Phase competition in the double-exchange model on the frustrated pyrochlore lattice

TL;DR

This paper investigates how geometrical frustration influences phase competition between ferromagnetic and antiferromagnetic states in the double-exchange model on pyrochlore lattices, revealing a transition to a cooperative paramagnetic metal with incoherent transport.

Contribution

It introduces a theoretical analysis of phase competition in a frustrated double-exchange model, highlighting a continuous transition to a paramagnetic metallic state under frustration.

Findings

Ferromagnetic metal becomes unstable with increasing super-exchange.

Transition to a cooperative paramagnetic metal with incoherent transport.

Large residual entropy suggested at low temperatures.

Abstract

Competition between the ferromagnetic double-exchange interaction and the super-exchange antiferromagnetic interaction is theoretically studied in the presence of geometrical frustration. As increasing the super-exchange interaction, the ferromagnetic metal becomes unstable, and is taken over by a cooperative paramagnetic metal, in sharp contrast with a discontinuous transition to the antiferromagnetic insulator in the absence of frustration. In the critical region, the system exhibits a peculiar temperature-independent behavior with highly incoherent transport, suggesting a large residual entropy at low temperatures. We discuss the relevance of the results to the pressure-induced behaviors in Mo pyrochlore oxides [S. Iguchi et al., Phys. Rev. Lett. 102, 136407 (2009)].