Most magnets shrug off tiny temperature tweaks. But now physicists have created a new nanomaterial that dramatically changes how easily it flips its magnetic orientation when heated or cooled only slightly. The effect, never before seen in any material, could eventually lead to new types of computer memory.
Materials become magnetized when their internal magnetic grains, which usually point in different directions, align in a strong enough magnetic field. How much a material’s grains resist aligning is known as its coercivity. A familiar bar magnet, for example, has high coercivity, with its typically constant north-south poles. Other substances, such as iron and nickel, have low coercivity, meaning they can change their orientations more easily.
Coercivity isn’t just about a magnet’s composition: It also depends on its temperature. Usually, a magnet’s coercivity changes gradually as its temperature rises or falls. But the new nanomaterial shows this isn’t always true. To make the material, a team led by physicist Ivan Schuller at the University of California, San Diego, deposited an ultrathin 10-nanometer layer of nickel onto a 100-nanometer-thick wafer of a substance called vanadium oxide. The scientists then cooled the mixture and ramped up a magnetic field until the nickel’s grains started to flip. This process allowed the scientists to measure the material’s coercivity at temperatures down to negative 153°C.
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