Giant magnetoresistance in spin valves realized by substituting Y-site atoms in Heusler lattice

Abstract

"All-Heusler'' spin-valve constructed by two half-metallic Heusler electrodes and a non-magnetic Heusler spacer contains two interfaces that have a crucial influence on the magnetoresistance. In order to reduce the disorder at the interface and protect the half metallicity of the electrode at the same region, we propose a scheme to construct a spin valve by replacing the Y-site atoms in the half-metallic Heusler electrode to obtain the corresponding non-magnetic spacer based on the Slater-Pauling rule. In this way, the lattice and band match of the two materials can be ensured naturally. By using Co2FeAl as electrode and Co2ScAl as the spacer materials, we construct the Co2FeAl/Co2ScAl/Co2FeAl(001)-spin valve. Based on the first-principles calculation, the most stable FeAl/CoCo-interface is determined both from the phonon spectra and the formation energy when the spacer Co2ScAl grows on the FeAl-terminated (001) surface of electrode material Co2FeAl. By comparing the projected density of states of the interfacial atoms with the corresponding density of states of the bulk electrode material, only the value of spin-up state of Al changes from 0.17 states/atom/eV to 0.06 states/atom/eV before and after substitution, the half metallicity at the interface is maintained. As a result, the spin-dependent transport properties show significant theoretical magnetoresistance MRop which can reach up to 1010% and much larger than 106% reported before.

Spin filters based on two-dimensional materials Co2Si and Cu2Si

“…As shown in the top panel of figure 2, the transport direction is defined as z direction, and the central Co 2 Si strip of the device model Cu 2 Si/Co 2 Si/Cu 2 Si can be understood as the Cu atoms in 2D Cu 2 Si plane replaced by Co atoms. Actually, such an atom replacement is very likely to be implemented under certain experimental circumstance [50]. It should be pointed out that the device is repeated in x direction indefinitely, moreover, the left/right electrode is repeated in negative/positive z direction to semi-infinite one.…”

Effect of off-stoichiometric composition on half-metallic character of Co2Fe(Ga,Ge) investigated using saturation magnetization and giant magnetoresistance effect

“…Magneto-resistive (MR) devices with low device resistance and a high output signal are indispensable for use as read sensors in next-generation hard disk drives [1]. A currentperpendicular-to-plane (CPP) giant magnetoresistance (GMR) device using Co-based Heusler alloy (Co 2 YZ, where Y is usually a transition metal and Z is a main group element) is a promising candidate for such devices [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. This is because many Co-based Heusler alloys, such as Co 2 MnSi (CMS) and Co 2 MnGe (CMG), have theoretically 100% spin polarization at Fermi level (E F ) due to their half-metallic nature, which is characterized by an energy gap for one spin direction at E F [18][19][20][21][22].…”