Magnetic hyperfine field in antiferromagnetic RGa_2 (R = Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er) studied by perturbed angular correlation spectroscopy using ~(111)Cd

摘要

The magnetic and electric hyperfine interactions of the nuclear probe ~(111)Cd in the hexagonal antiferromagnetic rare earth-gallium RGa_2 (R = Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, and Er) intermetallic compounds have been investigated by perturbed angular correlation (PAC) spectroscopy as a function of temperature. With the exception of R = Nd and Ho, the magnetic hyperfine field B_(hf) is roughly proportional to the spin projection (g - 1)J of the R constituent. However, in the group of the light rare earths, the variation of B_(hf) with (g - 1)J is much weaker than that for the heavy R constituents, in contrast to the trend reported for all rare earth intermetallics investigated up to now as well as to the trend of the magnetic ordering temperatures of RGa_2. The orientation of the 4f spins relative to the c axis of RGa_2 deduced from the angle between B_(hf) and the symmetry axis of the electric field gradient was found to be temperature independent and in agreement with the results of previous magnetization measurements. Except for SmGa_2 where the hyperfine field shows an abrupt decrease near T_N, the temperature dependence of B_(hf)(T) is consistent with second order phase transitions. The magnetic ordering temperatures deduced from B_(hf)(T) agree with magnetization and neutron diffraction results.