120 . For example, the notch portion is formed by cutting away a part of a longitudinal side portion of the conductive body  120  having a rectangular shape and is positioned on a left longitudinal side portion or a right longitudinal side portion of  FIG. 1  depending on the diode characteristic of e.g., a forward direction or a reverse direction. Further, the notch portion may be formed in a semicircular shape as shown in  FIG. 1  or a triangular shape as shown in  FIG. 2 . Alternatively, the notch portion may be formed in a rectangular shape as shown in  FIG. 3 . 
       FIG. 4  is a flow chart illustrating an exemplary method of manufacturing the skyrmion diode according to one embodiment, wherein the magnetic body  110  is formed first. 
     In the method, a step S 210  of forming the magnetic body  110  is carried out first. For example, the magnetic body  110  can be formed by using a process such as a slurry molding. An alloy-based magnetic material such as a cobalt-iron (CoFe) alloy, a cobalt-iron-boron (CoFeB) alloy or the like, or a Heusler alloy-based magnetic material such as a cobalt-ferrosilicon (Co 2 FeSi) alloy, a cobalt-manganese-silicon (Co 2 MnSi) alloy or the like can be used to form the magnetic body  110 . 
     Then, a step S 220  of forming the conductive body  120  on or above the magnetic body  110  is carried out. For example, the conductive body  120  can be formed by using a process such as a sputtering, a molecular beam epitaxy (MBE), an atomic layer deposition (ALD), a pulse laser deposition (PLD), or an E-beam evaporator. A heavy metal such as platinum (Pt), tantalum (Ta), iridium (Ir) or the like may used to form the conductive body  120 . 
     Next, a step S 230  of forming the defect region  122  in the conductive body  120  is carried out to prevent the DMI from being induced in the region of the magnetic body  110  corresponding to the defect region  122  in spite of the magnetic moments of the magnetic body  110  and the spin-orbit coupling of the conductive body  120 . For example, the defect region  122  may be formed by forming a notch portion at a side portion of the conductive body  120  through a photo etching process. The notch portion may be formed in, e.g., a semicircular shape, a triangular shape, or a rectangular shape. The electrical performance of the skyrmion diode  100  may be controlled by adjusting at least one of the shape, size and position of the notch portion. 
     The skyrmion diode  100  according to one embodiment includes the magnetic body  110  disposed on or under the conductive body  120 , and a skyrmion in the magnetic body  110  can be moved by spin polarized current. Further, since the skyrmion moves only through the region where the DMI is induced, the region of the magnetic body  110  corresponding to the DMI region  121  serves as a waveguide. When the skyrmion moving through the waveguide reach the region of the magnetic body  110  where no DMI is induced due to the defect region  122 , there occurs an interaction which causes the skyrmion to selectively turn around the defect region  122  in a specific direction, e.g., in a clockwise or counterclockwise direction based a spin orientation. Based on this interaction, the diode characteristics can be realized by allowing current-induced skyrmion to flow and move in one direction. 
       FIG. 5  is a graph showing the diode characteristics. A horizontal axis (X-axis) indicates conduction electron velocity Vs (m/s) and a vertical axis (Y-axis) indicates skyrmion velocity Vd (m/s). If the intensity of the current corresponding to the conduction electron velocity is larger than that of a critical current, the skyrmion becomes an ON state where it can pass by the defect region. If the intensity of the current corresponding to the conduction electron velocity is smaller than that of the critical current, the skyrmion becomes an OFF state where it cannot pass by the defect region. Further, as shown in  FIG. 5 , it can be seen that the intensity of the critical current in the forward direction is different from the intensity of the critical current in the reverse direction. 
     The explanation as set forth above merely provides a technical idea of the present disclosure, and it will be understood by those skilled in the art to which the present disclosure belongs that various changes and modifications may be made without departing from the scope of the characteristics of the present disclosure. Therefore, the embodiments disclosed in the present disclosure are not used to limit the technical idea of the present disclosure, but to explain the present disclosure, and the scope of the technical idea of the present disclosure is not limited to these embodiments. 
     The scope of protection of the present disclosure should be construed as defined in the following claims, and all technical ideas that fall within the equivalent technical idea of the present disclosure are intended to be embraced by the scope of protection of the present disclosure.