Magnetoresistance in ferromagnetic materials and related heterostructures plays essential roles both in fundamental understanding of magnetism and electron transport in these structures and in various technological applications. Recently, several new types of magnetoresistance effects of different origins have attracted much attention, which include spin Hall magnetoresistance (SMR) in ferromagnet/heavy metal (FM/HM) bilayers, Rashba-Edelstein magnetoresistance (REMR) in ferromagnet/nonmagnetic metal (FM/NM) heterostructures, and Hanle magnetoresistance (HM) in heavy metals (see illustration below a-c). One key aspect of all these newly observed MR phenomena is that they all originate from a two-step charge-spin conversion process, i.e., in the first step charge current is converted to spin current through either the spin Hall effect or the Rashba-Edelstein effect, and in the second step part of the reflected spin current is converted back to charge current by the respective inverse effects.
We have recently reported on the observation of a new type of magnetoresistance, dubbed anomalous Hall magnetoresistance (AHMR). The AHMR originates from the anomalous Hall effect (AHE) and its inverse (i.e., IAHE). Although it also involves a two-step charge-spin conversion process, unlike the SMR which is typically present in FM/HM bilayers, the AHMR was observed in a single layer of FM. In addition to serving as an important tool for studying spin-charge conversion processes in FM, the AHMR is also promising for spintronics applications as the polarization of the spin current generated by the AHE can be controlled by the magnetization direction.