Letter abstract
Nature Materials 3, 877 - 881 (2004)
doi:10.1038/nmat1237
Subject Categories: Electronic materials | Magnetic materials | Nanoscale materials | Computation, modelling and theory
Excitations of incoherent spin-waves due to spin-transfer torque
Kyung-Jin Lee1,2,3, Alina Deac1,2, Olivier Redon1,2, Jean-Pierre Nozières1 and Bernard Dieny1
The possibility of exciting microwave oscillations in a nanomagnet by a spin-polarized current, as predicted by Slonczewski1 and Berger2, has recently been demonstrated3. This observation opens important prospects of applications in radiofrequency components. However, some unresolved inconsistencies are found when interpreting the magnetization dynamics within the coherent spin-torque model4, 5, 6. In some cases, the telegraph noise caused by spin-currents could not be quantitatively described by that model. This has led to controversy about the need for an effective magnetic temperature model7, 8, 9, 10, 11. Here we interpret the experimental results of Kiselev et al.3 using micromagnetic simulations. We point out the key role played by incoherent spin-wave excitation due to spin-transfer torque. The incoherence is caused by spatial inhomogeneities in local fields generating distributions of local precession frequencies. We observe telegraph noise with gigahertz frequencies at zero temperature. This is a consequence of the chaotic dynamics and is associated with transitions between attraction wells in phase space.
- SPINTEC — Unité de Recherche Associée CEA/DSM & CNRS/SPM-STIC, CEA Grenoble, 38054 Grenoble, France
- CEA/DRT/LETI–CEA/GRE, 17 Rue des Martyrs, 38054 Grenoble, Cedex 9, France
- Permanent address: Storage Laboratory, Samsung Advanced Institute of Technology, Suwon, Korea
Correspondence to: Kyung-Jin Lee1,2,3 e-mail: lee@drfmc.ceng.cea.fr
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