Influence of film composition in Co2MnSi electrodes on tunnel magnetoresistance characteristics of Co2MnSi/MgO/Co2MnSi magnetic tunnel junctions

Fully epitaxial Co2MnSi (CMS)/MgO/CMS magnetic tunnel junctions (MTJs) with various values of Mn composition alpha in Co2Mn alpha Si electrodes were fabricated and the influence of alpha on the tunnel magnetoresistance (TMR) characteristics of these MTJs was investigated. MTJs with Mn-rich CMS electrodes showed TMR ratios, up to 1135% at 4.2 K and 236% at room temperature for alpha = 1.29, exceeding those of MTJs with CMS electrodes having an almost stoichiometric composition. A possible origin of the higher TMR ratios for alpha beyond 1.0 is a decreased density of gap states existing around the Fermi level in the half-metal gap caused by the suppression of Co-Mn antisites, where a Mn site is replaced by a Co atom, for Mn-rich CMS electrodes. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3272926]