Bipolar Magnetic Semiconductors: A New Class of Spintronics Materials

TL;DR

This paper introduces bipolar magnetic semiconductors (BMS), a new class of materials enabling electrical control of spin polarization for spintronics applications, demonstrated through theoretical calculations on carbon nanotubes.

Contribution

It proposes the concept of BMS with reversible spin polarization controlled by gate voltage, supported by band structure and transport calculations.

Findings

BMS materials exhibit opposite spin polarization in valence and conduction bands.

Electrical control of spin polarization is achievable in BMS.

Theoretical confirmation of BMS existence in semi-hydrogenated carbon nanotubes.

Abstract

Electrical control of spin polarization is very desirable in spintronics, since electric field can be easily applied locally in contrast with magnetic field. Here, we propose a new concept of bipolar magnetic semiconductor (BMS) in which completely spin-polarized currents with reversible spin polarization can be created and controlled simply by applying a gate voltage. This is a result of the unique electronic structure of BMS, where the valence and conduction bands possess opposite spin polarization when approaching the Fermi level. Our band structure and spin-polarized electronic transport calculations on semi-hydrogenated single-walled carbon nanotubes confirm the existence of BMS materials and demonstrate the electrical control of spin-polarization in them.