Magnetization switching using topological surface states.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Spintronics

Background:

• Topological surface states (TSSs) in topological insulators are predicted to generate spin-orbit torques capable of switching adjacent ferromagnets.
• Conductive ferromagnets can suppress TSSs, hindering this effect, whereas insulating ferromagnets are expected to preserve it.

Purpose of the Study:

• To investigate TSS-induced magnetization switching in a topological insulator (Bi₂Se₃) and an insulating ferromagnet (BaFe₁₂O₁₉) heterostructure.
• To characterize the efficiency and temperature dependence of the switching process.

Main Methods:

• Fabrication of a Bi₂Se₃/BaFe₁₂O₁₉ bilayer.
• Application of charge currents in Bi₂Se₃ to induce magnetization switching in BaFe₁₂O₁₉.
• Measurement of magnetization switching fields and efficiency at varying temperatures.

Main Results:

• Demonstrated charge current-induced switching of magnetization in BaFe₁₂O₁₉.
• Observed a significant reduction of ~4000 Oe in the switching field when a current was applied.
• Reported a switching efficiency at 3 K that is 300 times higher than at room temperature and 30 times higher than in Pt/BaFe₁₂O₁₉.

Conclusions:

• The study confirms TSS-induced magnetization switching in an insulating ferromagnet heterostructure.
• Enhanced low-temperature performance is attributed to more pronounced TSSs, increased surface conductivity, and reduced bulk conductivity.
• The findings highlight the potential of topological insulators for efficient spintronic applications.