Spin wave Brillouin measurements in FeCo with a virtually imaged phased array spectrometer

Area of Science:

• Condensed Matter Physics
• Materials Science
• Spectroscopy

Background:

• Spin waves are fundamental excitations in magnetic materials, crucial for developing advanced spintronic devices.
• Brillouin spectroscopy is a key technique for probing spin waves, but often limited by acquisition speed and signal-to-noise ratio.
• Efficient characterization of magnonic devices requires advanced spectroscopic methods.

Purpose of the Study:

• To demonstrate the first efficient acquisition of spin wave Brillouin spectra using a virtually imaged phase array (VIPA) spectrometer.
• To characterize thermally excited magnons in a Fe75Co25 thin film with high spectral resolution and signal-to-noise ratio.
• To assess the suitability of VIPA-based instrumentation for imaging spin wave propagation in magnonic devices.

Main Methods:

• Utilized a virtually imaged phase array (VIPA) spectrometer combined with an etalon-based notch filter.
• Acquired Brillouin spectra of thermally excited magnons in a 5 nm epitaxially grown single-crystalline Fe75Co25 film.
• Applied external magnetic fields from 29 to 370 mT and mapped spatial variations in a non-uniform field.

Main Results:

• Achieved efficient spin wave Brillouin spectra acquisition with rapid detection (100 ms) and high signal-to-noise ratio (>100 in 10 s).
• Obtained a spectral resolution of 0.45 GHz at a pump power of 23 mW.
• Estimated the effective magnetization of the Fe75Co25 film to be 1.6 ± 0.1 MA/m.
• Generated a 2D map of Brillouin shift variation, showcasing spatial imaging capabilities.

Conclusions:

• The VIPA-based spectrometer enables highly efficient and sensitive acquisition of spin wave Brillouin spectra.
• This technique provides a powerful tool for characterizing magnetic materials and magnonic devices.
• VIPA instrumentation is suitable for real-time imaging of spin wave propagation in complex magnetic systems.