Anisotropic phonon conduction and lattice distortions in CMR-type bilayer manganite (La$_{1-z}$Pr$_{z}$)$_{1.2}$Sr$_{1.8}$Mn$_{2}$O$_{7}$ (z=0,0.2,0.4 and 0.6) single crystals

TL;DR

This study investigates how Pr-substitution affects anisotropic thermal conductivity and lattice distortions in bilayer manganite single crystals, revealing a giant magnetothermal effect linked to orbital state occupation and lattice relaxation models.

Contribution

It provides a systematic analysis of thermal conductivity variations with Pr content and magnetic field, highlighting anisotropic effects and the role of lattice distortions in these materials.

Findings

Pr-substitution alters thermal conductivity anisotropically.

Giant magnetothermal effect correlates with magnetization.

Lattice distortions are explained by local relaxation models.

Abstract

We have undertaken a systematic study of thermal conductivity as a function of temperature and magnetic field of single crystals of the compound (La$_{1-z}$Pr$_{z}$)$_{1.2}$Sr$_{1.8}$Mn$_{2}$O$_{7}$ for $z$(Pr) =0.2,0.4. and 0.6. The lattice distortion due to Pr-substitution and anisotropic thermal conductivity in bilayer manganites are discussed on the basis of different relaxation models of local lattice distortions in metal and insulating states proposed by Maderda et al. The giant magnetothermal effect is scaled as a function of magnetization and discussed on the basis of a systematic variation of the occupation of the $e_g$-electron orbital states due to Pr-substitution.