Development of half metallicity within mixed magnetic phase of Cu$_{1-x}$Co$_x$MnSb alloy

TL;DR

This study explores how Co doping in CuMnSb induces a transition from antiferromagnetic to ferromagnetic phases, resulting in a nearly half-metallic state with potential spintronic applications.

Contribution

It provides experimental and theoretical evidence of a mixed magnetic phase and the emergence of half-metallicity at 10% Co doping in CuMnSb.

Findings

AFM to FM transition occurs via percolation mechanism.

Nearly half-metallic band structure develops at 10% Co doping.

Energy gap at the Fermi surface confirmed by resistivity and electronic structure calculations.

Abstract

Cubic Half-Heusler Cu$_{1-x}$Co$_x$MnSb (0 $\leq$ $x$ $\leq$ 0.1) compounds have been investigated both experimentally and theoretically for their magnetic, transport and electronic properties in search of possible half metallic antiferromagnetism. The systems (Cu,Co)MnSb are of particular interest as the end member alloys CuMnSb and CoMnSb are semi metallic (SM) antiferromagnetic (AFM) and half metallic (HM) ferromagnetic (FM), respectively. Clearly, Co-doping at the Cu-site of CuMnSb introduces changes in the carrier concentration at the Fermi level that may lead to half-metallic ground state but there remains a persistent controversy whether the AFM to FM transition occurs simultaneously. Our experimental results reveal that the AFM to FM magnetic transition occurs through a percolation mechanism where Co-substitution gradually suppresses the AFM phase and forces FM polarization around every dopant cobalt. As a result a mixed magnetic phase is realized within this composition range while a nearly HM band structure is developed already at the 10% Co-doping. Absence of T$^2$ dependence in the resistivity variation at low T-region serves as an indirect proof of opening up an energy gap at the Fermi surface in one of the spin channels. This is further corroborated by the ab-initio electronic structure calculations that suggests a nearly ferromagnetic half-metallic ground state is stabilized by Sb-p holes produced upon Co doping.