Calorimetric and neutron diffraction studies of the commensurate - incommensurate spin-density-wave phase transition of Cr+0.3 at.% Ru alloy

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Abstract
Calorimetric and time-of-flight neutron diffraction experiments are used to establish thermodynamic and structural features of a Cr+0.3 at.% Ru alloy crystal as it undergoes a commensurate-to-incommensurate spin-density-wave (CDSW - ICDSW) phase transition. Both methods confirm the first-order character of the transition. The calorimetric measurements made at the CSDW - ICSDW transition, using a differential scanning microcalorimeter, show that the latent heat and entropy changes at the transition are small: the transition is only weakly first order. The difference between the specific heat of the incommensurate phase and that, , of the commensurate phase is determined as . In the neutron diffraction experiments the thermal evolution of the intensities and positions of the commensurate and the incommensurate peaks have been monitored in the region of the transition. There is a temperature range of approximately 28 K in which the commensurate and the incommensurate peaks coexist. This coexistence of the two phases is consistent with a broad anomaly observed in the specific heat.