In the crystal Rb1-xV2Te2O, the spins of vanadium atoms arrange in a checkerboard pattern: each spin is surrounded by opposite spins. This pattern is called G-type antiferromagnetism. Neutrons passing through the sample scatter off this pattern and reveal its geometry, like light from a flashlight shining through blinds casting stripes on a wall.
Earlier, photoemission and tunneling microscopy data suggested a different order — with d-wave symmetry, where spins are oriented in a more intricate way. The new result shows that the actual structure is simpler, but it doesn't fit the previous picture of altermagnetism. Altermagnets are materials where electrons with different spins move differently, even though the net magnetic moment is zero, as in antiferromagnets.
This discovery forces a rethink of how the crystal lattice and spins are coupled in this material. Possibly, the layered structure of Rb1-xV2Te2O allows several types of magnetic order, and the one seen by neutrons is just one of them. For spintronics, where information is manipulated using spins, such materials are like new pieces in a construction set: the more options, the more interesting it is to build devices.
Neutron diffraction is like X-ray diffraction, but instead of X-rays, it uses neutrons from a nuclear reactor. Neutrons are sensitive to spins, not electron clouds, so they see magnetic order directly.