RESISTIVITY, MAGNETORESISTANCE AND FIELD-DEPENDENT AC SUSCEPTIBILITY OF ERNIBC

Measurements are reported on the temperature and field dependence of t he resistivity of ErNiBC between 1.5 and 15 K in fields up to 7 T. The zero-field resistivity displays an abrupt fall below 4.1 K and an ove rall character consistent with ferromagnetic ordering, as inferred fro m recent neutron scattering measurements; the data below 2 K can be re produced by a model describing conduction-electron scattering by spin waves following a gapped dispersion relation: E(q) = Delta + Dq(2), wi th the gap parameter Delta = 2 +/- 0.5 K. Data acquired in various fix ed fields can be adequately reproduced by adding a conventional Zeeman term to Delta. The field-dependent AC susceptibility does not display features normally associated with critical fluctuations at a ferromag netic transition, although here the latter might be obscured by a subs tantial regular contribution, the presence of which could signify cons iderable magnetic anisotropy most likely to be associated with single ion spin-orbit coupling at Er sites.