Magnetic and Electrical Properties of Dilute Palladium - Palladium-Iron and Palladium-Iron Alloys

Detailed measurements of the field and temperature dependent ac susceptibility of a number of Pd based alloys, fourteen PdNi alloys containing between 2 and 5 at% Ni, seven PdFe alloys containing between 0.35 and 2.4 at% Fe, and five (PdFe)Mn alloys containing between 0.35 and 2.2 at% Fe, are presented. Attempts are made to analyse these data for Curie temperature and critical exponent values. It is shown that for most of the alloys studied, reliable estimates for critical exponents are precluded by the spin -orbit induced anisotropy, though ferromagnetic Curie temperatures T_{c} still can be determined. High-resolution measurements of the ac magnetoresistance in the PdNi, PdFe, and (PdFe)Mn alloys have been carried out at low temperature. These data demonstrate the application of magnetoresistance measurements to investigate the onset of magnetic ordering via the appearance of a spontaneous resistive anisotropy (SRA) in low field, leading to the accurate determination of the critical Ni concentration x_0 in PdNi necessary to establish a ferromagnetic ground state. The first demonstration of a power-law relation between the SRA and the reduced composition near x_0 is presented, and the corresponding critical exponent governing this relationship is estimated experimentally. The effects of hydrogen on a typical sample, 5.0 at% Ni, have also been studied. It is shown that hydrogen has enormous effects on the geometry, susceptibility, and coercive field of the sample.