Effects of selective dilution on the magnetic properties of La_{0.7}Sr_{0.3}Mn_{1-x}M'_xO_3 (M' = Al, Ti)

TL;DR

This study investigates how selective dilution of Mn ions with Al or Ti affects the magnetic transition temperature and magnetization in La_{0.7}Sr_{0.3}MnO_3, revealing a linear relation and scaling behavior explained by molecular-field theory.

Contribution

It introduces a systematic analysis of selective dilution effects on magnetic properties, demonstrating the validity of molecular-field theory for different substituents in La_{0.7}Sr_{0.3}MnO_3.

Findings

$T_c$ decreases linearly with dilution concentration.

Scaling behavior of $T_c$ fits molecular-field theory.

Both ferromagnetic and antiferromagnetic interactions are discussed.

Abstract

The magnetic lattice of mixed-valence Mn ions in La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ is selectively diluted by partial substitution of Al or Ti for Mn. The ferromagnetic transition temperature $T_\mathrm{c}$ and the saturation magnetization $M_\mathrm{s}$ both decrease with substitution. By presenting the data in terms of selective dilution, $T_\mathrm{c}$ in the low-doping region is found to follow the relation $T_\mathrm{c}=T_\mathrm{c0}(1-n_\mathrm{p})$, where $T_\mathrm{c0}$ refers to the undiluted system and $n_\mathrm{p}$ is the dilution concentration defined as $n_\mathrm{p}=x/0.7$ or $n_\mathrm{p}=x/0.3$ for $M^\prime=$ Al or Ti, respectively. The scaling behavior of $T_\mathrm{c}(n_\mathrm{p})$ can be analyzed in the framework of the molecular-field theory and still valid when Mn is substituted by both Al and Ti. The results are discussed with respect to the contributions from ferromagnetic double exchange and other possible antiferromagnetic superexchange interactions coexisting in the material.