MIT researchers develop new method to control ferromagnets

In principle, ferromagnetic materials should be able to produce faster data storage or logic circuits than today’s conventional ferromagnets, and be able to pack more data into a given space.

But so far, there has been no easy, fast and reliable way to switch the orientation of these magnets to flip from 0 to 1 in a data storage device.

Researchers at MIT and elsewhere have developed a way to quickly switch the poles of a ferromagnet by 180 degrees using just a small applied voltage.

The discovery could usher in a new era of ferromagnetic logic and data storage devices, the researchers said.

The findings have been published in the journal Nature Nanotechnology. The new system uses a thin film of a material called gadolinium cobalt, which belongs to a class of materials known as rare-earth transition metal ferromagnets.

In it, the two elements form an interdigitated lattice of atoms, and the gadolinium atoms preferentially align their magnetic axes in one direction, while the cobalt atoms point in the opposite direction. The balance of the two in the alloy composition determines the overall magnetization of the material.

But the researchers found that by using an electrical voltage to split water molecules into oxygen and hydrogen along the surface of the film, the oxygen could be expelled, while the hydrogen atoms, or more precisely their cores, the single protons, could penetrate deep into the material. Changed the balance of magnetic orientation.

This change is enough to turn the net magnetic field direction 180 degrees, exactly the kind of complete reversal required for devices such as magnetic memory. Because the change is only done by changing the voltage, rather than applying the current, which causes heating that wastes energy through heat dissipation, the process is very energy efficient.

The researchers found that the process of pumping hydrogen nuclei into the material turned out to be very benign. It turns out that for these films, because the proton is such a small entity, it can penetrate most of the material without causing the kind of structural fatigue that leads to failure.

This stability has been proven through rigorous testing. The material survived 10,000 polarity reversals without any sign of degradation.

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