Magnetic structure of the intermetallic compound as seen via Mِssbauer spectroscopy data for impurity atoms

The magnetic hyperfine interaction for 119Sn impurity atoms in GdAl3 frustrated antiferromagnetic compound has been investigated by Mِssbauer spectroscopy technique. Two magnetic subspectra with the ratio of the intensities 2:1 were observed. At 4.5 K, the values of the magnetic hyperfine field are 4.00(2) and 1.35(2) T. The peculiarities of the Mِssbauer spectrum provide an opportunity to propose a plausible model of the spin arrangement in the GdAl3 lattice. In each GdAl3 basal layer, the magnetic moments of the Gd atoms form three-sublattice 120° spin structure that is peculiar to magnetically frustrated compounds. The appearance of two magnetically nonequivalent Sn sites is a result of vector summation of the transferred polarizations from Gd moments located in two adjacent GdAl3 planes. The anomalous temperature behavior of the hyperfine field is characteristic of frustrated systems with competing exchange interactions.