Random telegraph noise in magnetically driven garnets

Both the length scale and the magnetic field strength dependence of the magnetic noise in ac magnetically driven garnets were measured optically using the Faraday effect. At fields in a limited region, roughly twice the coercive field, the noise exhibits a Lorentzian power spectral density (PSD) consistent with random telegraph noise (RTN). The RTN onset as a function of applied field is rather abrupt and then decreases slowly with further increases in the applied field. The PSD of the noise in the lowest and highest magnetic field regimes is white background noise and is about two decades smaller than that of the RTN. In the field regime of the RTN, the PSD is Lorentzian at all measured length scales. As the measurement length scale increases past the order of a few microns, the low-frequency plateau of the Lorentzian PSD diminishes with increasing area measured as expected for a collection of uncorrelated RTN oscillators with similar characteristic frequencies.