Thermal variations of the conduction electron polarization in HoAl2

Abstract

The magnetization density of the ferromagnetic compound HoAl₂ has been investigated by polarized neutron diffraction. At low temperature the bulk magnetization corresponds to 9.3μ_B per formula but the form factor analysis leads to a 4f magnetic moment of 8.6μ_B/Ho. It reveals the existence of a large polarization of the conduction electrons, whose spatial extension is compatible with 5d electrons. We have studied the variations of this polarization when the temperature increases. At 25 K, well below the Curie temperature (32 K), most of the polarization has disappeared. At this temperature the magnetization under the experimental field of 46 kOe has only slightly decreased compared to 4.2 K. It is then clear that the decrease of the 5d polarization cannot be directly related to the variation of the 4f magnetic moment.