Magnetic phase diagram of the Kondo lattice model with quantum localized spins

TL;DR

This study maps the magnetic phase diagram of the ferromagnetic Kondo lattice model across different dimensions and spin magnitudes, revealing minimal influence of quantum spin effects except at S=1/2, supporting classical spin approximations in manganites.

Contribution

It provides a comprehensive analysis of the phase boundaries in the Kondo lattice model for various spin quantum numbers and dimensions, highlighting the special case of S=1/2.

Findings

No significant influence of spin quantum number on phase boundaries except at S=1/2.

Instability of ferromagnetic phase at S=1/2 due to spin disorder.

Supports classical treatment of S=3/2 spins in manganites.

Abstract

The magnetic phase diagram of the ferromagnetic Kondo lattice model is determined at T=0 in 1D, 2D, and 3D for various magnitudes of the quantum mechanical localized spins ranging from S=1/2 to classical spins. We consider the ferromagnetic phase, the paramagnetic phase, and the ferromagnetic/antiferromagnetic phase separated regime. There is no significant influence of the spin quantum number on the phase boundaries except for the case S=1/2, where the model exhibits an instability of the ferromagnetic phase with respect to spin disorder. Our results give support, at least as far as the low temperature magnetic properties are concerned, to the classical treatment of the S=3/2-spins in the intensively investigated manganites, for which the ferromagnetic Kondo-lattice model is generally employed to account for magnetism.