A Comparative Study Of Spin Hall Magnetoresistance In Fe2o3-Based Systems

Spin Hall magnetoresistance (SMR) provides a unique opportunity for the signal readout of magnetic ordering, especially for magnetic insulators. However, the magnitude of SMR signals is quite small, generally lower than one in a thousand, which is a persistent challenge in the field of spintronics. Here, we investigate SMR at room temperature in alpha -Fe2O3/Pt and gamma -Fe2O3/Pt bilayers as well as the alpha -Fe2O3/Pt/gamma -Fe2O3 trilayer, where alpha -Fe2O3 and gamma -Fe2O3 are antiferromagnetic and ferrimagnetic materials, respectively. In contrast to the positive SMR in the gamma -Fe2O3/Pt bilayer, an unprecedentedly large negative SMR with the magnitude of similar to 0.35% is observed in the alpha -Fe2O3/Pt bilayer due to the spin-flop. The alpha -Fe2O3/Pt/gamma -Fe2O3 trilayer shows features of a combination of positive and negative SMR. A comparative study of SMR in the Fe2O3 family not only enriches spin physics, but also makes Fe2O3 a versatile candidate in spintronic devices.