Air-stable tetragonal antiferromagnetic FeTe thin films by molecular beam epitaxy

Antiferromagnetic (AFM) materials have gained renewed attention due to recent demonstration of manipulation and detection of the magnetic state of antiferromagnets. Here we report thin film growth of AFM tetragonal FeTe on SrTiO₃(001) substrates by molecular beam epitaxy (MBE). Layer-by-layer growth is verified by in situ scanning tunneling microscopy (STM), and atomic resolution imaging displays square lattices, confirming the tetragonal phase. Furthermore, tunneling spectroscopy shows metallic behavior. For Se-capped 20 monolayer FeTe films, temperature-dependent superconducting quantum interference device (SQUID) magnetometry measurements indicate the Néel temperature (T_N) of about 100 K.  The T_N drops to 75 K after air exposure for more than a year. Electrical transport measurements reveal that majority carriers are p-type, and that the system is metallic from room temperature down to 2 K. The carrier mobility reaches >2,000 cm²/V∙s at 2 K, three orders of magnitude higher than those previously reported in this material system. The growth of high-quality wafer-scale air-stable AFM FeTe thin films opens new opportunities for studies of novel phenomena for spintronic applications.