Electrical Control and Readout of Magnetization using Low-Symmetry Topological Semimetals

  Electrical control and detection of magnetization in spintronic devices form the corner stone of integrating magnetic materials into modern technology. By interfacing a magnetic  material with a spin source material, spin-orbit torques can efficiently switch the magnetic  state at high speeds. Moreover, interface-induced magnetoresistive effects offer a pathway for  magnetic detection and fundamental understanding. However, conventional spin source ma terials, constrained by high crystal symmetry, had long assumed certain forms of spin-orbit  torques and magnetoresistive effects to be forbidden. The emergence of two-dimensional ma terials, with their lower crystal symmetry, provides a promising platform for overcoming these  limitations. Their atomic sharp interfaces, flexibility in combining materials with different  crystal structures, and electric tunability make them highly desirable for exploring spin related physics at interfaces. In this thesis, I investigate spin-orbit torque-induced magnetic  switching and novel magnetoresistive effects in bilayer systems comprising a magnetic layer  and a low-symmetry topological semimetal: tungsten ditelluride. Through magnetotrans port studies, I demonstrate unique field-free spin-orbit torque switching of a perpendicular  magnet driven by unconventional out-of-plane spin generation. Additionally, I explore novel  magnetoresistive effects suitable for magnetic detection in innovative device geometries. The  experimental findings in this thesis pave the way for the utilization of low-symmetry spin  source materials in advancing the control and detection of magnetic materials.