title: Decoherence and mode hopping in a magnetic tunnel junction based spin torque oscillator.
abstract: We discuss the coherence of magnetic oscillations in a magnetic tunnel junction based spin torque oscillator as a function of the external field angle. Time-frequency analysis shows mode hopping between distinct oscillator modes, which arises from linear and nonlinear couplings in the Landau-Lifshitz-Gilbert equation, analogous to mode hopping observed in semiconductor ring lasers. These couplings and, therefore, mode hopping are minimized near the current threshold for the antiparallel alignment of free-layer with reference layer magnetization. Away from the antiparallel alignment, mode hopping limits oscillator coherence.
authors.affiliation: Physics Department, University of Gothenburg, 41296 Gothenburg, Sweden.
authors.forename: P K
authors.initials: PK
authors.lastname: Muduli
authors.forename: O G
authors.initials: OG
authors.lastname: Heinonen
authors.forename: Johan
authors.initials: J
authors.lastname: Akerman