Extreme magnetoresistance in magnetic rare-earth monopnictides

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 WTe₂ and rare-earth monopnictide La(Sb,Bi), these systems tend to be nonmagnetic, 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 1.6×10⁶% at fields of 9 T whereas the magnetoresistance itself is nonmonotonic across the various magnetic phases and shows a transition from negative magnetoresistance to XMR with fields above magnetic ordering temperature T[subscript N]. The magnitude of the XMR is larger than in other rare-earth monopnictides including the nonmagnetic members and follows a nonsaturating 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.Gordon and Betty Moore Foundation (Grant GBMF3848)National Science Foundation (U.S.) (Grant DMR-1554891)United States. Army Research Office (Grant W911NF-16-1-0034)National Science Foundation (U.S.) (Grant DMR-1231319