Resistivity and magnetoresistance properties of R2NiSi3 (R = Gd, Dy, Ho, Er, Tm) compounds

The resistivity and magnetoresistance behaviour of the hexagonal intermetallic compounds R2NiSi3 (R = Gd, Dy, Ho, Er, and Tm) are reported here. All the studied polycrystalline compounds exhibit metallic behaviour along with additional magnetic anomalies at low temperatures. A well-defined resistivity minima is observed in Gd2NiSi3 and Dy2Ni0.87Si2.95 at a temperature much higher than their respective magnetic transition temperatures. The anomaly has been ascribed to the charge carrier localization caused by magnetic precursor effect. Magnetic field induced crossover from positive to negative magnetoresistance (MR) behaviour associated with antiferromagnetic ground state is evidenced for Gd2NiSi3 and Er2NiSi3 in the low temperature region. Although Tm2Ni0.93Si2.93 does not exhibit any long range magnetic order down to 2 K, a sudden drop in resistivity behaviour is observed below 10 K. Presence of short range magnetic correlation observed in a wide temperature range, much beyond their respective magnetic ordering temperatures, has been argued to be responsible for achieving finite negative MR for all the compounds. A subtle resemblance between the observed transport anomalies and the magnetic properties of these systems have been discussed.