Imaging the Magnetic Anisotropy in Ultrathin Fe<sub>4</sub>GeTe<sub>2</sub> with a Nitrogen-Vacancy Magnetometer.
basic_science · Level V
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- Record sourced from PubMed, PMID 38708987.
- Also identified by DOI 10.1021/acs.nanolett.4c00795.
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Abstract
Two-dimensional (2D) Fe<sub><i>n</i></sub>GeTe<sub>2</sub>, with <i>n</i> = 3, 4, and 5, has been realized in experiments, showing strong magnetic anisotropy with enhanced critical temperature (<i>T</i><sub>c</sub>). The understanding of its magnetic anisotropy is crucial for the exploration of more stable 2D magnets and its spintronic applications. Here, we report a quantitative reconstruction of the magnetization magnitude and its direction in ultrathin Fe<sub>4</sub>GeTe<sub>2</sub> using nitrogen vacancy centers. Through imaging stray magnetic fields, we identified the spin-flop transition at approximately 80 K, resulting in a change of the easy axis from the out-of-plane direction to the in-plane direction. Moreover, by analyzing the thermally activated escape behavior of the magnetization near <i>T</i><sub>c</sub> in terms of the Ginzburg-Landau model, we observed the in-plane magnetic anisotropy effect and the formation capability of magnetic domains at ∼0.4 μm<sup>2</sup> μT<sup>-1</sup>. Our findings contribute to the quantitative understanding of the magnetic anisotropy effect in a vast range of 2D van der Waals magnets.