Bifurcation and chaos in spin-valve pillars in a periodic applied magnetic field

Abstract

We study the bifurcation and chaos scenario of the macro-magnetization vector in a homogeneous nanoscale-ferromagnetic thin film of the type used in spin-valve pillars. The underlying dynamics is described by a generalized Landau-Lifshitz-Gilbert (LLG) equation. The LLG equation has an especially appealing form under a complex stereographic projection, wherein the qualitative equivalence of an applied field and a spin-current induced torque is transparent. Recently chaotic behavior of such a spin vector has been identified by Zhang and Li using a spin polarized current passing through the pillar of constant polarization direction and periodically varying magnitude, owing to the spin-transfer torque effect. In this paper we show that the same dynamical behavior can be achieved using a periodically varying applied magnetic field, in the presence of a constant DC magnetic field and constant spin current, which is technically much more feasible, and demonstrate numerically the chaotic dynamics in the system for an infinitely thin film. Further, it is noted that in the presence of a nonzero crystal anisotropy field chaotic dynamics occurs at much lower magnitudes of the spin-current and DC applied field.

8 pages, 7 figures. To appear in Chaos

References in corpus (4)

• Excitations of incoherent spin-waves due to spin-transfer torque
• Spin-Torque Driven Magnetization Dynamics: Micromagnetic Modelling
• Chaotic Dynamics of Spin-Valve Oscillators
• Chaotic Spin Dynamics of a Long Nanomagnet Driven by a Current

Cited by in corpus (6)

• The Fascinating World of Landau-Lifshitz-Gilbert Equation: An Overview
• Chimera and globally clustered chimera: Impact of time delay
• Synchronization of an array of spin torque nano oscillators in periodic applied external magnetic field
• Enhanced synchronization in an array of spin torque nano oscillators in the presence of oscillating external magnetic field
• Tunable Transient Decay Times in Nonlinear Systems: Application to Magnetic Precession
• Synchronization and chaos in spin-transfer-torque nano-oscillators coupled via a high speed Op Amp