Enhanced ferromagnetism and spin-polarized tunneling studies in Co-Mn alloy films

Abstract

Enhanced ferromagnetism is observed for extended alloy compositions in ${\mathrm{Co}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}$ $(x=0.1--0.7)$ films grown in ultraclean conditions at liquid nitrogen temperature. For these alloys, high values of spin polarization were also measured using the Meservey-Tedrow technique of spin-polarized tunneling. Ferromagnetic behavior exists even in ${\mathrm{Co}}_{0.3}{\mathrm{Mn}}_{0.7}$ alloy films, where earlier bulk studies show only antiferromagnetic behavior for alloy compositions with $x>0.3.$ X-ray diffraction and transmission electron microscopy data show a metastable fcc phase for our films, which is likely responsible for the enhanced magnetic moment. Our work shows the importance of the local environment of Mn, which is expected to dictate the magnetic interactions in these alloys.