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Title: Non-linear mode interaction between spin torque driven and damped modes in spin torque nano-oscillators

The influence of dynamic coupling in between magnetic layers of a standard spin torque nano-oscillator composed of a synthetic antiferromagnet (SyF) as a polarizer and an in-plane magnetized free layer has been investigated. Experiments on spin valve nanopillars reveal non-continuous features such as kinks in the frequency field dependence that cannot be explained without such interactions. Comparison of experiments to numerical macrospin simulations shows that this is due to non-linear interaction between the spin torque (STT) driven mode and a damped mode that is mediated via the third harmonics of the STT mode. It only occurs at large applied currents and thus at large excitation amplitudes of the STT mode. Under these conditions, a hybridized mode characterized by a strong reduction of the linewidth appears. The reduced linewidth can be explained by a reduction of the non-linear contribution to the linewidth via an enhanced effective damping. Interestingly, the effect depends also on the exchange interaction within the SyF. An enhancement of the current range of reduced linewidth by a factor of two and a reduction of the minimum linewidth by a factor of two are predicted from simulation when the exchange interaction strength is reduced by 30%. These results openmore » directions to optimize the design and microwave performances of spin torque nano-oscillators taking advantage of the coupling mechanisms.« less
Authors:
; ; ; ;  [1] ;  [2] ;  [2] ;  [3]
  1. Univ. Grenoble Alpes, F-38000 Grenoble (France)
  2. (France)
  3. CEA-LETI, MINATEC, DRT/LETI/DIHS, 38054 Grenoble (France)
Publication Date:
OSTI Identifier:
22399044
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 106; Journal Issue: 19; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ANTIFERROMAGNETIC MATERIALS; ANTIFERROMAGNETISM; COMPARATIVE EVALUATIONS; COUPLING; DAMPING; EXCHANGE INTERACTIONS; EXCITATION; LAYERS; MAGNETIZATION; MICROWAVE RADIATION; NANOSTRUCTURES; NONLINEAR PROBLEMS; OSCILLATORS; SPIN; TORQUE