A new topological magnet with colossal angular magnetoresistance

One key challenge in spintronics is finding an efficient and sensitive way to electrically detect the electronic spin state. For example, the discovery of giant magnetoresistance (GMR) in the late 1980s, allowed for such functionality. In GMR, a large change in electrical resistance occurs under the magnetic field depending on parallel or antiparallel spin configurations of the ferromagnetic bilayer. The discovery of GMR has led to the development of hard-disk drive technology, which is technically the first-ever mass-produced spintronic device. Since then, discoveries of other related phenomena, including colossal magnetoresistance (CMR) which occurs in the presence of a magnetic field, have advanced our understanding of the interplay between spin and charge degrees of freedom and served as a foundation of emergent spintronic applications.

In the latest issue of the journal Nature , a research team led by Prof. Kim Jun Sung in Center for Artificial Low Dimensional Electron Systems within the Institute for Basic Science (IBS, South Korea) and Physics Department at Pohang University of Science and Technology (POSTECH, South Korea) found a new magnetotransport phenomenon, in the magnetic semiconductor Mn 3 Si 2 Te 6 . The group found that the magnitude of change in resistance can reach as large as a billion-fold under a rotating magnetic field. This unprecedented shift of resistance depending on magnetic field angle is called colossal angular magnetoresistance (CAMR).

Schematic illustration of the metal-insulator transition in magnetic topological semiconductors. The topological nodal line is where electronic bands cross and form a line in energy-momentum space. With magnetic ordering, spin-orbit energy depending on the spin direction decides whether the system is a semiconductor (left) or metal (right). Credit: Institute for Basic Science Read more

Crystal structure of topological magnet Mn3Si2Te6 (upper left). It has a unique structure where Mn atoms (red) are intercalated between Te atom (grey) layers. Mn atoms in basic and intercalated structures are labeled as Mn1 (upper right) and Mn2 (lower right) layers, respectively. Each layer has a different spin moment and direction, which results in ferrimagnetic ordering. An optical image of Mn3Si2Te6 is shown in the lower left panel. Credit: Institute for Basic Science Read more

Colossal angular magnetoresistance in Mn3Si2Te6 single crystal. As shown in the inset, when electrical resistivity is measured in a rotating magnetic field, a huge variation of resistivity about a billion times is observed. Credit: Institute for Basic Science Read more