Electronic structure and magnetic exchange coupling in ferromagnetic full Heusler alloys

Abstract

Density-functional studies of the electronic structures and exchange interaction parameters have been performed for a series of ferromagnetic full Heusler alloys of general formula ${\mathrm{Co}}_{2}\mathrm{Mn}Z$ $(Z=\mathrm{Ga},\mathrm{Si},\mathrm{Ge},\mathrm{Sn})$, ${\mathrm{Rh}}_{2}\mathrm{Mn}Z$ $(Z=\mathrm{Ge},\mathrm{Sn},\mathrm{Pb})$, ${\mathrm{Ni}}_{2}\mathrm{Mn}\mathrm{Sn}$, ${\mathrm{Cu}}_{2}\mathrm{Mn}\mathrm{Sn}$, and ${\mathrm{Pd}}_{2}\mathrm{Mn}\mathrm{Sn}$, and the connection between the electronic spectra and the magnetic interactions have been studied. Different mechanisms contributing to the exchange coupling are revealed. The band dependence of the exchange parameters, their dependence on volume and valence electron concentration have been thoroughly analyzed within the Green function technique. The difference between the exact adiabatic approach and the long-wavelength approximation is discussed.