EMR Study of La_0.887Na_0.113Mn_0.984O₃ and La_0.94Mn_0.98O₃ Single Crystals

The method of Electron Magnetic Resonance (EMR) is fruitfully used during last years for the investigation of the colossal magnetoresistive manganites. Very recent results regarding EMR studies of crushed and bulk single-crystalline La0.887Na0.113Mn0.984O3 and La0.94Mn0.98O3 samples are presented. The main features observed for the resonant spectra of all the samples that are noted: a) gradual change of the broad asymmetric FMR line to narrow EPR line with temperature; b) coexistence of FMR and EPR signals within certain temperature intervals; c) ferromagnetic antiresonance and low field microwave absorption signals; d) minimum of the linewidth in the vicinity of 1.1 T-c and its linear broadening above this temperature; e) double integrated intensity of the signal obeys Arrhenius low above 1.1 T-c; f) specific effect of the non-resonant surface microwave absorption. The results obtained on crushed and bulk crystalline samples are compared. Unusual features observed were related to the presence of intrinsic magnetic inhomogeneities in all of the manganites under consideration. The disputable problems on this field are considered.