High-Precision Detection of Heat-Capacity Anomaly due to Spin Reorientation in TmFeO3 and HoFeO3

Kazuya SAITO, Akane SATO, Ashis BHATTACHARJEE and Michio SORAI

Anomalies in heat capacity due to spin reorientation transitions have been successfully detected for two orthoferrites by chopped-light ac calorimetry on single-crystals. Onset and completion of the spin reorientation were clearly detected as jumps in heat capacity at 82 and 89 K for TmFeO3 and at 53 and 59 K for HoFeO3. The magnitude of the anomalies is less than 1 % with respect to the total heat capacity at the transition temperatures. The shape of anomalies are compared with available theoretical models.
(Solid State Commun., 120, 129-132 (2001))

Heat Capacity and Magnetic Phase Transitions of Rare-Earth Orthoferrite HoFeO3

Ashis BHATTACHARJEE, Kazuya SAITO and Michio SORAI

Heat capacity of two rare-earth orthoferrite HoFeO3 and LuFeO 3 were measured between 1.8 and 200 K. A distinctly large and two small heat capacity anomalies were detected for HoFeO3 under zero magnetic field around 3.3 K, 53 K and 58 K, respectively. The low-temperature anomaly with a peak at 3.3 K is due to the ordering of Ho3+ ions and the estimated magnetic entropy for this transition was favorably compared with the expected (Rln2). Application of magnetic field significantly affects the positions and the magnitudes of the anomaly at 3.3 K. Energies of low-lying levels of the lowest J-term of Ho3+ ion were roughly estimated through analysis of the Schottky heat capacity.
(J. Phys. Chem. Solids, 63, 569-574 (2002))

Heat-Capacity Anomaly due to Spin Reorientation and Thermodynamic Functions of ErFeO3 and TmFeO3

Kazuya SAITO, Yasuhisa YAMAMURA, Jacek MAYER, Hiroji KOBAYASHI, Yuji MIYAZAKI, Jurgen ENSLING, Philipp GUTLICH, Barbara LESNIEWSKA and Michio SORAI

Heat capacities of orthoferrites, ErFeO3 and TmFeO3 , have been measured below room temperature by adiabatic calorimetry. A broad but definite anomaly due to the spin reorientation phenomenon was successfully detected in the expected temperature range (ca. 90 K). The results are compared with a vast anomaly reported for YbFeO3. The temperature dependence of the electric quadrupole splitting of the Fe nuclear levels was determined by Mossbauer spectroscopy through the spin reorientation. A heat capacity anomaly centered at 3.60 K due to the magnetic ordering of Er3+ ions was clearly detected. Some Schottky anomalies were resolved and energy splittings involved were roughly estimated. Some thermodynamic functions are derived and tabulated.
(J. Mag. Mag. Mat., 225, 381-388 (2001))

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