Effect of Mn substitution by Ga on the optical properties of a metallic manganite

TL;DR

This study investigates how substituting Mn with Ga in a metallic manganite affects its optical properties and charge dynamics, revealing insights into the metal-insulator transition through infrared reflectivity measurements.

Contribution

It provides a detailed analysis of the optical changes due to Ga substitution in La(2/3)Sr(1/3)MnO(3), introducing a model linking optical parameters to magnetization.

Findings

Ga substitution reduces ferromagnetic order and Jahn-Teller distortion.

The plasma frequency and scattering rate decrease with increasing Ga content.

The model accurately describes the metal-insulator transition behavior.

Abstract

In a metallic manganite like La(2/3)Sr(1/3)MnO(3), the substitution of Mn(+3) by Ga(+3) dilutes the ferromagnetic order and locally cancels the Jahn-Teller distortion, without heavily affecting the crystal structure. One can thus follow the changes in the charge dynamics induced by Ga, until the ferro-metallic manganite is turned into an insulator. Here this phenomenon is studied in detail through the infrared reflectivity of five samples of La(2/3)Sr(1/3)Mn(1-x)Ga(x)O(3), with x increasing from 0 to 0.30 and for 50 < T < 320 K. A simple model which links the measured optical parameters to the magnetization M(x, T) well describes the behavior of the plasma frequency, the scattering rate, and the mid-infrared absorption along the metal-to-insulator transition.