Skyrmions and Vortices in Magnetic Systems
| Date/Time: | Monday, 13 Nov 2017 from 4:10 pm to 5:00 pm |
|---|---|
| Location: | Phys 0003 |
| Phone: | 515-294-5441 |
| Channel: | College of Liberal Arts and Sciences |
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Abstract: The history of magnetism dates back to earlier than 600 B.C., but it is only in the twentieth century that scientists have begun to understand it, and develop technologies based on this understanding. The new experimental techniques that were developed over twentieth century allowed physicists to discover new forms of magnetism that they called "antiferromagnets". Unlike ferromagnets, the magnetic moments of antiferromagnets point along different directions in such a way that the magnetic unit cell has no net magnetic moment. Typical configurations of antiferromagnets are spiral orderings arising from competing exchange interactions or from the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between magnetic moments embedded in metallic environments.
The new century started with the observation of a new generation of antiferromagnets comprising more exotic magnetic textures, such as skyrmion and vortex crystals [1-3]. These textures were unveiled thanks to the enormous progress made in real and reciprocal space visualization techniques. We will discuss a few attractive properties of these novel phases and the simple principles that should guide the experimental search. For instance, we will see that an external magnetic field can induce a skyrmion crystal phase in hexagonal lattices (lattices with six equivalent orientations for the spiral ordering) with easy-axis anisotropy [4-10]. Moreover, we will see that magnetic skyrmions behave as mesoscale particles, which can order in different three-dimensional structures, such as face centered tetragonal and hexagonal closed packed crystals [10].
References
[1] U. Rößler, A. Bogdanov, and C. Pfleiderer, Nature 442, 797 (2006).
[2] A. N. Bogdanov and D. A. Yablonskii, Sov. Phys. JETP 68, 101 (1989).
[3] A. Bogdanov and A. Hubert, Journal of Magnetism and Magnetic Materials 138, 255 (1994).
[4] S. Hayami, S.-Z. Lin, and C. D. Batista, Phys. Rev. B 93, 184413 (2016).
[5] A. O. Leonov and M. Mostovoy, Nature Communications 6, 8275 (2015).
[6] Shi- Zeng Lin, Satoru Hayami and C. D. Batista, Phys. Rev. Lett. 116, 187202 (2016).
[7] C. D. Batista, S-Z. Lin, S. Hayami and Y. Kamiya, Reports on Progress in Physics, Vol 79, 8 (2016).
[9] Satoru Hayami, Shi-Zeng Lin, Yoshitomo Kamiya, and Cristian D. Batista, Phys. Rev. B 94, 174420.
[10] Shi-Zeng Lin and C. D. Batista, arXiv:1707.05818v1.
BIO: Prof. Cristian Batista received his Ph. D. from the Instituto Balseiro, Bariloche (Argentina) in 1996. In 2001, he was awarded the J. R. Oppenheimer fellowship of the Los Alamos National Laboratory. In 2004, he became a regular staff member of the T-4 group of the Los Alamos National Laboratory. He was named Fellow of the American Physical Society in 2014. Since 2016, he is the Wills Lincoln Chair Professor at the University of Tennessee (Knoxville) and has a joint position with Oak Ridge National Laboratory, where he is the deputy group leader of the Shull Wollan center.