Critical behavior of the van der Waals ferromagnet Fe4.8GeTe2

The van der Waals ferromagnet Fe5-xGeTe2 has drawn significant interest due to its approximately room-temperature Curie temperature (T-C) of 270 to 310 K, which can be regulated through iron deficiency. To comprehend the tunable T-C associated with the ferromagnetic exchange mechanism, we systematically investigate the critical phenomenon of Fe5-xGeTe2 (Fe4.8GeTe2) crystals around T-C. Employing diverse analytical methods for magnetization study, we derived reliable critical exponent values: T-C = 285 K, beta = 0.364(2), gamma = 1.293(1), and delta = 4.62(1). Through a comparative analysis of these critical exponents, the magnetic behavior of Fe4.8GeTe2 is expounded as a three-dimensional (3D) magnetic exchange mechanism, with exchange distance decay modeled as J(r) approximate to r(-4.85), closely resembling long-range magnetic coupling in the 3D Heisenberg mode.