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稀土正铁氧体(RFeO3,R为稀土原子)包含Fe3+和R3+两套磁性离子亚晶格，存在Fe3+-Fe3+、Fe3+-R3+、R3+-R3+三种相互作用，它们是稀土正铁氧体丰富磁性的来源。本文利用时域太赫兹磁光谱，在1.6至300 K的温度范围内，在不同磁场下，测量a-cut DyFeO3单晶样品的吸收光谱，并分析光谱中铁磁(FM）和反铁磁共振（AFMR）吸收峰的温度和磁场依赖特性。在零磁场变温实验中，我们发现随温度降低在Morin温度(
~50 K)出现的温度诱导的自旋重取向(Γ4 ®Γ1)，以及在4 K温度以下存在一个由于电磁振子导致的宽带吸收。在Morin温度以上，我们在恒定温度(70 K、77 K、90 K和100 K)下测量了样品在0至7 T磁场范围的吸收光谱。实验结果表明，随着磁场的增加，存在一个新的磁相变过程(Γ4→Γ24→Γ2→Γ24→Γ2)，相变的临界磁场随温度而变化。这一相变过程是由于外磁场和Fe3+-Dy3+的各向异性交换相互作用导致的内部有效场的相互竞争和对磁矩的协同作用。本项研究为深入理解稀土铁氧化物的丰富相变和磁电耦合特性，以及开发相关的自旋电子学器件提供参考。 Rare-earth orthoferrites (RFeO3) have garnered significant attention due to their intricate magnetic interactions and potential applications in ultrafast spintronic devices. Among them, DyFeO3 exhibits rich magnetic phase transitions driven by the interplay of Fe³⁺ and Dy³⁺ sublattices. While previous studies focused on temperature-induced spin reorientation near the Morin temperature (TM∼50 K), the magnetic phase behavior under external fields above TM remains less explored. This work aims to systematically investigate the temperature- and magnetic-field-dependent magneto-dynamic properties of a-cut DyFeO3 single crystals, with an emphasis on identifying novel phase transitions and elucidating the underlying mechanisms involving Fe³⁺-Dy³⁺ anisotropic exchange interactions. High-quality a-cut DyFeO3 single crystals were grown using the optical floating zone method and characterized via XRD and Laue diffraction. Time-domain terahertz spectroscopy (THz-TDS) coupled with a superconducting magnet (0-7 T, 1.6-300 K) was employed to probe the ferromagnetic resonance (FM)and antiferromagnetic resonance (AFMR) modes. By analyzing the frequency trends in the spectra, we infer the response of internal magnetic moments to external stimuli. In the zero magnetic field experiment, we find that the temperature induced spin reorientation ( Γ 4→ Γ 1) occurs at Morin temperature(~50 K) with decreasing temperature. A broadband electromagnetic absorption (0.45-0.9 THz) emerged below 4 K, attributed to electromagnons activated by broken inversion symmetry in the Dy³⁺ antiferromagnetic state. Above the Morin temperature, we measured the absorption spectra of the sample at constant temperatures (70 K, 77 K, 90 K, and 100 K) in the 0 to 7 T magnetic field range. The experimental results show that with the increase of magnetic field, there exists a new magnetic phase transition ( Γ4→Γ24→Γ2→Γ24→Γ2 ), and the critical magnetic field of the phase transition changes with temperature. The phase transitions arise from the competition between external magnetic fields and internal effective fields generated by anisotropic Fe³⁺-Dy³⁺ exchange. These findings advance the understanding of magnetoelectric effects in RFeO3 systems and provide a roadmap for designing spin-based devices leveraging field-tunable phase transitions.-
Keywords:
- rare-earth orthoferrite /
- terahertz /
- magnetic resonance /
- magnetic phase transition
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