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 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 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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