Magnetoresistance (MR) measurements on the antiferromagnetically ordered polycrystalline $R_2{\mathrm{Ni}}_3{\mathrm{Si}}_5$ ($R=\mathrm{P}\mathrm{r},\mathrm{D}\mathrm{y},\mathrm{H}\mathrm{o}$; $T_N=8.5\mathrm{} \mathrm{K}, 9.5 \mathrm{K}, 6.0 \mathrm{K}$, respectively) materials are reported here. Field dependence of MR, measured both below and above their respective ordering temperatures and up to a field of 45 kOe, is found to be anomalous. In all the three cases, in the magnetically ordered state, MR is not monotonic but exhibits a maximum and a minimum. A considerable contribution to MR, with nearly linear field dependence and persisting even above the magnetic ordering temperature, is observed, which is unusual. Temperature dependence of MR (in a constant high field) above the magnetic ordering temperature, measured up to 100 K, exhibits a pronounced hump. The behavior of magnetoresistance at low temperatures is interpreted in terms of metamagnetism along with a short range ferromagnetic interaction.

• Received 16 February 1996

DOI:https://doi.org/10.1103/PhysRevB.54.6069