High spin polarization in quaternary Heusler Fe–Rh–Mn–Al alloys

Abstract

In this theoretical study, we investigate novel quaternary Heusler Fe–Rh–Mn–Al alloys in the X-type structure with different types of atomic ordering in the unit cell within the spin-polarized density functional calculations. The calculations showed that the 24 possible configurations converge to the 6 nonequivalent solutions. Two types of atomic ordering with the lowest total energy Fe(4c)Rh(4d)Al(4b)Mn(4a) and Mn(4c)Al(4d)Fe(4b)Rh(4a) are half-metallic ferrimagnets in which the spin polarization at the Fermi level is close to 100 %. However, no gap is open in the majority spin projection. The following values of the total magnetic moments for these alloys were obtained: 3.01 and 3.19 μB/f.u., respectively. In the other types of atomic ordering, the half-metallic state is not formed. In FeAlRhMn, the magnetic moment on the manganese ion compensates for the moments on the other ions, and the total moment is close to zero. In the types (MnFeRhAl, AlRhFeMn) of atomic ordering with high energies, the metallic state is also realized, and the magnetic moments on the ions are ordered ferrimagnetically. In this work, we analyzed novel quaternary alloys with different types of atomic ordering motivated by the demand for alloys with a high spin polarization, among which the FeRhAlMn and MnAlFeRh alloys were found. Both with a half-metallic ferrimagnetic state and the lowest total energy among these alloys with the same chemical composition, which indicates the stability of the half-metallic state. The other types of atomic ordering are less energetically favorable, those alloys are ferrimagnetic metals with the low spin polarization. Taking into account the half-metallic state and high spin polarization, the quaternary FeRhAlMn and MnAlFeRh alloys have prospects for use in spintronic devices.