Ultrathin copper films grown on SrTiO3 substrates for epitaxy of single-crystalline γ-FeMn

The topological antiferromagnet γ-FeMn is a fascinating material for studying unconventional magnetic properties and topological transport phenomena though high-quality γ-FeMn has been obtained on the Cu substrate for magnetic research. However, the difficulty of growing single-crystalline γ-FeMn films on insulating substrates has prevented experiments from exactly verifying many theoretical predictions on their transport properties. Ultrathin Cu buffer films have been considered for solving this problem but failed because the crystal quality and thickness of Cu films achieved in previous works do not satisfy the growth buffer criteria for γ-FeMn. In this work, the growth of 5-nm-thick Cu films on SrTiO3(001) substrates was studied. It was found that single-crystalline ultrathin Cu films with roughness as low as 1 nm are obtained on the insulating substrate. We subsequently obtained high crystalline quality γ-FeMn films with smooth surface and verified their antiferromagnetism. Finally, two aspects of the influence of Cu films on adjacent films have been analyzed. Our results facilitate the experimental exploration of the fascinating properties of γ-FeMn.