Observation of superconducting and ferromagnetic states coexisting in Bi2Se3-doped FeSe crystals

Bi2Se3-doped FeSe crystals were synthesized from self-flux method. The crystalline, morphological, transport and magnetization properties have been investigated. The obtained samples have mix structures of hexagonal and tetragonal phases. The ratio of the tetragonal phase and the superconducting transition temperature increased with increasing doping content when the dopant concentration was low, and then decreased at higher dopant concentration. Superconducting phase coexisting with ferromagnetic phase were found in all samples.