Electrical properties of exchange-enhanced systems: Fe in (Pd95Rh5)

The electrical resistivity of the giant moment system Pd₉₅Rh₅ containing between 0.8 and 1.85 at % Fe has been measured from 1.4 to 300 K. The incremental resistivity in alloys containing more than 1.25 at % Fe is found to exhibit aT ² limiting low-temperature form; however for the 0.8 and 1.1 at % Fe alloys such aT ² form is not clearly discernible, with (T) exhibiting a temperature dependence intermediate betweenT ² andT ^3/2. The former result is predicted from conduction electron-magnon scattering for which wave vector conservation holds, from which it is inferred that the criterion for wave vector conservation in this type of alloy isnot determined by mean free path effects. Estimates of the acoustic spin-wave stiffnessD are derived from the measuredT ² coefficients. These resistivity data also enable estimates of the exchange coupling parameterJ _s-local to be made. The magnetic ordering temperatureT _c is considerably less discernible than in single-component hosts but approximate values have been derived for the various alloys, from which estimates of the exchange coupling parameterJ _d-local have been made. In the disordered phase the measured incremental resistivity is found to contain a term which decreases approximately linearly with increasing temperature, at a rate of –(1.1±0.45)10^–3 µ cm/K at % Fe. Using existing pressure data on both Pd- and PdRh-based alloys, it is shown that both the sign and magnitude of this term can be accounted for in terms of the volume dependence of the potential and exchange terms, in conjunction with a large coefficient of thermal expansion.This work has been supported in part by the Defence Research Board under Grant No. 9510-100.