Magnetic field induced room temperature spin nematicity in tetragonal antiferromagnetic FeTe thin films grown by molecular beam epitaxy

Iron chalcogenide FeTe is the parent compound of superconducting iron chalcogenides. It exhibits a spontaneous double-stripe bicollinear antiferromagnetic (AFM) order whose Néel temperature (T_N) coincides with the temperature of a structural transition from tetragonal to monoclinic lattice distortion. For bulk materials, recent in-plane angular-dependent magnetoresistance measurement has further revealed a magnetic-?eld-induced spin nematicity at 110 K, above the antiferromagnetic ordering T_N. In this work, we report similar spin-nematicity in epitaxial FeTe thin films, which persists up to room temperature. The FeTe films were grown on SrTiO₃(001) substrates by molecular beam epitaxy, which exhibits a layer-by-layer growth as verified by in-situ scanning tunneling microscopy. The AFM order is confirmed by superconducting quantum interference device magnetometry with a T_N of 75 K. Transport measurements indicate p-type carrier from room temperature to 2 K with a mobility of 2,162 cm²/V·s at low temperature, which is three orders of magnitude higher than those previously reported in this material system. Anisotropic magnetoresistance measurements reveal a two-fold anisotropy under rotating in-plane magnetic fields up to 9 T. The anisotropy persists up to room temperature, indicating magnetic field induced spin nematicity above T_N.