A low-field temperature-dependent EPR signal in terraced MgO:Mn2+ nanoparticles: an enhanced Zeeman splitting in the wide-bandgap oxide

TL;DR

This study investigates how surface defects in terraced MgO:Mn2+ nanoparticles influence their electronic properties, revealing a novel temperature-dependent EPR signal linked to enhanced Zeeman splitting and charge carriers at structural defects.

Contribution

It introduces the observation of a new EPR feature in terraced MgO:Mn2+ nanoparticles caused by surface defects and exchange interactions, expanding understanding of defect-related electronic behavior.

Findings

Discovery of a non-monotonous temperature-dependent EPR shift.

Identification of surface defects influencing charge carrier behavior.

Evidence of enhanced Zeeman splitting due to structural defects.

Abstract

Mn2+ ion doping is used as an electron paramagnetic resonance (EPR) probe to investigate the influence of low-coordination structural defects such as step edges at the surface of terraced (001) MgO nanoparticles on the electronic properties. Beside the well-known hyperfine sextet of Mn2+ ions in the cubic crystal field of MgO, an additional EPR feature with a striking non-monotonous temperature dependent shift of the g-factor is observed in terraced nanoparticles in the temperature range from 4K to room temperature. By linking the difference in the temperature dependence of the Mn2+ sextet intensity in cubic and terraced nanoparticles with the possible s-d exchange shift and enhanced Zeeman splitting we conclude that the novel EPR feature originates from the loosely trapped charge-compensating carriers at the abundant structural defects at the surface of terraced nanoparticles due to their exchange interaction with neighboring Mn2+ ions.