SPINTORQOSC

Spin torque oscillators with applications in non digital computing science and communications

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 Obiettivo del progetto (Objective)

'The project aims at studying spin-wave excitations from nanocontacts and implementing biological inspired computations with wavefronts in nano-structures, likely in terms of spin waves in ferromagnetic films. This implies building a bridge between Mathematical Neuroscience and Applied Physics. It is also of great importance to create a new research line at the emph{Magnetics Laboratory Group} at UB with Prof. J. Tejada and Dr. J. M. Hernandez based on nanofabrication of magnetic devices sensors in order to study gyromagnetic phenomena and the patterning of spin dynamics at the quantum level. Nanoscale, current controlled spin-torque oscillators (STOs) are of great fundamental interest and also of interest for signal processing and communication, including on-chip communication via spin-wave propagation. However, the fundamental characteristics of the spin-waves emitted by STOs are unknown. STOs, consisting of a point contact to a thin film ferromagnet (FM), were first proposed theoretically in 1996. High DC current densities generate a high-frequency dynamic response (up to 100 GHz) in the FM layer and can result in the emission of spin-waves. Studies of STOs to date have relied primarily on electronic transport characteristics. Further studies have shown these oscillations may be phase-locked to an external rf source, via a process known as injection locking, providing a means of conducting time-resolved spatial imaging. The aim of the proposed work is to study the fundamental characteristics of spin-waves generated from STOs using full-field transmission x-ray microscopy (TXM), combined with x-ray magnetic circular dichronism (XMCD) to provide magnetic contrast. We will determine the physical requirements for implementation with STO’s of a novel computational framework based on polychronous wavefront dynamics using temporal and spatial patterns of activity in pulse-propagating media.'

Introduzione (Teaser)

Oscillating magnetisation waves have great potential for memory and information processing. EU-funded scientists studied and exploited them in biology-inspired models, experimental systems and devices.

Descrizione progetto (Article)

Spin torque oscillators (STOs) are novel nano-scale oscillating devices based on spintronics technology and periodic flipping of magnetisation. Their tiny scale and high tunability make them very attractive for many applications, including the non-conventional. However, mechanisms are still poorly understood and understanding is a prerequisite for exploitation.

EU-funded scientists initiated the project 'Spin torque oscillators with applications in non digital computing science and communications' (SPINTORQOSC) to enhance knowledge and facilitate implementation of biologically inspired computations in nanostructures. The focus was on spin wave excitations in ferromagnetic thin films, a phenomenon supporting new types of information processing.

The team set out to implement wave front computations using spin waves analogous to computations by the brain exploiting periodic electrical oscillatory activity. Spin waves or magnons are elementary collective excitations of spins, where spin is the angular momentum inherent to all elementary particles. In STOs, very large magnitude magnetisation oscillations are maintained.

Theoretical work led to achievement of the first goal and publications of a model for implementing biologically inspired computations with wave fronts in nanostructures. Scientists proposed a concept consisting of ferromagnetic thin films where the spin waves propagate and nanocontacts (the STOs) that contact the films and excite magnetisation dynamics. Thus, the STOs both create spin wave patterns and, at the same time, sense incoming spin waves.

Experimental work led to fabrication of STO devices on ferromagnetic thin films and demonstration of spin wave activity in them measured electrically. The team has also investigated various methods for imaging and controlling the spin waves, including the use of two different synchrotrons and the use of organic semiconductors.

Coupling between magnetic thin films and the organic semiconductors led to discovery of a new effect, transduction of a magnetic signal into an optical one via electroluminescence in the organic semiconductor. Other work focused on single-molecule magnets and fabrication of a number of STO devices.

SPINTORQOSC outcomes have been published in numerous papers in prestigious peer-reviewed scientific journals. Through theory and experiment, scientists have deepened understanding of STOs and their mechanisms and control. Exploitation in novel devices is around the corner.