Electron paramagnetic resonance studies on manganite Pr_(0.)5Sr_(0.5)Mn_(1-x)Ga_XO_3 (x = 0 and 0.05)

摘要

In this paper, we present the investigations of electron paramagnetic resonance on perovskite manganite Pr_(0.5)Sr_(0.5)Mno_3 and Ga-doped Pr_(0.5)Sr_(0.5)Mn_(0.95)Ga_(0.05)O_3. The temperature dependent paramagnetic resonance spectra parameters (effective g-factor, peak-to-peak linewidth ΔHpp and double integrated intensities) have been used to study the paramagnetic spin correlations and spin dynamics. The gradual increase of effective g-factor is attributed to the presence of orbital ordering above T_C. The model fittings of temperature dependent double integrated intensities reveal Arrhenius law is appropriate for describing Pr_(0.5)Sr_(0.5)Mn_(0.95)Ga_(0.05)O_3 instead of Pr_(0.5)Sr_(0.5)MnO_3 system. As for Pr_(0.5)Sr_(0.5)MnO_3, the broadening of linewidth with the temperature increase origins from the contribution of small polaron hopping in the PM regime. However, as for Pr_(0.5)Sr_(0.5)Mn_(0.95)Ga_(0.05)O_3, the broadening of EPR linewidth can be understood with the spin-lattice relaxation mechanism.