Antiferromagnetic order in epitaxial FeSe films on SrTiO3
  Single monolayer FeSe film grown on Nb-doped SrTiO$_3$(001) substrate shows the highest superconducting transition temperature (T$_C$ $\sim$ 100 K) among the iron-based superconductors (iron-pnictide), while T$_C$ of bulk FeSe is only $\sim$ 8 K. Antiferromagnetic spin fluctuations were believed to be crucial in iron-pnictides, which has inspired several proposals to understand the FeSe/SrTiO$_3$ system. Although bulk FeSe does not show the antiferromagnetic order, calculations suggest that the parent FeSe/SrTiO$_3$ films are AFM. Experimentally, due to lacking of direct probe, the magnetic state of FeSe/SrTiO$_3$ films remains mysterious. Here, we report the direct evidences of the antiferromagnetic order in the parent FeSe/SrTiO$_3$ films by the magnetic exchange bias effect measurements. The phase transition temperature is $\geq$ 140 K for single monolayer film. The AFM order disappears after electron doping. 
Y. Zhou, L. Miao, P. Wang, F. F. Zhu, W. X. Jiang, S. W. Jiang, Y.   Zhang, H. F. Ding, H. Zheng, J. F. Jia, D. Qian and D. Wu
cond-mat.supr-con cond-mat.str-el