Kagome staircase compound Co3V2O8 in an applied magnetic field: Single-crystal neutron diffraction study

The magnetic properties of Co3V2O8 have been studied by single-crystal neutron diffraction. In zero magnetic field, the observed broadening of the magnetic Bragg peaks suggests the presence of disorder both in the low-temperature ferromagnetic and in the higher temperature antiferromagnetic state. The field dependence of the intensity and position of the magnetic reflections in Co3V2O8 reveals a complex sequence of phase transitions in this Kagome staircase compound. For H parallel to a, a commensurate-incommensurate-commensurate transition is found in a field of 0.072 T in the antiferromagnetic phase at 7.5 K. For H parallel to c at low temperature, an applied field induces an unusual transformation from a ferromagnetic to an antiferromagnetic state at about 1 T accompanied by a sharp increase in magnetization.