Magnetic Characterization and Low-Temperature Heat Transport Properties of the Orthoferrites RFeO3 ( Rare Earth) Single Crystals

We have studied the magnetic characterization and low-temperature heat transport properties of the orthoferrites RFeO₃ (R = Gd, Dy, Ho, and Y) single crystals. At 40-60 K, the M-T curves with H = 0.1 T (// c) in HoFeO₃ and DyFeO₃ show distinct step-like transitions, which are caused by the spin-reorientation transition of Fe³⁺. The magnetization and specific heat indicate that GdFeO₃ and DyFeO₃ have the antiferromagnetic order of R³⁺ at 2.2 and 4.1 K, respectively, while HoFeO₃ does not exhibit the antiferromagnetic order of R³⁺ at temperatures down to 2 K. Applying the magnetic field along the c-axis, the magnetic structures of R³⁺ or Fe³⁺ can be changed for DyFeO₃ and GdFeO₃. The thermal conductivities (k) of these materials display obvious differences. In particular, the k(T) curve of HoFeO₃ shows a broad concave at 40-140 K, which is caused by the resonant phonon scattering by Ho³⁺. These results point to the clear difference in the interaction between R³⁺ and Fe³⁺ ions among these materials.