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 ¹¹¹In→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 T _C 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 T _C for each compound. However, in the measurements with ¹¹¹Cd at In sites, the mhf values become zero at temperatures which are smaller than T _C . The difference between the temperatures at which mhf is zero for ¹⁴⁰Ce and ¹¹¹Cd probes correlates with T _C . For each compound this difference decreases with T _C . 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.