Structural and Magnetic Properties of Co2MnSi Thin Film with a Low Damping Constant**Supported by the National Basic Research Program of China under Grant No 2015CB921502, the National Natural Science Foundation of China under Grant Nos 11474184 and 11174183, the 111 Project under Grant No B13029, the Natural Science Foundation of Shandong Province under Grant No JQ201201, the Doctorate Foundation of

Abstract

Co2MnSi thin films are made by magnetron sputtering onto MgO (001) substrates. The crystalline quality is improved by increasing depositing temperature and/or annealing temperature. The sample deposited at 550°C and subsequently annealed at 550°C (sample I) exhibits a pseudo-epitaxial growth with partially ordered L21 phase. Sample I shows a four-fold magnetic anisotropy, in addition to a relatively weak uniaxial anisotropy. The Gilbert damping factor of sample I is smaller than 0.001, much smaller than reported ones. The possible reasons responsible for the small Gilbert damping factor are discussed, including weak spin-orbit coupling, small density of states at Fermi level, and so on.