Magnetic Resonance Investigations of h-YbMnO3

Resumo

Polycrystalline samples of ytterbium manganites have been synthesized with deficiency of Yb³⁺ ions. The X-ray analysis showed that the structure of the sample is hexagonal (h-YbMnO₃) with the space group P6₃cm. The analysis of the X-ray diffraction peak intensities allowed to find the occupancy of Yb³⁺ and Mn³⁺ positions which are about 89 and 100 %, respectively. The electron spin resonance (ESR) measurements were performed using X (9.4 GHz), Q (34.2 GHz) and W (94.1 GHz) bands. The ESR spectrum displays the broad exchange-narrowed Mn³⁺ resonance line and an additional signal, which is attributed to the ferromagnetically correlated clusters, formed by mixed-valence manganese ions near vacant Yb³⁺ positions, confirmed by the observation of the hysteresis loop in the magnetization of h-YbMnO₃.