Double exchange magnets: Spin-dynamics in the paramagnetic phase

TL;DR

This paper investigates the spin dynamics of perovskite manganese oxides in the paramagnetic phase using a Kondo lattice model, revealing ferromagnetic polarons and phase behavior consistent with neutron scattering data.

Contribution

It introduces a finite temperature diagonalization approach to study the electronic structure and spin dynamics in manganites, providing new insights into their paramagnetic phase.

Findings

Dynamic structure factor matches neutron scattering results

Susceptibility exhibits Curie-Weiss behavior

Carriers are ferromagnetic polarons in an antiferromagnetic spin liquid

Abstract

The electronic structure of perovskite manganese oxides is investigated in terms of a Kondo lattice model with ferromagnetic Hund coupling and antiferromagnetic exchange between $t_{2g}$-spins using a finite temperature diagonalization technique. Results for the dynamic structure factor are consistent with recent neutron scattering experiments for the bilayer manganite La$_{1.2}$Sr$_{1.8}$Mn$_2$O$_7$ . The susceptibility shows Curie-Weiss behaviour and is used to derive a phase diagram. In the paramagnetic phase carriers are characterized as ferromagnetic polarons in an antiferromagnetic spin liquid.