Neutron diffraction studies of canted antiferromagnetic ordering in Co II hydroxide terephtalate

The magnetic structure of fully deuterated Co(II) hydroxy terephthalate Co ₂(OD) ₂(tp-d4) (tp-d4=C ₈D ₄O ₄) ( 1) has been determined at various temperatures by neutron powder diffraction analysis. The layered nuclear structure is in agreement with that found from X-ray powder diffraction data and the hydrogen atoms (D) were located in the crystallographic cell. Below the ordering temperature, T_C=48 K, the magnetic diffraction patterns reveal the existence of different magnetic moments on two non-equivalent Co(II) ions forming ferrimagnetic layers. Zero-field cooled experiments show that the long range magnetic order is basically antiferromagnetic along the stacking axis, with possible weak canting within the layers. In field-cooled experiments, strongly canted antiferromagnetism is observed with a net moment of 1.8 μ_B along the b axis. It is shown that this phase is metastable, the weakly canted one being the ground state at very low temperature.