Research challenge 3: Thin Films, modelling and devices

Research challenge 3: Thin Films, modelling and devices

How do we transfer the desired properties of bulk crystals to application-enabling thin films?

Our thin film growth provides insights into the materials challenges currently holding back this field. Currently skyrmions can only be observed in bulk single crystals, and bulk samples that have been thinned down for electron microscopy. Successful attempts to grow high-quality, phase-pure thin films have not resulted in the unambiguous observation of skyrmions. As is known from B20 thin film systems, strain is a critical, presumably detrimental, parameter for the formation of a skyrmion phase. However, strain is also the key to enhance the magnetic transition temperature.

Our study of the strain state of epitaxial MnSi films on Si(111) substrates in the thick film limit (100–500 Å) as a function of film thickness using polarization-dependent extended x-ray absorption fine structure (EXAFS) [2-2016].

How can we efficiently and reliably generate skyrmions?

A skyrmion-based data storage device must contain an efficient and reliable writing module, based on well-controlled and localised skyrmion creation. This can be achieved using either the localised application of a spin-polarised current or an external magnetic field. We will determine the optimal design of a skyrmion generator and determine the circumstances under which the skyrmions are created. We will determine how the essential writing parameters (speed, reliability, energy efficiency) depend on different designs and parameters of skyrmion generators. We will avoid the use of mechanical parts that are still present in conventional hard disk drives, and which are the main limiting factor in terms of robustness, speed and cost.


Skyrmion-based devices have been proposed as a promising solution for low-energy data storage. These devices include racetrack or logic structures and require skyrmions to be confined in regions with dimensions comparable to the size of a single skyrmion. Here we examine skyrmions in FeGe device shapes using Lorentz transmission electron microscopy to reveal the consequences of skyrmion confinement in a device-like structure [14 - 2022].

How do we develop skyrmion transport devices?

We have worked to understand how an array of skyrmions can be moved along a nanostructure that forms the core of a shift-register-like system. The crucial parameter is the optimal current density required to drive a train of skyrmions. Since a single information bit is encoded by the skyrmion's presence/absence, we must study whether this skyrmion chain can be moved uniformly, without changing their relative distances.

How do we develop skyrmion detectors?

After exciting and transporting skyrmions, a means of detection needs to be developed. Magnetic spin-valve and tunnel structures have been studied, as well other schemes, before a recommendation will be given for the fabrication of the structures. A straightforward approach is to use the topological Hall effect (THE). Generally, however, the expected THE voltage is rather small, making it necessary to enhance the signal.

We have developed reciprocal space techniques to determine the skyrmion Hall angle in the skyrmion lattice state of FeGe [2 - 2021].

Materials synthesis has been carried out via molecular beam epitaxy (MBE) and UHV magnetron sputtering. Hitherto we have successfully grown the B20 materials MnSi, FeGe, and MnGe in thin film form.

For this project, we have four thin film growth systems at our disposal, covering the materials classes from intermetallics, to oxides, chalcogenides, and silicides. Two state-of-the-art MBE systems are located on the Rutherford-Appleton Laboratory site in Harwell, dedicated for oxides and chalcogenides. A third MBE, for intermetallics and silicides, as well as a UHV magnetron sputterer, are located in the Clarendon Laboratory at Oxford, and have been successfully used for the growth of B20 thin films.


We have grown skyrmion hosting materials in the form of thin films and of nanostructures using molecular beam epitaxy (MBE), UHV sputtering, and chemical vapor deposition; their structural, magnetic, and electrical characterization; as well as exploratory device studies.

Experimental methodology

Thin films are patterned into nanodevices in Oxford's nanofabrication cleanrooms. Photolithography e-beam lithography, and focused ion beam are employed for fabricating a variety of structures that are then optimised for their respective purpose: in-plane contact structures, Hall bars for magnetotransport studies, spin valves, and magnetic tunnel junction-like structures for skyrmion excitation and detection.


We have created a chiral bobber structure via heterostructure engineering. (a) Illustration of the heterostructure by contacting two different skyrmion species with comparable lateral dimensions. (b) Simulation results of the skyrmion tube structure at field between BA1 and BA2. (c) z component of the dipolar field distribution from a skyrmion in the multilayer. (d) Calculated chiral bobber structure formed in Cu2OSeO3 at a field between the first and second upper critical fields BA2 and BA3, respectively [16 - 2021].

We have investigated the magnetic states in these films by magnetometry, neutron diffraction, ferromagnetic resonance and muon-spin spectroscopy. We have also used many advanced techniques such as LTEM, resonant elastic X-ray scattering including CD-REXS, small angle neutron scattering, and X-ray holography to image the skyrmion lattice and other magnetic textures, in both 2D and 3D.


