Giancarlo Consolo

Micromagnetic simulations using Graphics Processing Units

The methodology for adapting a standard micromagnetic code to run on graphics processing units (GPUs) and exploit the potential for parallel calculations of this platform is discussed. GPMagnet, a general purpose finite-difference GPU-based micromagnetic tool, is used as an example. Speed-up factors of two orders of magnitude can be achieved with GPMagnet with respect to a serial code. This allows for running extensive simulations, nearly inaccessible with a standard micromagnetic solver, at reasonable computational times.

Direct observation of a propagating spin wave induced by spin-transfer torque

Spin torque oscillators with nanoscale electrical contacts are able to produce coherent spin waves in extended magnetic films, and offer an attractive combination of electrical and magnetic field control, broadband operation, fast spin-wave frequency modulation, and the possibility of synchronizing multiple spin-wave injection sites. However, many potential applications rely on propagating (as opposed to localized) spin waves, and direct evidence for propagation has been lacking. Here, we directly observe a propagating spin wave launched from a spin torque oscillator with a nanoscale electrical contact into an extended Permalloy (nickel iron) film through the spin transfer torque effect. The data, obtained by wave-vector-resolved micro-focused Brillouin light scattering, show that spin waves with tunable frequencies can propagate for several micrometres. Micromagnetic simulations provide the theoretical support to quantitatively reproduce the results.

Experimental evidence of self-localized and propagating spin wave modes in obliquely magnetized current-driven nanocontacts.

Through detailed experimental studies of the angular dependence of spin wave excitations in nanocontact-based spin-torque oscillators, we demonstrate that two distinct spin wave modes can be excited, with different frequency, threshold currents, and frequency tunability. Using analytical theory and micromagnetic simulations we identify one mode as an exchange-dominated propagating spin wave, and the other as a self-localized nonlinear spin wave bullet. Wavelet-based analysis of the simulations indicates that the apparent simultaneous excitation of both modes results from rapid mode hopping induced by the Oersted field.

Nonlinear frequency and amplitude modulation of a nanocontact-based spin-torque oscillator

We study the current-controlled modulation of a nanocontact spin-torque oscillator. Three principally different cases of frequency nonlinearity (d(2)f/dI(dc)(2) being zero, positive, and negative) ...

Power and linewidth of propagating and localized modes in nanocontact spin-torque oscillators

The integrated power and linewidth of a propagating and a self-localized spin-wave mode excited by spin-polarized current in an obliquely magnetized magnetic nanocontact are studied experimentally ...

Oscillatory transient regime in the forced dynamics of a nonlinear auto oscillator

We demonstrate that the forced transient dynamics of a nonlinear (nonisochronous) auto-oscillator is qualitatively different from the dynamics of a quasilinear oscillator described by the classical Adlers model. If the normalized amplitude

Combined Frequency-Amplitude Nonlinear Modulation: Theory and Applications

\ensuremath{\mu}

Magnetization dynamics driven by the combined action of ac magnetic field and dc spin-polarized current

of the driving force exceeds a certain critical value

Boundary Conditions for Spin-Wave Absorption Based on Different Site-Dependent Damping Functions

{\ensuremath{\mu}}_{cr}

About identification of Scalar Preisach functions of soft magnetic materials

, the transition to the synchronized regime becomes oscillatory with a frequency proportional to