Figure 29.

(a) Magnetic susceptibility χ as a function of the temperature T for a Fe₃GeTe₂ single-crystal measured under zero field-cooled (black markers) and field cooled (red markers) conditions. Open markers correspond to the inverse of χ where the blue line is a linear fit. The Curie temperature exceeds 200 K. Adapted with permission from ref (327). Copyright 2017 American Physical Society. (b) χ as a function of T for a Fe₄GeTe₂ single-crystal and for fields along the c-axis (solid green makers) and the ab-plane (open green markers). Solid black markers depict both the resistivity and its derivative indicating a T_c of ∼270 K with another spin-reorientation transition above 100 K. Adapted with permission under a Creative Commons CC BY-NC 4.0 license from ref (88). Copyright 2020 AAAS. (c) Magnetization as a function of the temperature for Fe₅GeTe₂ for fields along the c-axis (open markers) and the ab-plane (solid markers) and also polycrystalline material (gray line). It displays a T_c in excess of 280 K. Adapted with permission from ref (87). Copyright 2019 American Chemical Society.