Electrical detection of ferromagnetic resonance in bulk YIG sample covered with a layer of silver paint

Abstract

We studied the electrical impedance of a bulk polycrystalline YIG sample at room temperature as a function of varying dc magnetic field ( H) and frequency of the microwave (MW) signal ( f = 0.9 GHz to 3 GHz) using a single port impedance analyzer. As the YIG sample is an insulator, silver paint was coated on the top surface and the two ends of the sample to allow the MW current to flow between the signal line and ground plane. While H is swept from -5.2 kOe to +5.2 kOe, a sharp peak in resistance and a dip in reactance appear at a specific value of field H = ± H r. The amplitude of the peak in resistance and the value of H r increase with frequency of the MW signal. The positive magnetoresistance at the peak is 2300% for 3 GHz. Similar but sharp features were also detected in YIG thin films coated with Ag-paint. We attribute these features in magnetoimpedance to Oersted field-induced ferromagnetic resonance in the underneath YIG sample.