Theoretical study on spintronic and spin caloritronic applications for equiatomic quaternary Heusler alloy NiCoMnAl

Abstract

Equiatomic quaternary Heusler alloys (EQHAs) have received more and more attention in spintronic applications due to the half-metallicity and the long spin diffusion length. Recently, nearly half-metallicity (nearly 100% electronic spin polarization) and high Curie temperature (above 583 K) have been found in the equiatomic quaternary Heusler alloy of NiCoMnAl. In order to explore the potential spintronic applications, in this work, we design the magnetic tunnel junction (MTJ) of NiCoMnAl/InP/NiCoMnAl(0 0 1), and theoretically investigate the spin transport properties. It is shown that the MTJ exhibits a spin filtering effect and a high tunnel magnetoresistance ratio (up to 1.4 × 107%) when a bias voltage is applied to the electrodes of NiCoMnAl. Interestingly, without a bias voltage, a temperature difference can also drive the spin filtering effect. These versatile transport properties are discussed in terms of the half-metallicity of electrode, the spin-polarized transmission spectrum, and the difference of Fermi–Dirac distribution. The present work indicates promising applications for NiCoMnAl in spintronic devices and spin caloritronic devices.