Perturbed-angular-correlation studies in hafnium doped La_0.67Ca_0.33MnO₃

Abstract

¹⁸¹Ta perturbed-angular-correlation (PAC) spectroscopic measurements have been carried out in 0.5 at.% Hf doped La_0.67Ca_0.33MnO₃ samples to understand the electronic and local structural property at the site(s) of substitution of the probe nuclei. Predominantly two fractions are observed which is understood to be due to occupancy of probe atoms at two distinct Mn sites. Based on systematic PAC studies of the sample subjected to vacuum quenching/oxygen annealing treatments it is inferred that these sites are due to the probe atoms occupying Mn⁴⁺ and Mn³⁺ rich sites, bringing out the occurrence of electronically segregated/chemically inhomogeneous phases. These phases are characterized in terms of electric field gradients at Mn sites. quadrupole parameters experienced by the probe atoms occupying Mn³⁺ rich sites are observed to be quite sensitive to vacuum quenching/oxygen annealing treatments. Significantly different quadrupole parameters in the present system as compared to undoped LaMnO₃ is understood mainly based on the difference in the electronic properties of the systems.