近化学计量比范德华铁磁体Fe₃GeTe₂中的磁各向异性
Magnetic anisotropy in the near-stoichiometric van der Waals ferromagnet Fe$_3$GeTe$_2$
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中文总结 AI 辅助
研究以近化学计量比的Fe₃GeTe₂为对象，通过全面电子自旋共振研究其磁各向异性和自旋动力学。利用频率、温度和磁场依赖的ESR测量，得出磁晶各向异性、磁振子能隙等结果，强调Fe含量对自旋动力学的影响，使其成为探索二维磁体特性的模型材料。
中文摘要 AI 辅助
准二维范德华铁磁体，如Fe₃₋ₓGeTe₂系列，具有较高居里温度和稳健金属性，为研究低维巡游磁性提供理想平台。本文对单晶近化学计量比Fe₃.₀₃±₀.₀₃GeTe₂进行全面电子自旋共振研究。频率依赖的ESR测量确定其为易轴铁磁体；温度依赖的高场ESR揭示高温下逐渐减小的大内部场，且该场在居里温度以上仍存在，证明短程自旋关联。分析自旋波模式得出3K时的强单轴磁晶各向异性和大磁振子能隙。研究强调Fe含量小变化会导致低温磁振子能隙显著变化，表明自旋动力学对化学成分极端敏感。这些结果使Fe₃GeTe₂成为探索金属二维磁体中可调各向异性和磁振子激发的模型范德华铁磁体。
英文摘要
Quasi-two-dimensional (2D) van der Waals (vdW) ferromagnets such as the series Fe$_{3-x}$GeTe$_2$, with a relatively high Curie temperature and robust metallicity, offer an ideal platform for investigating itinerant magnetism in reduced dimensions. Here, we present a comprehensive electron spin resonance (ESR) investigation of single-crystalline almost-stoichiometric Fe$_{3.03 \pm 0.03}$GeTe$_{2}$ across wide ranges of frequencies, temperatures, and magnetic fields to gain quantitative insights into its magnetic anisotropy and spin dynamics. Frequency-dependent ESR measurements establish Fe$_{3}$GeTe$_{2}$ as an easy-axis ferromagnet. Temperature-dependent high-field ESR reveals a large internal field that gradually decreases at higher temperatures. Remarkably, this internal field persists even above $T_\mathrm{C}$, evidencing short-range spin correlations in Fe$_{3}$GeTe$_{2}$. Analysis of spin-wave modes yields a strong uniaxial magnetocrystalline anisotropy $K_{\text{int}} \approx - 5 \times 10^6$ erg cm$^{-3}$ at 3 K and a large magnon gap $Δ(3 \mathrm{K})$ $\approx$ 87.8 $\pm$ 13.7 GHz ($\approx$ 0.363 $\pm$ 0.057 meV). Our study highlights that small variations in Fe content in Fe$_{3}$GeTe$_{2}$ lead to substantial changes in the magnon gap at low temperatures, indicating the extreme sensitivity of spin dynamics to the chemical composition. These results establish Fe$_{3}$GeTe$_{2}$ as a model vdW ferromagnet for exploring tunable anisotropies and magnon excitations in metallic 2D magnets.
