Extremely Large Non-equilibrium Tunnel Magnetoresistance Ratio in CoRhMnGe Based Magnetic Tunnel Junction by Interface Modification

Abstract

Equiatomic quaternary Heusler compounds (EQHCs) generally have the advantages of high Curie temperature, large spin polarization and long spin diffusion length, and they are regarded as one of the most promising candidates for spintronics devices. Herein, we report a theoretical investigation on an EQHC CoRhMnGe based magnetic tunnel junction (MTJ) with (i) MnGe-terminated interface and (ii) modified pure Mn terminated interface, i.e., MnMn-terminated interface. By employing first principle calculations combined with non-equilibrium Green's function, the local density of states (LDOS), transmission coefficient, spin-polarized current, tunnel magnetoresistance (TMR) ratio and spin injection efficiency (SIE) as a function of bias voltage are studied. It reveals that when the MTJ under equilibrium state, TMR ratio of MnGe-terminated structure is as high as 3,438%. When the MTJ is modified to MnMn-terminated interface, TMR ratio at equilibrium is enhanced to 2 × 10 5 %, and spin filtering effects are also strengthened. When bias voltage is applied to the MTJ, the TMR ratio of the MnGe-terminated structure suffers a dramatic loss. While the modified MnMn-terminated structure could preserve a large TMR value of 1 × 10 5 %, even bias voltage rises up to 0.1 V, showing a robust bias endurance. These excellent spin transport properties make the CoRhMnGe a promising candidate material for spintronics devices.

Quantum magnetic phenomena in engineered heterointerface of low-dimensional van der Waals and non-van der Waals materials

“…An MTJ fabricated using a heterostructure having enhanced interfacial magnetization was reported, exhibiting an enhancement in TMR value from 50% to 170%. 146,147 A higher TMR value was also reported by theoretical calculation on the heterojunction of CoRhMnGe/MgO/CoRhMnGe, 143 which revealed that the modification of interface termination from Mn-Ge to Mn-Mn in the heterojunction led to a higher TMR value of the order of 10 5 % and strong spin filter ability (as shown in Fig. 10b and c).…”

“…10b and c). 143 Moreover, the higher TMR of MTJ containing a modified interface was sustained at bias voltage, whereas this was not observed in the unmodified interface in the MTJ. This shows the advantageous possibility of interface modification in achieving robust TMR for MTJ independent of external perturbation.…”

“…Reports confirmed that spin current polarization depends on the insulating layer and achieving 100% spin polarization at the interface of engineered heterostructures is possible. 143,144 Spin polarization of the tunneling current shows an opposite sign in the heterostructure of Co/Al 2 O 3 /Co due to presence or absence of O at the Co/Al 2 O 3 interface, which shows the control of the interface on spin polarization. 145 Higher TMR values indicate high-performing MTJ.…”