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A drift method is described for measuring specific heats in intense magnetic fields at low temperatures. Capacitance thermometry is used, and an automated data-collection system utilizes the imbalance of a transformer-ratio-arm bridge to process the capacitance data. The zero-field specific heat must be known, and measurement of the in situ drift in zero-field calibrates the thermal link. Additional calibration of the link is required if the link’s magnetothermal conductivity effects are significant, and a specific example of a copper-wire link is presented. The method resolves complex structure in the specific heat near a steep λ-type anomaly, as illustrated by measurements on a chromite spinel at 7.5 T. The uncertainty in the method is estimated to be ≂±7%.

Specific heat data are reported for KTa1-x Nb x O3 mixed crystals with x=0.02, 0.03 and 0.09. The absolute value of the Nb concentration was determined by X-ray energy dispersive spectrometry. At the transition temperature T c defined by the peak dielectric constant and the onset of spontaneous birefringence, no anomaly associated with T c is detected in the specific heat. It is suggested that this result provides additional evidence for a diffuse phase transition in quantum ferroelectric KTa1-x Nb x O3. Moreover, for x=0.09, a linear term in the temperature dependence of the specific heat is found below 3 K, in agreement with the general picture of glasslike properties displayed at low temperatures by numerous ferroelectrics.

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