Continuously Varying Critical Exponents Beyond Weak Universality

N. Khan, P. Sarkar, A. Midya, P. Mandal, P. K. Mohanty

Published 2016-04-26Version 1

We show, from magnetization measurements, that the the critical exponents \beta, \gamma and \delta of the ferromagnetic to paramagnetic transition in [Sm_{1-y}Nd_{y}]_{0.52}[Sr]_{0.48}MnO_3 vary continuously with Nd concentration (y>0.4) and the critical line eventually ends at the Heisenberg universality class in three dimension when y=1. Continuous variation of these three critical exponents violate both universality and weak universality hypothesis. We propose a new scaling ansatz which explains the observed variation of exponents and suggests that the y-dependence of critical exponents does not lead to new universality, rather they are only Heisenberg fixed points with rescaled exponents. The proposed scaling hypothesis includes weak universality as a special case and provides a generic route leading to continuous variation of critical exponents and multicriticality.