Helical Spin Arrangement in Cubic FeGe

The magnetic properties of single crystals of the cubic B20 modification of the metallic compound FeGe have been investigated by means of a vibrating-sample magnetometer and a torsion balance. Transition to an ordered spin structure occurs at 280 K. Magnetization curves below this temperature shown an almost linear field dependence for the [100], [111] directions with a field of about 2 kOe required for saturation at low temperatures, indicating a small magnetocrystalline energy compared to the exchange energy. The saturation moment as extrapolated to zero Kelvin corresponds to 1.0μ B . A model with the spins forming a helical screw propagating in the [111] direction at zero field is proposed to explain the observed magnetic properties.