Charge carrier density collapse in La_0.67Ca_0.33MnO_3 and La_0.67Sr_0.33MnO_3 epitaxial thin films

TL;DR

This study investigates how charge carrier density in La_0.67Ca_0.33MnO_3 and La_0.67Sr_0.33MnO_3 thin films drastically decreases at their ferromagnetic transition temperatures, revealing a link between magnetic ordering and electronic properties.

Contribution

First measurement of temperature-dependent Hall resistivity in these manganite thin films showing a charge carrier density collapse at T_C.

Findings

Charge carrier density drops to 0.6 holes per unit cell at T_C

High field Hall measurements reveal a significant carrier density change

Electron-magnon scattering influences resistivity at low temperatures

Abstract

We measured the temperature dependence of the linear high field Hall resistivity of La_0.67Ca_0.33MnO_3 (T_C=232K) and La_0.67Sr_0.33MnO_3 (T_C=345K) thin films in the temperature range from 4K up to 360K in magnetic fields up to 20T. At low temperatures we find a charge carrier density of 1.3 and 1.4 holes per unit cell for the Ca- and Sr-doped compound, respectively. In this temperature range electron-magnon scattering contributes to the longitudinal resistivity. At the ferromagnetic transition temperature T_C a dramatic drop in the number of current carriers $n$ down to 0.6 holes per unit cell, accompanied by an increase in unit cell volume, is observed. Corrections of the Hall data due to a non saturated magnetic state will lead a more pronounced charge carrier density collapse.