Exploring stable half-metallicity and magnetism of Cr-based double half-Heusler alloys and its high magnetoresistance ratio in magnetic tunnel junction.

A new series of double half-Heusler (DHH) alloy Cr 2 FeCoZ 2 (Z = As, Ge, S, P) are investigated by using the non-equilibrium Green's function in combination with the first-principles calculations. The calculations on magnetism reveal that these Cr-based DHH alloys are ferrimagnets due to the antiparallel magnetic coupling between Cr and Fe (Co). The electronic structure calculations of the Cr-based DHH alloys reveal half-metallicity, and Cr 2 FeCoAs 2 possesses the largest spin-down gap of 1.181 eV. Within the c/a ranges from 1.60 to 2.52, Cr 2 FeCoAs 2 maintains its 100 % spin-polarization, and the changes in total and spin-resovled atomic magnetic moment are negligible, showing a stable half metallicity and magnetism against the tetragonal distortion. Futhermore, the transport properties are investigated by constructing the Cr 2 FeCoZ 2 /GaAs/Cr 2 FeCoZ 2 magnetic tunnel junction (MTJ) model. By changing the magnetic arrangement of the left and right electrodes into antiparallel configuration, the capability of transportation in both spin channels is significantly limited. Conversely, by modulating the magnetic arrangement of the left and right electrodes into parallel configuration, the transportation of electrons in spin-up channel is exceptionally strong while that of the spin-down channel is severely impeded. The Cr 2 FeCoAs 2 /GaAs/Cr 2 FeCoAs 2 MTJ owns the highest tunneling magnetoresistance (TMR) ratio of ∼7.42 × 108 %, indicating that Cr 2 FeCoAs 2 is the most promising candidate for high performance spintronic devices. • A series of Cr-based double half-Heusler alloy is confirmed to possess stable half-metallicity. • The calculated TMR ratio of the Cr 2 FeCoAs 2 /GaAs/Cr 2 FeCoAs 2 MTJ is up to ∼7.42 × 108 %. [ABSTRACT FROM AUTHOR]