Magnetism in small bimetallic Mn-Co clusters

Abstract

Effects of alloying on the electronic and magnetic properties of ${\text{Mn}}_{x}{\text{Co}}_{y}$ $(x+y=n=2\ensuremath{-}5;\text{ }\text{ }x=0\ensuremath{-}n)$ and ${\text{Mn}}_{2}{\text{Co}}_{11}$ nanoalloy clusters are investigated using the density-functional theory. Unlike the bulk alloy, the Co-rich clusters are found to be ferromagnetic and the magnetic moment increases with Mn concentration and is larger than the moment of pure ${\text{Co}}_{n}$ clusters of same size. For a particular sized cluster the magnetic moment increases by $2{\ensuremath{\mu}}_{B}/\text{Mn}$-substitution, which is found to be independent of the size and composition. All these results are in good agreement with recent Stern-Gerlach experiments [Phys. Rev. B 75, 014401 (2007) and Phys. Rev. Lett. 98, 113401 (2007)]. Likewise in bulk ${\text{Mn}}_{x}{\text{Co}}_{1\ensuremath{-}x}$ alloy, the local Co moment decreases with increasing Mn concentration.