Effect of rare-earth ions on magnetic properties and spin excitations in manganites

Abstract A qualitative change of a character of Mn ion ordering was observed in RMnO 3 single crystals (R=Sm, Eu, Gd) with decreasing of the R-ion ionic radii (tolerance factor) from Sm to Gd. At low temperatures, a direct magnetic contribution of R ions results in a significant increasing of magnetization in GdMnO 3 and in appearance of a compensation point at 9 K in SmMnO 3 . In the submillimeter transmission spectra we observed magnetic excitations in Sm and Gd subsystems in addition to the antiferromagnetic resonance (AFMR) modes in Mn subsystem.