The interplay between double exchange, super-exchange, and Lifshitz localization in doped manganites

Abstract

Considering the disorder caused in manganites by the substitution of Mn by Fe or Ga, we accomplish a systematic study of doped manganites begun in previous papers. To this end, a disordered model is formulated and solved using the Variational Mean Field technique. The subtle interplay between double exchange, super-exchange, and disorder causes similar effects on the dependence of T_C on the percentage of Mn substitution in the cases considered. Yet, in La${}_{2/3}$Ca${}_{1/3}$Mn${}_{1-y}$Ga${}_y$O${}_3$ our results suggest a quantum critical point (QCP) for $y\approx 0.1-0.2$, associated to the localization of the electronic states of the conduction band. In the case of La${}_x$Ca${}_x$Mn${}_{1-y}$Fe${}_y$O${}_3$ (with $x=1/3,3/8$) no such QCP is expected.

6 pages + 3 postscript figures. Largely extended discussion

References in corpus (5)

• Colossal Effects in Transition Metal Oxides Caused by Intrinsic Inhomogeneities
• Metamagnetic Quantum Criticality
• Disorder induced cross-over effects at quantum critical points
• Monte Carlo determination of the phase diagram of the double-exchange model
• Quantum phase transitions of correlated electrons in two dimensions

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• Nucleation, instability, and discontinuous phase transitions in monoaxial helimagnets with oblique fields
• Effect of oxygen isotope substitution and crystal micro-structure on magnetic ordering and phase separation in {$(\mathrm{L}{\mathrm{a}}_{1-\mathrm{y}}\mathrm{P}{\mathrm{r}}_{\mathrm{y}}{)}_{0.7}\mathrm{C}{\mathrm{a}}_{0.3}\mathrm{Mn}{\mathrm{O}}_3$}
• Study of the One- and Two-Band Models for Colossal Magnetoresistive Manganites Using the Truncated Polynomial Expansion Method
• Evidence for strong effect of quenched correlated disorder on phase separation and magnetism in (La_{1-y}Pr_{y})_{0.7}Ca_{0.3}MnO_3
• Effect of Mn substitution by Ga on the optical properties of a metallic manganite
• Phase diagram of the (bosonic) Double-Exchange Model
• Ferromagnetic to spin glass cross over in (La,Tb)_{2/3}Ca_{1/3}MnO_{3}
• Dynamical generation of a gauge symmetry in the Double-Exchange model
• Spin excitations in systems with hopping electron transport and strong position disorder in a large magnetic field
• Substitutional disorder and charge localization in manganites