Physics Spotlight  
A domain wall (gray panel at center) separates regions with different spin orientations (green and blue arrows). MIT researchers discovered that a magnetic field applied at one particular angle through a single crystal of a new magnetic quantum material makes it harder for electrons to cross this domain wall. A domain wall (gray panel at center) separates regions with different spin orientations (green and blue arrows). MIT researchers discovered that a magnetic field applied at one particular angle through a single crystal of a new magnetic quantum material makes it harder for electrons to cross this domain wall. Illustration: Leon Balents

Approaching the magnetic singularity

MIT researchers discover a material that changes electrical resistance only when a magnetic field is applied at a narrowly confined angle.

Materials Research Laboratory
June 20, 2019

In many materials, electrical resistance and voltage change in the presence of a magnetic field, usually varying smoothly as the magnetic field rotates. This simple magnetic response underlies many applications including contactless current sensing, motion sensing, and data storage. In a crystal, the way that the charge and spin of its electrons align and interact underlies these effects. Utilizing the nature of the alignment, called symmetry, is a key ingredient in designing a functional material for electronics and the emerging field of spin-based electronics (spintronics).  

Recently a team of researchers from MIT, the French National Center for Scientific Research (CNRS) and École Normale Supérieure (ENS) de Lyon, University of California at Santa Barbara (UCSB), the Hong Kong University of Science and Technology (HKUST), and NIST Center for Neutron Research, led by Joseph G. Checkelsky, assistant professor of physics at MIT, has discovered a new type of magnetically driven electrical response in a crystal composed of cerium, aluminum, germanium, and silicon. 

At temperatures below 5.6 kelvins (corresponding to -449.6 degrees Fahrenheit), these crystals show a sharp enhancement of electrical resistivity when the magnetic field is precisely aligned within an angle of 1 degree along the high symmetry direction of the crystal. This effect, which the researchers have named “singular angular magnetoresistance,” can be attributed to the symmetry — in particular, the ordering of the cerium atoms’ magnetic moments. Their results are published today in the journal Science.

Physics in the News icon