OBSERVATION OF NONLINEAR FMR IN AMORPHOUS MICROWIRES USING STANDARD X-BAND SPECTROMETER
Experimental technique for investigation of nonlinear ferromagnetic resonance in thin metallic wires is described. It uses a simple home-made X-band FMR spectrometer with static magnetic field and microwave electric field parallel to the wire. Elec-tric polarization of the wire induces microwave current and large circumferential AC magnetic field on the wire surface. This re-duces the critical power for the onset of nonlinear effects. Moreover, in Fe-rich amorphous metals the condition of coincidence of the main and the subsidiary resonances is satisfied at X-band frequencies which further reduces the critical field for the on-set of instability. Then the microwave power of few mW is sufficient for observation of nonlinear FMR. The nonlinear reso-nance curves of very thin wires show well distinguished fine structure with the period inversely proportional to the wire diame-ter. The observed phenomenon is explained by the parametric excitation of dipole-exchange resonance modes of a long circular cylinder.
Keywords: ferromagnetic resonance, amorphous microwires, nonlinear phenomena, spin waves