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Wednesday, February 27

Unusual Hall Effect Anomaly from the Non-Trivial Spin Texture

Minhyea Lee, University of Colorado, Boulder
Materials Science and Technology Division Seminar
11:00 AM — 12:00 PM, Chemical and Material Sciencew Building (4100), Room J-302
Contact: Brian Sales (, 865.576.7646


Recent works in B20 type transition metal compounds have revealed a new topological object in spin systems--the skyrmion, a particle-like object in which spins point all directions to wrap around the sphere. While neutron scattering and scanning probe experiments confirmed the existence of individual skyrmions and skyrmion lattices in a particular part of the phase diagram, the interaction between skyrmions and electronic degrees of freedom remains to be unveiled. In this talk, we report the observation of a highly unusual Hall current in the helical magnet MnSi under pressure. In addition to the normal Hall effect and the anomalous part that arises from spontaneous magnetization, the Hall conductivity displays a distinctive stepwise field profile quite unlike any other Hall response observed in solids. Under pressure, this additional contribution was observed in a much larger range of temperature than the so-called A-phase, where the skyrmion lattice was observed in ambient pressure. I will also present our recent results of the Hall effect in Fe doped MnSi compared with the pressure data and discuss the implications for the magnetic phase diagram.