Hyperfine interactions at R and In sites in RNiIn (R = Gd, Tb, Dy, Ho) compounds measured by perturbed angular correlation spectroscopy

Abstract

Perturbed gamma-gamma angular correlation (PAC) technique was used to measure the magnetic hyperfine field (mhf) in RNiIn (R=Gd, Dy, Tb, Ho) intermetallic compounds using the 111 In → 111Cd and 140La → 140Ce probe nuclei. The PAC spectra for 111Cd measured above magnetic transition temperature show a major fraction with a well defined quadrupole interaction for all compounds except GdNiIn where a single frequency was observed. PAC measurements below Te showed a combined electric quadrupole plus magnetic dipole interaction for 111Cd probe at In sites, and a pure magnetic interaction for 140Ce at R sites. The temperature dependence of mhf measured with 140Ce at R sites shows that the values of fields drop to zero at temperatures around the expected Te for each compound. However, in the measurements with 111Cd at In sites, the mhf values become zero at temperatures which are smaller than TC. The difference between the temperatures at which mhf is zero for 140Ce and 111Cd probes correlates with TC. For each compound this difference decreases with TC. The results are discussed in terms of the RKKY model for magnetic interactions and the existence of two magnetic systems, with distinct exchange interaction energies due to different types of atomic layers in these compounds.