Proton Resonance Study of the Antiferromagnetic State of Two-Dimensional Cu(HCOO)₂·4D₂O

抄録

Proton resonance experiments up to 60 MHz(14 k0e) were made at 4.2 K. The observed strong field-dependence of nmr spectra is attributed to a field-induced structure change from a 4-sublattice state to a 2-sublattice state. The origin of the transition is ascribed to the two-dimensional character of the interaction path. Rotation of the antiferromagnetic axis was observed in the 2-sublattice state by changing the field direction. The origin of this movement is attributed to the weak ferromagnetism mostly arising from the inequivalence of g-tensors of two copper ions in the unit cell. The large spin-reduction reported by Dupas and Renard was not found in the high field state.