Effects of Interfacial Termination, Oxidation, and Film Thickness on the Magnetic Anisotropy in Mn_2.25Co_0.75Ga_0.5Sn_0.5/MgO Heterostructures

Abstract

Perpendicular magnetic anisotropy (PMA) is a determining factor for the realization of nonvolatile information storage devices with high efficiency and thermal stability. In this work, a new spin gapless semiconductor Mn2.25Co0.75Ga0.5Sn0.5 Heusler alloy with an inter-spin zero gap was first designed theoretically. The Mn2.25Co0.75Ga0.5Sn0.5 bulk was prepared successfully in experiment. The effects of interfacial termination, oxidation, and film thickness on the magnetic anisotropy of Mn2.25Co0.75Ga0.5Sn0.5/MgO (MCGS/MgO) heterostructures are investigated systematically by first-principles calculations. The results show that all the Mn­(A)­Mn­(C)­GaSn-, Mn­(A)­Mn­(C)­CoGaSn-, Mn­(B)­GaSnI-, and Mn­(B)­GaSnII-terminated MCGS/MgO heterostructures (called as AC1, AC2, BD1, and BD2 models, respectively) present PMA, which mainly derives from the interfacial and surficial MCGS layers. Furthermore, the PMA of MCGS/MgO heterostructures can be preserved in a large range of interfacial oxidization (up to ±50%). With MCGS thickness increasing from 5 to 16 monolayers, the PMA of MCGS/MgO heterostructures with an AC-type surface decreases significantly. However, the PMA of BD-type surface models is relatively robust to the thickness of the MCGS layer, and the magnetic anisotropy always points to the out-of-plane direction. Therefore, MCGS Heusler alloy is a new promising spin gapless semiconductor candidate for spintronics applications. The robust and tunable PMA in MCGS/MgO heterostructures offers the possibility for developing nonvolatile data memory devices.

Theoretical scheme of nonvolatile strain-switchable high/low resistance based on novel strain-tunable magnetic anisotropy in the Mn2.25Co0.75Ga0.5Sn0.5/MgO superlattice

“…In other words, the majority-spin valence band and the minority-spin conduction band have an indirect inter-spin zero gap for MCGS around the Fermi level, indicating the spin gapless semiconducting behavior. Therefore, MCGS is a SGS material, which is consistant with our previous study 26 and is similar to previous reports on Mn 2 CoAl. 41,42 In addition, MCGS is ferrimagnetic and has a magnetic moment of 2 μ B per unit cell.…”

“…where a 0 and a are the in-plane lattice constants of the equilibrium and strained (MCGS) 2 /(MgO) 1 superlattice, respectively. Therefore, MCGS is a SGS material, which is consistant with our previous study 26 and is similar to previous reports on Mn 2 CoAl. 41,42 In addition, MCGS is ferrimagnetic and has a magnetic moment of 2m B per unit cell.…”

“…In this work, we investigate the electronic and magnetic properties of (Mn 2.25 Co 0.75 Ga 0.5 Sn 0.5 ) 2 /(MgO) 1 superlattices, and the strain-tunable band structure and magnetic anisotropy energy (MAE) are explored using first-principles calculations, in which the Heusler alloy Mn 2.25 Co 0.75 Ga 0.5 Sn 0.5 (MCGS) was predicted to be a promising spin gapless semiconductor (SGS) candidate. 26 We predict that (MCGS) 2 /(MgO) 1 superlattices with three different interfaces, Mn(A)CoGaSn-, Mn(A)Mn(C)CoGaSn- and Mn(B)CaSn-terminated interfaces (labeled as AC1, AC2 and BD models, respectively), present PMA. Remarkably, the MAE in the most energy-stable AC2 model is very sensitive to the extrinsic interfacial strain.…”