The Magnetic Properties of Iron Selenide Single Crystals

Large single crystals of Fe 7 Se 8 and Fe 3 Se 4 were prepared, and their magnetic properties below the Curie point were investigated by a torque magneto meter. The results obtained on Fe 7 Se 8 at room temperature show similar characterics to that of natural pyrhotite (Fe 7 S 8 ), i.e. the crystals can be magnetized only in the c -plane. As the temperature is lowered, however, the c -axis becomes the direction of easy magnetization. This change in direction seems to occur gradually. In the case of Fe 3 Se 4 , such a change in direction of easy magnetization does not take place. The obtained saturation magnetizations for Fe 7 Se 8 and Fe 3 Se 4 are respectively 68 and 80 gauss at the liquid air temperature.