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Condensed Matter Research Seminar: Allan Leishman, University of Notre Dame

Thu Oct 22, 2020 4:00PM - 5:00PM • Calendars: Condensed Matter Seminar

Measuring topological stability of magnetic skyrmions

Allan Leishman, Physics Graduate Student
University of Notre Dame

Magnetic skyrmions show promise for future data storage applications due to their small size and observation at a wide range of temperatures and magnetic fields.  Key to their surprising stability is a topological energy barrier which must be overcome to create or destroy a skyrmion in a magnetic material.  Understanding the nature of this energy barrier and how to maximize it is essential to the longstanding goal of building nanoscale skyrmion devices at room temperature and zero applied field. We have developed a novel method for measuring the topological energy barrier of skyrmion lattices (SkL) and have used it to characterize the prototypical skyrmion hosting material MnSi. Using small angle neutron scattering (SANS) we have observed a small hysteresis associated with entering and leaving the SkL phase. By modelling this hysteresis with an adapted Preisach free energy curve, we can extract the SkL energy barrier and infer information about the microscopic details of the phase transition.  Combining our SANS result  with atomistic spin simulations, we conclude  that the SkL forms progressively in domains which are hundreds of nanometers in size. In this seminar I will discuss the fundamentals of magnetic skyrmion lattices, motivate why SANS is an excellent technique to study skyrmions, and outline our recent findings in MnSi.

All interested persons are invited to attend remotely—email physics@nd.edu for information.

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