Aa. Mukhin et al., INFLUENCE OF MAGNETIC VACANCIES ON SPIN EXCITATIONS IN THE RARE-EARTHORTHOFERRITES RFE1-XALXO3 (R=GD, HO), Physics letters. A, 198(2), 1995, pp. 158-162
We have observed a strong influence of non-magnetic impurity Al3+ ions
(magnetic vacancies) on spin excitations in GdFe0.9Al0.1O3 and HoFe0.
925Al0.075O3 at frequency nu = 2-33 cm-1. A significant growth of the
frequencies of both AFMR modes nu1 and nu2 at low temperatures was fou
nd in GdFe0.9Al0.1O3 compared to pure GdFeO3. The anomalies observed i
n the behaviour of the AFMR modes for HoFe0.925Al0.075O3 at T(M) = 60
K give evidence of a new first-order spin reorientational phase transi
tion from the GAMMA4(GxFz) phase to the antiferromagnetic phase GAMMA1
(G(y)) induced by the magnetic vacancies.