Electron Paramagnetic Resonance of Mn in Bi$_2$Se$_3$ Topological Insulator

TL;DR

This study uses electron paramagnetic resonance to analyze Mn impurities in Bi$_2$Se$_3$ topological insulators, revealing their electronic states, magnetic properties, and impact on the material's conductivity.

Contribution

It provides detailed characterization of Mn impurity states and magnetic properties in Bi$_2$Se$_3$, highlighting their role in modifying electrical conductivity.

Findings

Mn exists as Mn$^{2+}$ with high-spin S=5/2 in Bi$_2$Se$_3$

Mn acts as an acceptor, reducing electron concentration

The EPR spectrum shows isotropic g-factor and large axial parameter D

Abstract

Electron paramagnetic resonance was used to investigate Mn impurity in Bi$_2$Se$_3$ topological insulator grown by the vertical Bridgman method. Mn in high-spin S = 5/2, Mn$^2$$^+$ configuration, was detected regardless of the conductivity type of the host material. This means that Mn$^2$$^+$(d$^5$) energy level is located within the valence band, and Mn$^1$$^+$(d$^6$) energy level is outside the energy gap of Bi$_2$Se$_3$. The electron paramagnetic resonance spectrum of Mn$^2$$^+$ in Bi$_2$Se$_3$ is characterized by the isotropic g-factor |g| = 1.91 and large axial parameter D = -4.20 GHz x h. This corresponds to the zero-field splitting of the Kramers doublets equal to 8.4 GHz x h and 16.8 GHz x h, respectively, which is comparable to the Zeeman splitting for the X-band. Mn in Bi$_2$Se$_3$ acts as an acceptor, effectively reducing native-high electron concentration, compensating selenium vacancies, and resulting in p-type conductivity.