Determining anisotropy constants from a first-order magnetization process in Tb₂Fe₁₇

The critical parameters of a first-order magnetization process, H_cr and m_cr, are used to determine the anisotropy constants K₁ and K₂ of Tb₂Fe₁₇ in the temperature range between 5 and 300 K. Both anisotropy constants are proportional to the critical field H_cr (times spontaneous magnetization), whereas their ratio is independent of H_cr and depends solely on the dimensionless reduced critical magnetization mcr. The employed method of determining K₁ and K₂ is complementary to the classical Sucksmith–Thompson technique, which is inapplicable in the case of a first-order magnetization process.