AbstractThe van der Waals ferromagnet Fe₅GeTe₂ 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 Fe₅GeTe₂ 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 Fe₅GeTe₂ 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.