Magnetic and structural phase diagram for . Magnetic transition temperatures were obtained from data, while structural data came from refinement of room temperature neutron powder diffraction patterns. Note the abrupt change in on passing from the monoclinic region to the form at .
Neutron diffraction patterns measured with for at (left) and (right), showing that for , the compound remains in the form on cooling and the adopts the form across the temperature range studied. By contrast, the compound changes from a mixture at (consistent with the data in Fig. 3) to primarily at .
ac susceptibility data taken on cooling for measured at using a ac field. The ordering of the and forms at 63(2) and , respectively, shows that both are present. The peak at is due to a minor impurity.
Annealing temperature dependence of the monoclinic fraction present in the sample following cooling to . Data are taken from neutron diffraction (◼, measured at the annealing temperature) and (◻, measured on cooling from the annealing temperature). Inset shows at around the magnetic ordering temperature of the monoclinic phase. On initial cooling (▵), there is a strong signal from the phase, but on reheating from (◻), the signal is essentially gone. Data taken on cooling following annealing at 75 (○) and (◇) show the progressive regrowth of the monoclinic form.
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