Spin-torque ferromagnetic resonance induced by the spin Hall effect

Area of Science:

• Condensed Matter Physics
• Materials Science
• Spintronics

Background:

• The spin Hall effect (SHE) is a key phenomenon in spintronics, converting charge current into a transverse spin current.
• Understanding spin-charge coupling is crucial for developing novel electronic devices.
• Ferromagnetic resonance (FMR) is a sensitive technique for probing magnetic dynamics.

Purpose of the Study:

• To demonstrate the excitation of magnetic precession in a ferromagnetic film via the spin Hall effect in an adjacent heavy metal film.
• To differentiate the FMR signal generated by the spin current from the Oersted field contribution.
• To establish a quantitative method for determining spin current and spin Hall angle.

Main Methods:

• Fabrication of a platinum/nickel-iron (Pt/NiFe) bilayer thin film.
• Application of alternating current through the Pt layer to generate spin current via SHE.
• Analysis of ferromagnetic resonance (FMR) signals arising from both spin angular momentum transfer and Oersted fields.
• Quantitative analysis of the ratio between the two FMR signals.

Main Results:

• The spin Hall effect in Pt successfully induced magnetic precession in the adjacent NiFe film.
• Two distinct FMR signals were observed, attributable to spin current transfer and Oersted fields, with different symmetries.
• The ratio of these signals provided a quantitative measure of the spin current and the spin Hall angle.

Conclusions:

• The study confirms that the spin Hall effect is an effective mechanism for exciting magnetic dynamics in adjacent ferromagnetic materials.
• The developed method allows for the precise quantification of spin current and spin Hall angle in thin-film heterostructures.
• This work has implications for advanced spintronic device design and characterization.