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Thursday, May 19, 2016
11:00 AM - 1:00 PM
CNLS Conference Room (TA-3, Bldg 1690)

Seminar

Curvature–induced effects in low-dimensional nanomagnets

Denis D. Sheka
Taras Shevchenko National University of Kyiv, Ukraine

Curvature-driven modification of physical properties of magnetic systems with nontrivial geometry is the subject of intensive research. One can distinguish two groups of curvatureinduced effects in nanomagnets: (i) magnetochiral effects unite the phenomena of curvatureinduced chiral symmetry breaking and (ii) topologically induced magnetization patterning appears in curvilinear magnets, where orientation of the effective anisotropy axis is determined by the geometry. We develop a general fully 3D approach to study dynamical and static properties of arbitrary curved ferromagnet nanowires and nanoshells [1, 2]. According to this approach two additional interaction terms appear in the exchange energy functional due to the curvature and torsion in wires (Gaussian and mean curvatures in the case of shells): an effective Dzyaloshinskii– Moriya (DMI) interaction term and a geometrically induced anisotropy term. The magnetochiral effects are originated from the effective DMI while the magnetization patterning is related to the effective anisotropy. Using such an approach we predict the coupling between the geometrical chirality of the system with magnetochirality of magnetization structure [3, 4], and a series of new effects such as torsion induced modification of the ground state magnetization [2], the DMI caused splitting in the spin-wave spectrum [3], the domain wall pinning [5]. The curvature and torsion effects can be efficiently used to control domain walls in curved nanowires by spin currents [6, 7]. [1] Y. Gaididei, V. P. Kravchuk, and D. D. Sheka, Phys. Rev. Lett. 112, 257203 (2014). [2] D. D. Sheka, V. P. Kravchuk, and Y. Gaididei, Journal of Physics A: Mathematical and Theoretical 48, 125202 (2015). [3] D. D. Sheka, V. P. Kravchuk, K. V. Yershov, and Y. Gaididei, Phys. Rev. B 92, 054417 (2015). [4] O. V. Pylypovskyi, V. P. Kravchuk, D. D. Sheka, D. Makarov, O. G. Schmidt, and Y. Gaididei, Phys. Rev. Lett. 114, 197204 (2015). [5] K. V. Yershov, V. P. Kravchuk, D. D. Sheka, and Y. Gaididei, Phys. Rev. B 92, 104412 (2015). [6] O. V. Pylypovskyi, D. D. Sheka, V. P. Kravchuk, K. V. Yershov, D. Makarov, and Y. Gaididei, Scienti c Reports 6, 23316 (2016). [7] K. V. Yershov, V. P. Kravchuk, D. D. Sheka, and Y. Gaididei, Phys. Rev. B 93, 094418 (2016).

Host: Avadh Saxena