Direct-current voltages in (Ga,Mn)As structures induced by ferromagnetic resonance

Area of Science:

• Spintronics
• Condensed Matter Physics
• Materials Science

Background:

• Spin pumping generates pure spin currents in ferromagnetic/non-magnetic layers, leading to voltage via the inverse spin Hall effect.
• Ferromagnetic resonance also induces voltage in ferromagnetic layers through galvanomagnetic effects.
• Accurate determination of the spin Hall angle relies on distinguishing these voltage sources.

Purpose of the Study:

• To develop and demonstrate a method for separating DC voltages originating from spin pumping/inverse spin Hall effect and galvanomagnetic effects.
• To highlight the critical importance of this separation for accurate spin Hall angle measurements.
• To utilize (Ga,Mn)As/p-GaAs as a model system exhibiting significant galvanomagnetic effects.

Main Methods:

• Employing ferromagnetic resonance to induce magnetization dynamics.
• Utilizing the (Ga,Mn)As/p-GaAs heterostructure as a model system.
• Developing a technique to differentiate voltage signals based on their physical origins.

Main Results:

• A method was successfully established to separate voltages arising from spin pumping and galvanomagnetic effects.
• The (Ga,Mn)As/p-GaAs system demonstrated significant contributions from galvanomagnetic effects.
• Failure to account for galvanomagnetic effects can inflate spin Hall angle values by up to a factor of 8.

Conclusions:

• Accurate measurement of the spin Hall angle necessitates the separation of DC voltages from spin pumping and galvanomagnetic phenomena.
• The developed method provides a critical tool for reliable characterization of spintronic materials.
• This work underscores the need for careful consideration of all contributing effects in complex magnetic heterostructures.