Abstract
Stacking a magnetic memory junction in spintronic devices necessarily involves making contacts with a transitional-metal capping electrode. Herein, by means of first-principles calculations, we reveal the importance of heavy transition-metal capping on magnetic-phase transition from antiferromagnetic (AFM) to ferromagnetic (FM) order and the large perpendicular magnetic anisotropy (PMA) found in Ta-capped FeRh films on MgO substrate. While magnetization of FeRh films reorients from in-plane to PMA when in contact with MgO, the presence of Ta capping further enhances the magnitude of the PMA energy by at least five times. This large PMA is associated with the AFM-FM transition at the interface, which in turn modifies the out-of-plane Fe 3d orbital states through the hybridization with the strong spin-orbit coupled Ta 5d orbitals. Furthermore, the magnetic-phase transition at the interface is the result of the mutual mechanisms of the capping-induced volume/tetragonal expansion in the interfacial FeRh layers and the competition between the direct and indirect exchange interactions. These findings suggest that Ta/FeRh/MgO multilayers may represent highly favourable memory materials with net interfacial ferromagnetism and large PMA in antiferromagnet spintronics.
Highlights
Capped ferromagnets (FM) on insulating MgO (HTM/FM/MgO) have been very successful for their applications in spin-transfer torque (STT) memory, owing to their large magnetoresistance (MR) and perpendicular magnetic anisotropy (PMA)[1]
57Fe conversion electron Mossbauer spectroscopy experiments[8] and first-principles calculations[15] reveal the strain and electric-field reversal induced spin reorientation of the easy magnetization axis at the magnetic-phase transition of FeRh films on MgO and BaTiO3 substrate. These results suggest that FeRh thin films have potential for STT technologies and for utilization in novel emerging memory applications such as heat-assisted magnetic recording (HAMR)[16] and magnetoelectric random access memory (MeRAM)[9,10]
In accordance with a realistic situation, we explore supercells composed of 2–7 unit cell FeRh layers (n), which are approximately 0.6–3 nm thick, on five atomic layers (ALs) of the MgO substrate capped by three ALs of Ta atoms
Summary
Capped ferromagnets (FM) on insulating MgO (HTM/FM/MgO) have been very successful for their applications in spin-transfer torque (STT) memory, owing to their large magnetoresistance (MR) and perpendicular magnetic anisotropy (PMA)[1]. These results suggest that FeRh thin films have potential for STT technologies and for utilization in novel emerging memory applications such as heat-assisted magnetic recording (HAMR)[16] and magnetoelectric random access memory (MeRAM)[9,10]
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