Hyperfine interactions in intermetallic rare earth-gallium compounds studied by 111 Cd PAC

Abstract

Magnetic and electric hyperfine interaction of the nuclear probe 111In/111Cd in intermetallic compounds of the rare earth-gallium system have been investigated by perturbed angular correlation (PAC) spectroscopy. The PAC measurements, supported by X-ray diffraction, provide evidence for a marked phase preference of 111In for hexagonal RGa2 over orthorhombic RGa and of RGa3 with the L12 structure over RGa2. In the case of SmGa2, the magnetic hyperfine field Bhf, the electric quadrupole interaction and the angle β between Bhf and the symmetry axis of the electric field gradient have been determined as a function of temperature. The angle β = 0 is consistent with the results of previous magnetization studies. Up to T ≤ 17 K the magnetic hyperfine field has a constant value of Bhf = 3.0(2) T. The rapid decrease at higher T gives the impression of a first-order transition with an order temperature of TN = 19.5 K. In the RKKY model of indirect 4f interaction the ratio TC/Bhf(0) is a measure of the coupling constant. For 111Cd:SmGa2 (TC/Bhf(0)~6.5 K/T) this ratio is significantly smaller than for the same probe in other R intermetallics (SmAl2 ~9.5 K/T, Sm2In ~13.5 K/T).