1：Experimental Design and Method Selection:

The study uses an experimental setup to measure transmission of visible light through magnetic nanogranular films as a function of the angle between the magnetic field direction and the incident light direction, with a fixed magnetic field strength of 400 Oe. The method involves rotating an electromagnet to vary the angle θ from 0° to 45° while keeping the light beam perpendicular to the sample surface.

2：Sample Selection and Data Sources:

Samples are Cox-(Al2O3)100-x thin films with Co compositions x = 10, 15, 25, 35, 40, and 45 at.%, deposited on glass substrates using radio-frequency co-sputtering. Thickness is about 90-100 nm, determined by an IQ Alpha-Step profilometer. Co composition is verified by X-ray energy dispersive spectroscopy (EDS).

3：List of Experimental Equipment and Materials:

Equipment includes a visible white light source, lenses, monochromator (selected wavelengths 560-695 nm), chopper, polarizer, analyzer, sample holder, electromagnet (field strength 400 Oe), CdS photodetector, and lock-in amplifier (DSP 7225). Materials include Co and Al2O3 targets for sputtering, argon gas, and glass substrates.

4：5). Materials include Co and Al2O3 targets for sputtering, argon gas, and glass substrates. Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: The sample is placed in the electromagnet center. The magnetic field direction is rotated to vary θ, and transmission intensity is measured for different wavelengths. Transmission ratio T(θ) = JT(400 Oe)/JT(0 Oe) is calculated, where JT is the transmitted light intensity measured by the photodetector and lock-in amplifier.

5：Data Analysis Methods:

Data is analyzed to observe dependencies on θ, H, x, and λ, attributing behaviors to photon-magnon interactions, with interpretations based on plasmonic spin mechanisms and resonant conditions.