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New holographic memory device could improve speech and image recognition.

Researchers at the University of California, Riverside Bourns College of Engineering and the Russian Academy of Sciences have demonstrated a new type of pattern recognition using a 'magnonic' holographic memory device, intended to improve hardware for speech and image recognition.

Magnonics is an emerging field and is broadly concerned with magnetic phenomena connected with spin waves (see below).

Pattern recognition focuses on finding patterns and regularities in data. In this latest research, input patterns are encoded into the phase (timing) of spin waves, which are collective oscillations of spins in magnetic materials.

Spin wave devices are advantageous over their optical counterparts because they are more scalable due to their wavelengths being shorter than light. Also, spin wave devices are compatible with conventional electronic devices and can be integrated within a chip.

The researchers built a prototype eight-terminal device consisting of a magnetic matrix with micro-antennae placed on the periphery of the matrix to excite and detect spin waves. The principle of operation is based on the effect of spin wave interference, which is similar to the operation of optical holographic devices.

The spin waves propagate through the magnetic matrix and interfere. Some of the input phase patterns produce high output voltage, and other combinations results in a low output voltage, where 'high' and 'low' are defined regarding the reference voltage (ie. output is high if the output voltage is higher than 1 millivolt, and low if the voltage is less than 1 millivolt).

It takes about 100 nanoseconds for recognition, which is the time required for spin waves to propagate and to create the interference pattern.

So far the experimental data collected for several magnonic matrixes show that unique output signatures correspond to specific phase patterns.

The micro-antenna allow the researchers to generate and recognise any input phase pattern, which is a big advantage over existing practices.

According to the researchers, the most appealing property of this approach is that all of the input ports operate in parallel. It takes the same amount of time to recognise patterns (numbers) from 0 to 999, and from 0 to 10,000,000. Potentially, magnonic holographic devices can be fundamentally more efficient than conventional digital circuits. Additionally they may also provide a higher storage density compared to optical counterparts. This is due to a shorter wavelength and their compatibility with conventional electronic devices

Whilst holography has also been touted as a future data storing technology with unprecedented data storage capacity, the main challenge associated with magnonic holographic memory is the scaling of the operational wavelength. This requires the development of sub-micrometer scale elements for spin wave generation and detection.

This research was supported in part by: the Center for Function Accelerated NanoMaterial Engineering (FAME), which is funded with $35 million from the Semiconductor Research Corporation (SRC), a consortium of semiconductor industry companies; the Defense Advanced Research Projects Agency; and the National Science Foundation under the NEB2020 Grant ECCS-1124714. journal/apl/106/14/10.1063/1.4917507

Caption: Prototype device.

Caption: Schematic of an eight-terminal magnonic holographic memory prototype.


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Publication:Holography News
Date:Sep 1, 2015
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