Magnetic critical behavior of the van der Waals Fe 5 GeTe 2 crystal with near room temperature ferromagnetism

The van der Waals ferromagnet Fe 5 GeTe 2 has a Curie temperature T C of about 270 K, which is tunable through controlling the Fe deficiency content and can even reach above room temperature. To achieve insights into its ferromagnetic exchange that gives the high T C , the critical behavior has been investigated by measuring the magnetization in Fe 5 GeTe 2 crystal around the ferromagnetic ordering temperature. The analysis of the measured magnetization by using various techniques harmonically reached to a set of reliable critical exponents with T C = 273.7 K, β = 0.3457 ± 0.001, γ = 1.40617 ± 0.003, and δ = 5.021 ± 0.001. By comparing these critical exponents with those predicted by various models, it seems that the magnetic properties of Fe 5 GeTe 2 could be interpreted by a three-dimensional magnetic exchange with the exchange distance decaying as J ( r ) ≈ r −4.916 , close to that of a three-dimensional Heisenberg model with long-range magnetic coupling.