Nonlocal quartic interactions and universality classes in perovskite manganites.
A modified Ginzburg-Landau model with a screened nonlocal interaction in the quartic term is treated via Wilson's renormalization-group scheme at one-loop order to explore the critical behavior of the paramagnetic-to-ferromagnetic phase transition in perovskite manganites. We find the Fisher exponent η to be O(ε) and the correlation exponent to be ν=1/2+O(ε) through epsilon expansion in the parameter ε=d(c)-d, where d is the space dimension, d(c)=4+2σ is the upper critical dimension, and σ is a parameter coming from the nonlocal interaction in the model Hamiltonian. The ensuing critical exponents in three dimensions for different values of σ compare well with various existing experimental estimates for perovskite manganites with various doping levels. This suggests that the nonlocal model Hamiltonian contains a wide variety of such universality classes.
Department of Physics, Indian Institute of Technology Guwahati, Guwahati 781 039, India.
Rohit
R
Singh
Department of Physics, Handique Girls' College, Guwahati 781 001, India.
Kishore
K
Dutta
Department of Physics, Indian Institute of Technology Guwahati, Guwahati 781 039, India.
Malay K
MK
Nandy