New ‘magnonic’ holographic memory device could improve speech and image recognition

May 14, 2015

Clockwise, photo of the prototype device, schematic of an eight-terminal magnonic holographic memory prototype, and s collection of experimental data obtained for two magnonic matrices (credit: A. Kozhevnikov et al./Applied Physics Letters)

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.

The device is based on patterns of sound and images that are encoded into the phase (timing) of spin waves, which are collective oscillations of spins in magnetic materials. Spin wave devices have a shorter wavelength than light, so they are more scalable. Spin-wave devices are also compatible with conventional electronic devices and can be integrated into a chip.

The researchers built a prototype eight-terminal device consisting of a magnetic matrix with microantennas to excite and detect the spin waves. The microantennas allow the researchers to generate and recognize input phase patterns, an advantage over existing designs. Another advantage of this approach is that all of the input ports operate in parallel, so the devices could be more efficient than conventional digital circuits.

The work builds upon findings published last year by the researchers, who showed a 2-bit magnonic holographic memory device can recognize internal magnetic memory states via spin wave superposition. That work was recognized as a top 10 physics breakthrough by Physics World magazine.

The new findings were published in a paper in the journal Applied Physics Letters.

The 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.

Abstract of Pattern recognition with magnonic holographic memory device 

In this work, we present experimental data demonstrating the possibility of using magnonic holographic devices for pattern recognition. The prototype eight-terminal device consists of a magnetic matrix with micro-antennas 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. Input information is encoded in the phases of the spin waves generated on the edges of the magnonic matrix, while the output corresponds to the amplitude of the inductive voltage produced by the interfering spin waves on the other side of the matrix. The level of the output voltage depends on the combination of the input phases as well as on the internal structure of the magnonic matrix. Experimental data collected for several magnonic matrixes show the unique output signatures in which maxima and minima correspond to specific input phase patterns. Potentially, magnonic holographic devices may provide a higher storage density compare to optical counterparts due to a shorter wavelength and compatibility with conventional electronic devices. The challenges and shortcoming of the magnonic holographic devices are also discussed.