192nd Special MMU seminar


Giant topological Hall effect in strained Fe0.7Co0.3Si epilayers

Prof. C. H. Marrows
1School of Physics & Astronomy, University of Leeds, Leeds, U.K.
email: c.h.marrows@leeds.ac.uk

N. A. Porter1, P. Sinha1, M. B. Ward2, A. N. Dobrynin3, R. M. D. Brydson2,
T. Charlton4, C. J. Kinane4, M. D. Robertson5, S. Langridge4
2SPEME, Faculty of Engineering, University of Leeds, Leeds, U.K., 3Diamond Light Source, Didcot, U.K.,
4ISIS, Rutherford Appleton Laboratory, Didcot, U.K., 5Department of Physics, Acadia University, Wolfville, Nova Scotia, Canada
Date: Jan. 23 (Thu), 2014
Time: 10:30 - 12:00
Place: 8F medium seminar room, Sengen
The coupling of electron spin to real-space magnetic textures leads to a variety of interesting magnetotransport effects. The chiral spin textures, such as skyrmion lattices, found in B20-lattice magnets [1,2] give rise, via real-space Berry phases and associated emergent magnetic fields, to the topological Hall effect [3], but it is typically rather small. Here we show that B20-ordered Fe0.7Co0.3Si epilayers grown on Si (111) substrates display a giant topological Hall effect due to the combination of three favourable properties: they have a high spin-polarisation, a large ordinary Hall coefficient, and a large emergent magnetic field. Moreover they show enhanced ordering temperatures due to the presence of epitaxial strain [4]. The topological Hall resistivity is as large as ~750 nĦcm at helium temperatures, an order of magnitude larger than in MnSi [5] and roughly four times that found in MnGe [6]. Furthermore, we observed a drop in the longitudinal resistivity of ~100 nĦcm at low temperatures in the same field range, suggesting it is of topological origin [7]. That such strong effects can be found in material grown in thin film form on commercial silicon wafer bodes well for skyrmion-based spintronics [8].
We would like to acknowledge funding from EPSRC and the FP7 ITN Q-NET.

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[4] P. Sinha, N. A. Porter, & C. H. Marrows, Strain-induced effects on the magnetic and electronic properties of epitaxial FeCoSi thin films. arXiv:1307.7301 [condmat.mtrl-sci] (2013).
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