Origin of Orientation-Controlled Magnetoresistance Anisotropy in Topologically Protected Semimetal Bi Films

Topological semimetallic materials have been widely studied in low-dissipation electron transport and spintronics due to the potential spintronic topology. Current analysis in the electromagnetic transport of the topological semimetals focuses on single-crystal films. In this work, the growth characteristics and magnetoresistance effect on topological semimetal polycrystalline Bi are reported. Experimental results show that polycrystalline Bi films contain high-quality crystallinity, preferred orientation out of plane, and random orientation in plane. Moreover, the preferred orientation reveals the transport phenomenon and origin of magnetoresistance anisotropy in polycrystalline Bi films. In particular, Bi films grown in the coexisting (003) and (012) orientations show a negative magnetoresistance change trend at low temperatures. Therefore, this work provides a strategy to control the magnetoresistance anisotropy and the abnormal Hall effect in polycrystalline films.