The role of CDW gap on the magnetic phase transition in CMR materials

Abstract

:We propose a model to study the magnetic phase transition in the Colossal-Magneto-Resistance (CMR) material of general type R 1-x A x MnO 3 (R = La, Sm, Nd; A = Ca, Sr, Ba). The model Hamiltonian consists of a Charge Density Wave (CDW) gap in the e g -band and the strong magnetic field due to the spin ordering in the localized t g core electrons. The Hamiltonian is solved by using Zubarev's Green's function technique to calculate CDW gap (∆) and magnetization (M d ) in t 2g band. Both of them are solved self-consistently. Their combined effect on the temperature dependent magnetization (M c ) due to the e g band electrons is investigated. Both the magnitude and the transition temperature of (M c ) are strongly influenced by both ∆ and M d . Hence the hopping of the band electrons are strongly controlled by these two long range interactions. The results are discussed by varying the model parameters of the manganite system.

Theoretical study of anisotropy in orbital and antiferromagnetic spin orderings in CMR manganites

“…Microscopic model study and phase diagram of multiferroic perovskite manganites (Mochizuki and Furukawa, 2009) shows that the strength of NN and NNN coupling are comparable and the NNN coupling plays a vital role in determining the magnetic properties. Considering only the NN interaction in a DE model in the presence of ferromagnetism (FM) and charge ordering (CO), the studies of magnetisation (Rout et al, 2009a;Panda and Rout, 2009), magnetic susceptibility , velocity of sound (Rout and Panda, 2009), Raman spectra ) and for AFM-CO manganites study of the tunnelling conductance spectra (Panda et al, 2016) successfully explained MI transition and strong electron-phonon interaction in CMR manganites. Further the studies of magnetic susceptibility (Rout et al, 2007), magnetoresistivity (Rout et al, 2009b) for an FM-JT model in the presence of hybridisation interaction between conduction and core electrons and study of resistivity for the same FM-JT model in the presence DE interaction (Rout et al, 2011;Panda et al, 2012) explain the CMR effect below T C .…”

Theoretical study of anisotropy in orbital and antiferromagnetic spin orderings in CMR manganites

“…Microscopic model study and phase diagram of multiferroic perovskite manganites (Mochizuki and Furukawa, 2009) shows that the strength of NN and NNN coupling are comparable and the NNN coupling plays a vital role in determining the magnetic properties. Considering only the NN interaction in a DE model in the presence of ferromagnetism (FM) and charge ordering (CO), the studies of magnetisation (Rout et al, 2009a;Panda and Rout, 2009), magnetic susceptibility , velocity of sound (Rout and Panda, 2009), Raman spectra ) and for AFM-CO manganites study of the tunnelling conductance spectra (Panda et al, 2016) successfully explained MI transition and strong electron-phonon interaction in CMR manganites. Further the studies of magnetic susceptibility (Rout et al, 2007), magnetoresistivity (Rout et al, 2009b) for an FM-JT model in the presence of hybridisation interaction between conduction and core electrons and study of resistivity for the same FM-JT model in the presence DE interaction (Rout et al, 2011;Panda et al, 2012) explain the CMR effect below T C .…”