Nonuniversal critical behavior in a disorder-destroyed charge-ordering system of Pr0.3Nd0.2Sr0.5MnO3

Abstract

Disorder-induced collapse of the charge-ordered state was found in a half-hole-doped manganite Pr0.3Nd0.2Sr0.5MnO3 by means of studying the magnetic and critical behaviors. Large magnetic frustration originated from the strong competition between ferromagnetic and antiferromagnetic interactions led to the absence of long-range charge ordering. The critical exponents determined for the ferromagnetic-to-paramagnetic phase transition by employing the Kouvel-Fisher method are not consistent with any universality classes, but in between the mean-field and 3D Heisenberg models. It is suggested that the Pr/Nd-site disorder destabilizes the charge-ordered state, and breaks the long-range charge-ordering system into the fragment of antiferromagnetic clusters, which coexist with the ferromagnetic background. Such ionic disorder-induced highly magnetic inhomogeneity is responsible for the nonuniversal critical behavior.