Magnetization Process near the Curie Temperature of a Ferromagnetic Heusler Alloy Co 2 VGa

The field dependence of the magnetization of a ferromagnetic Heusler alloy Co 2 VGa has been measured close to the Curie temperature of 358 K up to an applied field of 50 kOe. Results for samples with different Curie temperatures of 351 K are also reported. The critical exponent δ has been determined to be 4.15 (0.05) for both samples. The value is different from either 5 predicted by the spin fluctuation theory by Takahashi or 3 derived by a conventional molecular field theory. Possible origins for the discrepancy from the theories are discussed.