Magnetic anomaly in superconducting FeSe

Synthesis, electrical and magnetic characterization of a superconducting FeSe0.85 compound is reported. An anomaly in the magnetization against temperature around 90 K is observed. The magnetic characterization of a commercial compound with nominal FeSe stoichiometry is also presented. The overall magnetic behaviors as well as the magnetic anomaly in both compounds are discussed in terms of magnetic impurities and secondary phases.