Ferromagnetic resonance and control of magnetic anisotropy by epitaxial strain in the ferromagnetic semiconductor (Ga0.8,Fe0.2

We study the strain dependence of the magnetic anisotropy of room-temperature ferromagnetic semiconductor $(\mathrm{G}{\mathrm{a}}_{1\ensuremath{-}x},\mathrm{F}{\mathrm{e}}_{x})\mathrm{Sb}$ ($x=20%$) thin films epitaxially grown on different buffer layers, using ferromagnetic resonance measurements. We show that the magnetocrystalline anisotropy $({K}_{\mathrm{i}})$ in $(\mathrm{G}{\mathrm{a}}_{0.8},\mathrm{F}{\mathrm{e}}_{0.2})\mathrm{Sb}$ exhibits a dependence on the epitaxial strain and changes its sign from negative (in-plane magnetization easy axis) to positive (perpendicular magnetization easy axis), when the strain is changed from tensile to compressive. Meanwhile, the shape anisotropy (${K}_{\mathrm{sh}}$) is negative and dominant over ${K}_{\mathrm{i}}$. Therefore, the effective magnetic anisotropy $({K}_{\mathrm{eff}}={K}_{\mathrm{i}}+{K}_{\mathrm{sh}})$ is always negative, leading to the in-plane magnetic anisotropy in all the $(\mathrm{G}{\mathrm{a}}_{0.8},\mathrm{F}{\mathrm{e}}_{0.2})\mathrm{Sb}$ samples. This work demonstrates ferromagnetic resonance and strong shape anisotropy at room temperature in III-V ferromagnetic semiconductors. We also observed very high Curie temperature $({T}_{\mathrm{C}}\ensuremath{\gtrsim}400\phantom{\rule{0.16em}{0ex}}\mathrm{K})$ in $p$-type (Ga,Fe)Sb, which is the highest ${T}_{\mathrm{C}}$ reported so far in III-V based ferromagnetic semiconductors.