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

摘要

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 he existence of different magnetic moments on two non-equivalent Co(II) ion forming ferromagnetic 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 mu_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.