# Extreme Magnetoresistance in Magnetic Rare Earth Monopnictides

## TL;DR

This paper investigates how magnetic order influences extreme magnetoresistance (XMR) in magnetic rare earth monopnictides, revealing that magnetic phases significantly modulate XMR magnitude and behavior, with CeSb showing exceptionally large and non-saturating XMR.

## Contribution

It demonstrates the modulation of XMR by magnetic order in magnetic rare earth monopnictides, highlighting the role of orbital states and magnetic phases in controlling magnetoresistance.

## Key findings

- CeSb exhibits XMR over 1.6 million percent at 9 T.
- Magnetoresistance in CeSb is non-monotonic across magnetic phases.
- XMR follows a non-saturating power law above 30 T.

## Abstract

The acute sensitivity of the electrical resistance of certain systems to magnetic fields known as extreme magnetoresistance (XMR) has recently been explored in a new materials context with topological semimetals. Exemplified by WTe$_{2}$ and rare earth monopnictide La(Sb,Bi), these systems tend to be non-magnetic, nearly compensated semimetals and represent a platform for large magnetoresistance driven by intrinsic electronic structure. Here we explore electronic transport in magnetic members of the latter family of semimetals and find that XMR is strongly modulated by magnetic order. In particular, CeSb exhibits XMR in excess of $1.6 \times 10^{6}$ % at fields of 9 T while the magnetoresistance itself is non-monotonic across the various magnetic phases and shows a transition from negative magnetoresistance to XMR with field above magnetic ordering temperature $T_{N}$. The magnitude of the XMR is larger than in other rare earth monopnictides including the non-magnetic members and follows an non-saturating power law to fields above 30 T. We show that the overall response can be understood as the modulation of conductivity by the Ce orbital state and for intermediate temperatures can be characterized by an effective medium model. Comparison to the orbitally quenched compound GdBi supports the correlation of XMR with the onset of magnetic ordering and compensation and highlights the unique combination of orbital inversion and type-I magnetic ordering in CeSb in determining its large response. These findings suggest a paradigm for magneto-orbital control of XMR and are relevant to the understanding of rare earth-based correlated topological materials.