Magnetic Interaction between Pr³⁺ and Dy³⁺ Spins and Their Spin Transition Induced by Magnetic Field in a Dy₀.₅Pr₀.₅FeO₃ Single Crystal

Rare-earth orthoferrites are receiving ever-increasing attention for their potential applications in magneto-optical switching, multiferroics, and novel physics originating from complicated interactions between magnetic rare-earth and iron ions. In this work, a Dy₀.₅Pr₀.₅FeO₃ single crystal was studied in comparison with DyFeO₃ and PrFeO₃ single crystals to ascertain the effects of interactions between rare-earth spins in Dy₀.₅Pr₀.₅FeO₃ on its magnetic properties. Dy³⁺ and Pr³⁺ spins do not behave as separate entities in Dy₀.₅Pr₀.₅FeO₃. The interaction between them was found to be the strongest below their antiferromagnetic ordering temperature. However, this interaction still persists to substantially higher temperatures. While the ordering temperature of Dy³⁺ spins is field-independent for DyFeO₃, it becomes strongly field-dependent for Dy₀.₅Pr₀.₅FeO₃. External field produces field polarization of nonordered rare-earth spins below ∼25 K for all three systems. High-field-induced spin transition of rare-earth spins was observed for Dy₀.₅Pr₀.₅FeO₃ when a large field H ≥ 3.5 T is oriented along the crystalline a-axis at temperatures below and above the ordering temperature of the rare-earth spins, while the Fe³⁺ spin structure was not affected. This is different from the field-induced spin reorientation of the Dy³⁺ spin structure in DyFeO₃, which occurs only when Dy³⁺ spins are ordered. The complicated behavior of rare earths uncovered in this work further deepens the understanding of such a complex material system.