Magnetic structure of the GdAl_3 intermetallic compound as seen via M?ssbauer spectroscopy data for ~(119)Sn impurity atoms

摘要

The magnetic hyperfine interaction for ~(119)Sn impurity atoms in GdAl_3 frustrated antiferromagnetic compound has been investigated by Mssbauer 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 Mssbauer spectrum provide an opportunity to propose a plausible model of the spin arrangement in the GdAl_3 lattice. In each GdAl_3 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 GdAl _3 planes. The anomalous temperature behavior of the hyperfine field is characteristic of frustrated systems with competing exchange interactions.