Magnets, by definition, produce magnetic fields, right? Not necessarily, says a team of Japanese physicists in the September 17th issue of Physical Review Letters. Hiromichi Adachi of KEK, the High Energy Accelerator Research Organization in Tsukuba, Japan, and colleagues created a magnetic alloy that under certain conditions lacks magnetism.
In ordinary magnets, both individual electron spins and the motion of electrons in their atomic orbitals generate magnetic fields. Combined, these fields produce the material's total magnetic field. In some rare-earth elements, though, the two contributions are nearly identical. With that in mind, Adachi's group created an alloy from aluminum and samarium, a rare-earth element having opposite spin and orbital moments that vary with temperature.
They found that at temperatures just above and below 70 degrees Kelvin, they could readily magnetize the SmAl2 alloy using an external magnetic field. But at precisely 70 degrees Kelvin, the spin and orbital moments in the material canceled each other out. The alloy won't find uses on refrigerators or as compass needles, but the scientists suggest it may have applications in spintronicsa new class of electronic devices that harness electron spins instead of charge.