{"content"=>"Spin injection and magnetoresistance in MoS-based tunnel junctions using FeSi Heusler alloy electrodes.", "sub"=>[{"content"=>"2"}, {"content"=>"3"}]} (original) (raw)
Related papers
Scientific Reports, 2018
Recently magnetic tunnel junctions using two-dimensional MoS 2 as nonmagnetic spacer have been fabricated, although their magnetoresistance has been reported to be quite low. This may be attributed to the use of permalloy electrodes, injecting current with a relatively small spin polarization. Here we evaluate the performance of MoS 2-based tunnel junctions using Fe 3 Si Heusler alloy electrodes. Density functional theory and the non-equilibrium Green's function method are used to investigate the spin injection efficiency (SIE) and the magnetoresistance (MR) ratio as a function of the MoS 2 thickness. We find a maximum MR of ~300% with a SIE of about 80% for spacers comprising between 3 and 5 MoS 2 monolayers. Most importantly, both the SIE and the MR remain robust at finite bias, namely MR > 100% and SIE > 50% at 0.7 V. Our proposed materials stack thus demonstrates the possibility of developing a new generation of performing magnetic tunnel junctions with layered two-dimensional compounds as spacers.
IEEE Transactions on Magnetics, 2000
Transport, as well as chemical and magnetic interface properties of two kinds of magnetic tunnel junctions (MTJs) with Co 2 FeSi electrode, Al-O barrier, and Co-Fe counter electrode, are investigated. For junctions with Co 2 FeSi single-layer electrodes, a tunnel magnetoresistance of up to 52% is found after optimal annealing for an optimal Al thickness of 1.5 nm, whereas the room temperature bulk magnetization of the Co 2 FeSi film reaches only 75% of the expected value. By using a [Co 2 MnSi/Co 2 FeSi] 10 multilayer electrode, the magnetoresistance can be increased to 114%, corresponding to a large spin polarization of 0.74, and the full bulk magnetization is reached. For Al thickness smaller than 1 nm, the TMR of both kinds of MTJs decreases rapidly to zero. On the other hand, for 2-to 3-nm-thick Al, the TMR decreases only slowly. The Al thickness dependence of the TMR is directly correlated to the element-specific magnetic moments of Fe and Co at the Co 2 FeSi/Al-O interface for all Al thickness. Especially, for optimal Al thickness and annealing, the interfacial Fe moment of the single-layer electrode is about 20% smaller than for the multilayer electrode, indicating smaller atomic disorder at the barrier interface for the latter MTJ.
Physical Review B, 1998
Based on the two-band model and free-electron approximation, magnetism and transport properties of magnetic tunnel junctions with nonmagnetic metallic ͑NM͒ spacers and finite thick ferromagnetic ͑FM͒ layers are studied. The mean conductance and tunnel magnetoresistance are oscillatory functions of NM and FM thicknesses, their period is determined by the Fermi-surface properties of the metals, and magnetoresistances (ϳ10 3 %) much greater than those predicted by Julliere's model are obtained. The oscillation of interlayer exchange coupling with metal layer thickness that originates from the interference of electron waves at different energy levels is found in contrast with the situation in metallic magnetic multilayers. Our results indicate that giant tunnel magnetoresistances with weak antiferromagnetic coupling can be attained by controlling the metal layer thickness, and this has potential in designing spin-polarized tunneling devices.
Co 2 MnSi as full Heusler alloy ferromagnetic electrode in magnetic tunneling junctions
physica status solidi c, 2006
The discoveries of antiferromagnetic coupling in Fe/Cr multilayers by Grünberg, the Giant MagnetoResistance by Fert and Grünberg and a large tunneling magnetoresistance at room temperature by Moodera have triggered enormous research on magnetic thin films and magnetoelectronic devices. Large opportunities are especially opened by the spin dependent tunneling resistance, where a strong dependence of the tunneling current on an external magnetic field can be found. In order to obtain large magnetoresistance effects, materials with strongly spin polarized electron gas around the Fermi level have to be found. New materials with potentially 100% spin polarization will be discussed using the example of the full Heusler compound Co 2 MnSi. First, experimental aspects of the integration of this alloy in magnetic tunneling junctions will be addressed. With these junctions, we obtain up to 100% TMR at low temperature. The current status of this research will then be summarized with special regard to the complex diffusion mechanisms occurring in these devices and to the properties of the interfaces between the Heusler material and the insulator.
Computational Materials Science, 2022
In this work, employing density functional theory based electronic structure calculations, we search for an alternative to MgO as a spacer layer in a magnetic tunneling junction(MTJ), with half-metallic(HM) Co 2 MnSb as an electrode. First, we demonstrate the possibility of designing an all-Heusler alloy based MTJ with semiconducting(SC) TiCoSb alloy as the spacer material. We probe the robustness of the HM properties of the Mn-Sb/Co interface and show that the HM property is preserved, even with various disorders and defects. The spin-dependent transport behavior indicates that these properties depend sensitively on the heterojunction interfaces and thickness of the spacer material. Further, we study the transport properties of the heterojunctions of Co 2 MnSb alloy with the well-studied insulator MgO as well as the less-explored systems like, NaCl and AlN. In these three insulating materials, the smallest complex band decay coefficient is associated with 1 symmetry, unlike TiCoSb. This feature enables more desirable symmetry-based spin-filtering properties at the point in the 2D Brillouin zone. We further calculate the resistance area (RA) product for all the heterojunctions, important for the realization of highly sensitive magnetic sensors and it is found that the other spacer layers yield a RA product, several orders less in magnitude compared to that of TiCoSb. Our results indicate that NaCl and AlN may be promising as an alternative to MgO as a spacer material. With the chemical compatibilities resulting into minimal interface buckling and an ultra-low RA product, TiCoSb may also be a promising new material for a MTJ with Co 2 MnSb as electrode, specifically in relation to overcoming the variability and current-injection challenges.
Magnetic tunnel junctions with an equiatomic quaternary CoFeMnSi Heusler alloy electrode
Applied Physics Letters, 2018
Tunnel magnetoresistance (TMR) in MgO-based magnetic tunnel junctions (MTJs) with equiatomic quaternary CoFeMnSi Heusler and CoFe alloy electrodes is studied. The epitaxial MTJ stacking structures were prepared using ultrahigh-vacuum magnetron sputtering, where the CoFeMnSi electrode has a full B2 and partial L21 ordering crystal structure. Maximum TMR ratios of 101% and 521% were observed at room temperature and 10 K, respectively, for the MTJs. The large bias voltage dependence of the TMR ratio was also observed at low temperature (LT), as similarly observed in Co2MnSi Heusler alloy-based MTJs in the past. The physical origins of this relatively large TMR ratio at LT were discussed in terms of the half-metallicity of CoFeMnSi.
IEEE Transactions on Magnetics, 2013
Magnetic tunnel junctions with Fe1+xCo2−xSi (0 ≤ x ≤ 1) electrodes and MgO barrier were prepared on MgO substrates by magnetron co-sputtering. Maximum tunnel magnetoresistance (TMR) ratios of 262% at 15 K and 159% at room temperature were observed for x = 0.75. Correlations of the annealing temperature dependent atomic ordering and TMR amplitude are discussed. The high TMR for an intermediate stoichiometry is ascribed to the adjustment of the Fermi energy within a minority spin pseudo gap.