Magnetic and Transport Properties of the Kondo Lattice Model with Ferromagnetic Exchange Coupling

TL;DR

This paper investigates the magnetic and transport properties of a Kondo lattice model with ferromagnetic exchange coupling, revealing ferromagnetic instabilities and giant magnetoresistance consistent with experimental data on manganites.

Contribution

It introduces a classical spin limit approach to the Kondo lattice model, providing insights into ferromagnetic behavior and magnetoresistance in manganite materials.

Findings

Ferromagnetic instabilities occur at lower temperatures in hole-doped systems.

Giant magnetoresistance matches experimental observations in (La,Sr)MnO$_3$.

Model accurately reproduces key magnetic and transport phenomena.

Abstract

The Kondo lattice model with Hund's ferromagnetic spin coupling is investigated as a microscopic model of the perovskite-type $3d$ manganese oxide (R,A)MnO$_3$ where $R$ and $A$ are rare earth element and alkaline earth element, respectively. We take the classical spin limit $S=\infty$ for the simplicity of the calculation, since the quantum exchange process seems to be irrelevant in the high temperature paramagnetic phase. Magnetic and transport properties of the system are calculated. In the hole doped systems, ferromagnetic instabilities are observed as the temperature is lowered. The giant magnetoresistance of this model is in excellent agreement with the experimental data of (La,Sr)MnO$_3$.