Thermal Expansion, Electrical Resistance and the Effect of Hydrostatic Pressure on the Néel Temperature in Fe–Mn Alloys

Abstract

Thermal expansion, temperature change of electrical resistance and its change due to hydrostatic pressure, and magnetic susceptibility were measured with some antiferromagnetic Fe–Mn alloys containing 30 to 40 at% Mn. It was found that an additional magnetic volume expansivity, δV⁄V, due to an antiferromagnetic spin ordering is as large as 10⁻³∼10⁻⁴, and the change of the Néel temperature with pressure, ∂T_N⁄∂P, is about −2.5×10⁻³ deg·Kg⁻¹·cm² in 30 at% Mn alloy. With these values, the volume dependence of the molecular field constant, ∂A⁄∂ω, is estimated to be positive by the molecular field theory with the localized moment model. The results are discussed in comparison with Bethe-Slater’s and Weiss’ theories and with the similar behavior in some ferromagnetic invar-type alloys.