Half-metallicity and Gilbert damping constant in Co2FexMn1−xSi Heusler alloys depending on the film composition

Transport properties in magnetic tunnel junctions (MTJs) with ${\text{Co}}_2{\text{Fe}}_x{\text{Mn}}_{1-x}\text{Si}$ $\left(\text{CFMS},x=0–1.0\right)/\text{Al}–\text{O}/{\text{Co}}_{75}{\text{Fe}}_{25}$ structure and Gilbert damping constant in the epitaxial CFMS films were investigated. The tunnel magnetoresistance ratio is as high as 75% in MTJs with $x=0.6$ at room temperature. The Gilbert damping constant is minimal at $x=0.4$ . Relations between half-metallicity and the Gilbert damping constant in CFMS films were examined, revealing that the damping constant is small in half-metallic CFMS films.