1National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China 2York-Nanjing Joint Center (YNJC) for Spintronics and Nano-Engineering, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, China 3College of Sciences, Northeastern University, Shenyang 110819, China 4School of Physics Science and Engineering, Tongji University, Shanghai 200092, China 5Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
Abstract：We investigate the structural, static magnetic and damping properties in two Mn-deficient magnetic Weyl semimetal Co-Mn-Ga (CMG) alloy films, i.e., Co$_{55}$Mn$_{18}$Ga$_{27}$ (CMG1) and Co$_{50}$Mn$_{18}$Ga$_{32}$ (CMG2), which were epitaxially grown on MgO (001) substrates. CMG1 has a mixing phase of $B_{2}$ and $L2_{1}$, larger saturation magnetization ($M_{\rm s} \sim 760$ emu/cm$^{3}$), stronger in-plane magnetic anisotropy. CMG2 has an almost pure $B2$ phase, smaller $M_{\rm s}$ ($\sim$ $330$ emu/cm$^{3}$), negligible in-plane magnetic anisotropy. Time-resolved magneto-optical Kerr effect results unambiguously demonstrate an obvious perpendicular standing spin wave (PSSW) mode in addition to the Kittel mode for both of the CMG films. The intrinsic damping constant is about 0.0055 and 0.015 for CMG1 and CMG2, respectively, which are both significantly larger than that of the stoichiometric CMG (i.e., Co$_{2}$MnGa) film reported previously. In combination with the first-principles calculations, the intrinsic damping properties of the Mn-deficient CMG films can be well explained by considering the increase of density of states at the Fermi level, reduction of $M_{\rm s}$, and excitation of the PSSW mode. These findings provide a new clue to tuning the magnetic damping of the magnetic Weyl semimetal film through slight off-stoichiometry.
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2023, Vol. 40 
