Hall Effect Studies in Fe₆₅(Ni_1−xMn_x)₃₅ Alloys

Abstract

The temperature dependence of the Hall effect has been measured in the Invar type f.c.c. Fe₆₅(Ni_1−xMn_x)₃₅ alloys. The experimental results can be fairly well represented by the equation, R_o^*=R_o+R_e·4π(∂M⁄∂H). The behavior of the apparent Hall coefficient R_o^* is closely connected with the magnetic properties of the alloys. Especially in the antiferromagnetic concentration region; 1) for x=0.4 and 0.5, the coefficient R_o^* has a maximum at the Néel temperature, which may be associated with the maximum of the magnetic susceptibility χ, 2) for x=0.8 and 1.0, there is no maximum at the Néel temperature in R_o^* and χ either, but R_o^* shows a monotonic increase with decreasing temperature below the Néel temperature, which seems to correspond to the formation of an energy gap in momentum space due to antiferromagnetic ordering, as in the case of Cr. The positive sign of the presumed ordinary Hall coefficient suggests that the 3d-holes greatly contribute to the conduction.