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 × 105%, 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 × 105%, 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.
Highlights
Spintronics, with the manipulation of electron spin as information carrier, has the advantages of higher circuit integration density, fast operation and less energy consumption (Wolf et al, 2001; Žuticet al., 2004; Li and Yang, 2016)
Our results show that CoRhMnGe/MgO/CoRhMnGe magnetic tunnel junction (MTJ) possess extremely large tunnel magnetoresistance (TMR) value, and such value could be further enhanced when the interface of the MTJ is modified to Mn-rich termination
The transmission coefficient vs. electron energy for MnGe-terminated and MnMn-terminated structures at equilibrium are calculated and displayed in Figure 2. (i) When two magnetic electrodes are in antiparallel magnetization configuration (APC), due to the reason that these two structures are mirror-symmetrical with respect to the middle of the scattering region, the transmission coefficient curve in spin up channel completely coincide with that in spin down channel
Summary
Spintronics, with the manipulation of electron spin as information carrier, has the advantages of higher circuit integration density, fast operation and less energy consumption (Wolf et al, 2001; Žuticet al., 2004; Li and Yang, 2016). As one of the most important spintronic devices, magnetic tunnel junction (MTJ), consisting of two ferromagnetic (FM) electrodes separated by a thin non-magnetic (NM) semiconductor layer, has attracted great attention (Li et al, 2014; Iqbal et al, 2016; Wang et al, 2016a). Β is determined by the electronic band structure of FM layers, half-metallic ferromagnet (HMF) which owns complete spin polarization has been regarded as one of the most promising materials to work as electrode (Wen et al, 2014; Feng et al, 2019). The equiatomic quaternary Heusler compound CoRhMnGe has been successfully synthesized (Rani et al, 2017) It demonstrates half metallicity with high Curie temperature of ∼760 K, revealing great potential for spintronic devices.
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