Researchers in China have fabricated a new hybrid superconducting device from a special type of material known as an artificial spin ice (ASI). The innovative structure, which is made of asymmetric nanomagnets, could be used to build magnetic-field-driven superconducting diodes for use in energy-efficient electronics.
ASIs get their name from the fact that at low temperatures, their magnetic moments adopt the same disordered pattern typified by proton spins in water ice. They have a tetrahedral structure, with rare-earth ion moments occupying the corners in a way that obeys the so-called “ice rules”: two of the moments point into the tetrahedron, while two point out of it. In this configuration, the moments are unable to align, and the material is said to be geometrically frustrated.
The behaviour of the new ASI-based device is driven by a phenomenon known as the magnetic nonreciprocal effect, in which a material displays zero resistance along the direction of an applied magnetic field while continuing to have resistance in the opposite direction. “This is analogous to the behaviour of a superconducting diode and is a recently-discovered effect that is creating a flurry of interest in the field,” explains Yong-Lei Wang of Nanjing University, who led the research.
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