Correlation of interfacial perpendicular magnetic anisotropy and interlayer exchange coupling in CoFe/W/CoFe structures

Abstract

Spin transfer torque magnetic random-access memory is widely considered as a promising candidate for a next generation cache, with a core device of magnetic tunnel junction. The MgO/CoFeB/W/CoFeB/MgO structure as recording layer for magnetic tunnel junctions is of great interest due to features such as strong perpendicular magnetic anisotropy (PMA) and thermal stability. However, the origin of correlation between PMA and interlayer exchange coupling (IEC) in this structure remains unclear. In this paper, we investigate the PMA and IEC in the MgO/CoFe/W/CoFe/MgO structure with first-principles calculation. IEC with long and short period oscillations is observed, which results in much different magnetic anisotropy energies at CoFe/W interface in MgO/CoFe/W/CoFe/MgO structure compared to MgO/CoFe/W structure. Furthermore, we find an oscillation of magnetic anisotropy energies in ferromagnetically coupled MgO/CoFe/W/CoFe/MgO structure. According to k-space and band-decomposed charge-density analyses, this oscillation can be elucidated with quantum well states on spin-up states near Fermi energy within W layers. Thus, the correlation between PMA and IEC is explained by quantum well states. These findings provide comprehensive understanding of PMA and IEC in double-interface structures and pave a new way to modulate PMA with quantum well states in heavy metal layers.

3d Metal Doping of Core@Shell Wüstite@ferrite Nanoparticles as a Promising Route toward Room Temperature Exchange Bias Magnets

“…On the other hand, the capability of interface engineering developed in the last decades offers a powerful tool for physical properties control in nanomaterials. [12,13] For example, the tuning of the interface's chemical composition to modify the surface energy level, has proven to be an effective strategy to attain a final system with tailored chemical-physical properties. [14][15][16][17][18][19] In this respect, Fe 1−x O@Fe 3 O 4 CS nanocrystals , [20][21][22] offer the possibility to modify their structural and physical properties by tuning the chemical composition by replacing Fe (II) in the RS and S systems with other divalent cations, such as Zn (II) ,Ni (II) , Mn (II) , or Co (II) .…”

Room-Temperature van der Waals Perpendicular Ferromagnet Through Interlayer Magnetic Coupling

“…where J ij is the IEC between the Co spin at site j, S j Co , and the Fe spin at site i, S i Fe . Although the interaction between PMA and IEC remains unclear in the Co/Pt/FGT trilayer [15,16], the PMA can be observed from a magnetic hysteresis loop [inset of Fig. 1(d)].…”