Neutron diffraction study of single crystal europium in an applied magnetic field

A single crystal of europium has been studied in applied magnetic fields up to 41.7 koe. At T_N = 90.5 ± 0.5°K a first order magnetic transition is observed. At 4.2°K the effect of an applied magnetic field in either a 〈100〉 or 〈110〉 direction is to stabilize a helix structure having τ along the field direction. This field stabilized structure remains even if the field is reduced to zero. The hysteresis associated with these transformations has been investigated and is discussed. No ferromagnetic components have been detected in fields up to 41.7 koe.