Magnetism of rare-earth disilicides

Abstract

Magnetic and electrical properties of polycrystalline RSi2 compounds, where R=La-Yb and Y, have been investigated at temperatures ranging from 1.8 K to room temperature using superconducting quantum-interference device (SQUID) magnetometry, ac susceptibility, resistivity, and magnetoresistance measurements. Our data indicate that while PrSi2, ErSi2, and TmSi2 order ferromagnetically at 11, 2.8, and below 1.8 K, respectively, other RSi2 compounds with R=Nd, Eu, Gd, Tb, Dy, and Ho order antiferromagnetically with TN≤39 K. All compounds show Curie–Weiss behavior in the paramagnetic region and the effective moments are found to be close to the free-ion values, gJ [J(J+1)]1/2. Another interesting feature is the observation of second transitions in the cases of Pr, Nd, Eu, Gd, Tb, and Dy compounds. SmSi2, CeSi2, and YbSi2 do not show any magnetic order down to 1.8 K. In the ordered state, all antiferromagnetic compounds have a T3 dependence of resistivity and show a positive magnetoresistance ranging from a few percent to a field of about 25% of the zero-field resistance, for GdSi2 at 4.2 K and a field of 5.5 T. The ferromagnetic compounds exhibit a T2 dependence of resistivity and a large negative magnetoresistance. These observations are found to be consistent with existing theories.