Ferromagnetic resonance in copper-permalloy point contacts

Abstract

The response of copper-permalloy (Ni 80 Fe 20 ) point microcontacts to microwave irradiation (8-12 GHz) is investigated systematically. The effects of the external magnetic field strength, transport current flowing through the contact, and microwave intensity and frequency on the measured signal are studied. The contributions to the contact electrical resistance owing to giant and anisotropic magnetoresistance are analyzed. The experimentally determined positions of the resonance features are in good agreement with Kittel's formula for FMR in films in parallel magnetic fields. The resonance signal is observed against the background of an additional contribution owing to rectification of the rf field on the nonlinear current-voltage characteristic of the contact. Two mechanisms for the resonance response are discovered: synchronous selfdetection from mixing of the rf current with temporal variations in the resistance and a bolometric response associated with the steady-state variation in the contact resistance when magnetization precession is excited. The amplitude of the resonance signal is linearly proportional to the transport current through the contact and to the intensity of the microwave irradiation. V C 2014 AIP Publishing LLC. [http://dx.

Homodyne-detected ferromagnetic resonance of in-plane magnetized nanocontacts: Composite spin-wave resonances and their excitation mechanism

“…In the NC geometry literature 7,[12][13][14][15]28 , the observed ST-FMR spectra of the NiFe-based free layers have been analyzed as a single resonance, despite a significant peak asymmetry hinting at additional contributions. The linewidth of this asymmetric peak has not been understood so far 7 .…”