Effect of the magnetic field on the ferroelectric transition of KD2PO4 measured by a high resolution and super-sensitive differential scanning calorimeter

The magnetic effect on the ferroelectric transition of single crystalline KD2PO4 (DKDP) was measured by using a high resolution and super-sensitive differential scanning calorimeter (DSC) working in a magnetic bore. The transition temperature of KD2PO4 with the magnetic field of 5 T along a-axis and along c-axis was 5.6 ± 0.8 and 2.8 ± 0.9 mK, respectively, higher than that without the magnetic field. The calculated temperature shifts of the transition due to the magnetic field along a-axis and along c-axis using the magneto-Clapeyron equation and the data of magnetic susceptibility were negative values, being contradictory to the experimental results. These results demand to consider another contribution in magnetic susceptibility. The high frequency term of magnetic susceptibility due to molecular motions was considered to play an important role in order to explain the positive experimental values.