An Electron Paramagnetic Resonance Study of Electron-Hole Asymmetry in Charge Ordered Pr_1-x Ca_xMnO_3 (x=0.64, 0.36)

TL;DR

This study compares temperature-dependent EPR results of electron- and hole-doped Pr_1-x Ca_xMnO_3, revealing significant differences in magnetic parameters and microscopic interactions related to charge ordering.

Contribution

It provides the first detailed EPR comparison between electron- and hole-doped Pr_1-x Ca_xMnO_3, highlighting contrasting microscopic interactions and charge ordering effects.

Findings

Different `g' values at room temperature for electron and hole doping.

Distinct temperature dependences of EPR parameters in the two systems.

Absence of T_{co} peak in electron-doped EPR asymmetry parameter.

Abstract

We present and compare the results of temperature-dependent electron paramagnetic resonance (EPR) studies on Pr_1-x Ca_xMnO_3 for x = 0.64 which is electron-doped with those on the hole doped x = 0.36 composition. The temperature dependence of the various parameters obtained from the powder and single crystal spectra show significant differences between the two manganites. At room temperature the `g' parameter for the electron doped system is less than the free electron `g' value `g_e', whereas for the hole-doped system it is more than `g_e'. Further, the `g' value and the linewidth obtained from the powder spectra as well as the single crystal spectra show different functional dependences on temperature in the two systems. Quite strikingly, the peak observed at T_{co} in the temperature dependence of the asymmetry parameter, alpha, of the single crystal spectra in the hole-doped system is absent in the electron-doped system. We understand this contrasting behaviour of the EPR parameters in the two systems in terms of very different nature of microscopic interactions in them.