Electron paramagnetic resonance (EPR) of antiferromagnetic nanoparticles of La 1− xSr xCrO 3 (0.000 ≤ x ≤ 0.020) synthesized by combustion reaction

Abstract

Nanocrystalline particles of La 1− x Sr x CrO 3 (0.000 ≤ x ≤ 0.020) compounds were synthesized in order to investigate the antiferromagnetic (AFM) to paramagnetic (PM) phase transition temperature, g-factor, line width and intensity by electron paramagnetic resonance (EPR). All samples were synthesized by combustion reaction method using strontium nitrate, lanthanum nitrate, chromium nitrate and urea as fuel without subsequent heat treatment. X-ray diffraction patterns of all systems showed broad peaks consistent with orthorhombic structure of LaCrO 3. The absence of extra reflections in the diffraction patterns of as-prepared materials ensures the phase purity. The average crystallite sizes determined from the prominent (1 1 2) peak of the diffraction using Scherrer's equation was independent of the addition of Sr 2+ ions; being ca. 31–29 nm for x = 0.000 and 0.020, respectively. The EPR line width and intensity were found to be dependent on Sr 2+ addition and temperature. However, the AFM–PM transition temperature was found to be independent of strontium concentration, being ca. 296 K. In the PM phase, g-factor was nearly temperature independent with increasing of x. The EPR results indicated that the addition of Sr 2+ ions may induce creation of Cr 3+–Cr 4+ clusters.