Large linear non-saturating magnetoresistance and high mobility in ferromagnetic MnBi

Yangkun He,Jacob Gayles,Mengyu Yao,Claudia Felser,Vladimir N Strocov,Michael Nicklas,Toni Helm,Gerhard H Fecher,Walter Schnelle,Tommy Reimann,Yan Sun

doi:10.1038/s41467-021-24692-7

Abstract

A large non-saturating magnetoresistance has been observed in several nonmagnetic topological Weyl semi-metals with high mobility of charge carriers at the Fermi energy. However, ferromagnetic systems rarely display a large magnetoresistance because of localized electrons in heavy d bands with a low Fermi velocity. Here, we report a large linear non-saturating magnetoresistance and high mobility in ferromagnetic MnBi. MnBi, unlike conventional ferromagnets, exhibits a large linear non-saturating magnetoresistance of 5000% under a pulsed field of 70 T. The electrons and holes’ mobilities are both 5000 cm2V−1s−1 at 2 K, which are one of the highest for ferromagnetic materials. These phenomena are due to the spin-polarised Bi 6p band’s sharp dispersion with a small effective mass. Our study provides an approach to achieve high mobility in ferromagnetic systems with a high Curie temperature, which is advantageous for topological spintronics.

Highlights

A large non-saturating magnetoresistance has been observed in several nonmagnetic topological Weyl semi-metals with high mobility of charge carriers at the Fermi energy
Its origin lies in the massless Weyl states associated to the linear band crossings at the Fermi energy and a high Fermi velocity
Magnetic topological semimetals allow for the manipulation of the Fermi surface topology by external electromagnetic fields and are fundamental in topological spintronics research

Summary

Introduction

A large non-saturating magnetoresistance has been observed in several nonmagnetic topological Weyl semi-metals with high mobility of charge carriers at the Fermi energy. We find one of the largest mobilities in ferromagnetic materials These phenomena are due to the linear dispersion of the 6p band at the Fermi energy with a small effective mass as confirmed from state-of-the-art first-principle calculations, as well as angle-resolved photoemission spectroscopy (ARPES) and Shubnikov–de Haas (SdH) oscillations experiments on single crystals. In this sense, MnBi with an MR comparable to nonmagnetic semimetals is unique in comparison to the topological ferromagnetic counterparts. A giant MR single crystal device that is tunable purely by the magnetic moment can have far-reaching implications for spintronic devices

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Conclusion