Magnetic and thermodynamic properties of RMnO₃ (R = Pr, Nd)

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The ground state properties of the pure perovskite compounds PrMnO₃ and NdMnO₃ were investigated by magnetization, magnetic AC susceptibility and specific heat measurements. A strongly anisotropic behavior has been detected for temperatures below the antiferromagnetic phase transition Tₙ 100K. The susceptibility and the weak spontaneous ferromagnetic moment appear to be different in both compounds due to different anisotropic rare earth contributions. The specific heat shows strong Schottky type contributions at low temperatures, which for NdMnO₃ strongly depend on the magnetic field. A spin reorientation phase transition (spin-flop type) induced by a magnetic field along b axis was observed in NdMnO₃ at H 110kOe and T=5K. All results can consistently be explained by anisotropic contributions of the rare earth ions: In PrMnO₃ the electronic ground state is determined by a low lying quasidoublet split by the crystal field 19 K. In NdMnO₃ the Kramers doublet is split by an exchange Nd-Mn field (20K).