Charge-Induced Spin Torque in Anomalous Hall Ferromagnets

Area of Science:

• Condensed matter physics
• Spintronics
• Materials science

Background:

• Conventional spintronic devices rely on current-induced spin-orbit torque.
• Controlling magnetization without current flow is a key challenge for energy-efficient devices.

Purpose of the Study:

• To demonstrate a novel mechanism for generating spin torque.
• To explore the potential for current-free magnetization switching.
• To investigate charge-induced spin torque in magnetic systems.

Main Methods:

• Phenomenological derivation of spin torque.
• Modeling based on Dirac-Weyl semimetals.
• Experimental demonstration in thin films with gate control.

Main Results:

• Spin-orbit coupled electrons induce spin torque on local magnetization without current.
• Spin torque is proportional to anomalous Hall conductivity and can overcome the Zeeman field.
• Magnetization switching achieved via gate control.

Conclusions:

• Charge-induced spin torque is an equilibrium effect, offering higher efficiency than current-induced methods.
• This mechanism is potentially realizable in various magnetic materials, including doped topological insulators and transition materials.