High-Field Dependence of the Magnetization in Fe-Al Alloys

An increase in magnetization with an increase of the magnetic field well above technical saturation were measured at 4.2 K for single crystals of Fe-Al alloys in the directions of easy magnetization in the fields up to 55 kOe which is produced by a superconducting magnet, using an integrating digital voltmeter. From the slope of the linear part of the magnetization curves in the high fields, the magnitudes of the high-field susceptibility were estimated to be 4.4, 5.0, 4.8, 6.1, 7.2, 53, 83 and 88×10 -4 emu/mole for 17.3, 20.1, 23.0, 24.9, 25.0, 27.1, 27.7 and 28.1 at.% Al-Fe, respectively. The observed behavior of the composition dependence of the high-field susceptibility can be interpreted on the basis of either the Pauli paramagnetism of 3d electrons, or a coexistence of ferromagnetic Fe 3 Al phase and antiferromagnetic FeAl phase.