Giant tunneling magnetoresistance based on spin-valley-mismatched ferromagnetic metals

Abstract

Half metals, which are amenable to perfect spin filtering, can be utilized for high-magnetoresistive devices. However, available half metals are very limited. Here, we demonstrate that materials with intrinsic spin-valley-mismatched (SVM) states can be used to block charge transport, resembling half metals and leading to giant tunneling magnetoresistance. As an example, by using first-principles transport calculations, we show that ferromagnetic 1\emph{T}-VSe$_2$, 1\emph{T}-VS$_2$, and 2\emph{H}-VS$_2$ are such spin-valley-mismatched metals, and giant magnetoresistance of more than 99\% can be realized in spin-valve van der Waals (vdW) junctions using these metals as electrodes. Owing to the intrinsic mismatch of spin states, the central-layer materials for the vdW junctions can be arbitrary nonmagnetic materials, in principle. Our research provides clear physical insights into the mechanism for high magnetoresistance and opens new avenues for the search and design of high-magnetoresistance devices.

Figures (4)

• Figure 1: Comparison of transmission under the AP configuration for using (a) half metals, (b) normal FM metals, and (c) SVM FM metals as the leads using spin-resolved density of states (upper panels) and Brillouin zones (lower panels). Shaded areas stand for occupied states. In (a), transport of electrons is prohibited due to spin mismatch of charge carriers. In (b), the charge carriers are allowed to transport. By contrast, the transport between same-spin states is not allowed in (c) due to the mismatch of $\bf{k}$ vectors. (d) Based on the observations in (c), FM/Spacer/FM junctions using SVM FM metals may exhibit high MR.
• Figure 2: (a) Top view and (b) side view of the crystalline structure of 1$T$-VSe$_2$. (c) Band structure and (d) the L/C/R model used for calculating transport properties of VSe$_2$-based magnetic tunneling junctions. Here, VSe$_2$/1-MoSe$_2$/VSe$_2$ is shown as an example. The system is infinite along the $z$ direction, and periodic along the $x$ and $y$ directions. (e) Spin-up (left panel) and spin-down (right panel) transporting channels of bulk VSe$_2$ illustrated in the first Brillouin Zone. Yellow color indicates the existence of transporting channels.
• Figure 3: Zero-bias transport properties of the VSe$_2$/1-MoSe$_2$/VSe$_2$ junction. (a) spin-up and (b) spin-down transmission spectra under the P configuration and (c) spin-up/down transmission spectrum under the AP configuration. Transmission coefficients as a function of energy for spin-up (blue solid line) and spin-down (red dash line) electrons at zero bias under (d) P and (e) AP configurations.
• Figure 4: Transport properties of the VSe$_2$/1-MoSe$_2$/VSe$_2$ junction under a bias voltage. (a) Spin-up (blue solid line), spin-down (red dash line) current densities under the P configuration, and total current densities under the P (red solid line with empty circles) and AP (black line with filled circles) configurations. (b) MR$_o$ (left) and MR$_p$ (right) as a function of bias voltage. (c-d) Contour plot of the spin-up and spin-down transmission coefficients as functions of energy and bias under the P configuration. The black dash line and the white dash line indicate the bias window.