We have studied the full 3D spin order in the skyrmion lattice of Cu2OSeO3 by means polarized REXS as a depth-dependent probe. Here we illustrate the skyrmion order ranging from Néel- to Bloch-twisting with increasing depth below a surface. (A1–A4) Hedgehog spin configuration on the surface of a sphere for skyrmions with winding number N=1 varying between pure Néel-twisting (A1) and pure Bloch-twisting (A4). (B1–B4) Real-space planar spin configuration varying between pure Néel-twisting (B1) and pure Bloch-twisting (B4). A stereographic projection connects the planar patterns shown in B1–B4 with the hedgehog configurations shown in A1–A4, respectively. (C1–C4) Calculated dichroic REXS diffraction pattern associated with a hexagonal lattice composed of the spin configurations shown in B1–B4. The orientation of the extinction line marked by a white arrow corresponds to the helicity angle χ denoted on the right-hand side of the panels. Consequently, the chirality of the skyrmions can be straightforwardly determined (see SI Appendix, Supplementary Materials). (C1) χ=180 and (C4) χ=90 correspond to pure Néel- and pure Bloch-twisting, respectively. (D) Schematic illustration of the change from Néel- to Bloch-twisting with increasing depth below the surface. The colour coding reflects the z direction of the magnetization [9 -2018].

Micromagnetic simulations have been used in order to determine the optimal implementation method for the development of novel high-density, low-power skyrmion-based data storage and processing devices. The use of skyrmions in thin film devices requires them to be stable in zero external magnetic field. We have worked to refine the finite-difference and finite-element simulation tools to cover thin films and finite dimensions, at T=0 K and at finite temperatures. Design of the skyrmion-based data storage device requires the multidisciplinary approach including micromagnetic modeling, numerical analysis, complexity, software development, and more. The simulation tools have already been fully developed at the University of Southampton. We have made use of the University's High Performance Computing Facilities, which has allowed us to perform simulations by varying different parameters over a very wide range.



Publications

Please find below a list of papers published by the UK Skyrmion Project team as a results of work carried out during the course of the project under Research Challenges, 1, 2, and 3.

Some of the early papers are the result of pilot studies carried out my members of the UKSP team before the project was funded by the EPSRC.

Details of every publication, including an abstract and link to the paper in the journal can be found on the Journal section of this website under the heading Science.



Publications 2016


[1 - 2016] R. Carey, M. Beg, M. Albert, M.-A. Bisotti, D. Cortés-Ortuño, M. Vousden, W. Wang, O. Hovorka, H. Fangohr, Hysteresis of nanocylinders with Dzyaloshinskii-Moriya interaction, Applied Physics Letters 109, 122401 (2016).


[2 - 2016] A. I. Figueroa, S. L. Zhang, A. A. Baker, R. Chalasani, A. Kohn, S. C. Speller, D. Gianolio, C. Pfleiderer, G. van der Laan, T. Hesjedal, Strain in epitaxial MnSi films on Si(111) in the thick film limit studied by polarization-dependent extended x-ray absorption fine structure, Physical Review B 94, 174107 (2016).


[3 - 2016] V. P. Kravchuk, U. K. Rößler, O. M. Volkov, D. D. Sheka, J. van den Brink, D. Makarov, H. Fuchs, H. Fangohr, Y. Gaididei, Topologically stable magnetization states on a spherical shell: Curvature-stabilized skyrmions, Physical Review B 94, 144402 (2016).


[4 - 2016] T. Lancaster, R. C. Williams, I. O. Thomas, F. Xiao, F. L. Pratt, S. J. Blundell, J. C. Loudon, T. Hesjedal, S. J. Clark, P. D. Hatton, M. Ciomaga Hatnean, D. S. Keeble, G. Balakrishnan, Transverse field muon-spin rotation signature of the skyrmion-lattice phase in Cu2OSeO3, Physical Review B 91, 224408 (2015).


[5 - 2016] T. Lancaster, F. Xiao, Z. Salman, I. O. Thomas, S. J. Blundell, F. L. Pratt, S. J. Clark, T. Prokscha, A. Suter, S. L. Zhang, A. A. Baker, T. Hesjedal, Transverse field muon-spin rotation measurement of the topological anomaly in a thin film of MnSi, Physical Review B 93, 140412 (2016).


[6 - 2016] A. O. Leonov, J. C. Loudon, A. N. Bogdanov, Spintronics via non-axisymmetric chiral skyrmions, Applied Physics Letters 109, 172404 (2016).


[7 - 2016] A. O. Leonov, T. L. Monchesky, J. C. Loudon, A. N. Bogdanov, Three-dimensional chiral skyrmions with attractive interparticle interactions, Journal of Physics: Condensed Matter 28, 35LT01 (2016).


[8 - 2016] S. L. Zhang, A. Bauer, H. Berger, C. Pfleiderer, G. v. d. Laan, T. Hesjedal, Imaging and manipulation of skyrmion lattice domains in Cu2OSeO3, Applied Physics Letters 109, 192406 (2016).


[9 - 2016] S. L. Zhang, T. Hesjedal, The magneto-Hall difference and the planar extraordinary Hall balance, Aip Advances 6, 045019 (2016).




Publications 2017


[1 - 2017] A. Baker, M. Beg, G. Ashton, M. Albert, D. Chernyshenko, W. Wang, S. Zhang, M.-A. Bisotti, M. Franchin, C. L. Hu, R. Stamps, T. Hesjedal, H. Fangohr, Proposal of a micromagnetic standard problem for ferromagnetic resonance simulations, Journal of Magnetism and Magnetic Materials 421, 428-439 (2017).


[2 - 2017] M. Beg, M. Albert, M.-A. Bisotti, D. Cortés-Ortuño, W. Wang, R. Carey, M. Vousden, O. Hovorka, C. Ciccarelli, C. S. Spencer, C. H. Marrows, H. Fangohr, Dynamics of skyrmionic states in confined helimagnetic nanostructures, Physical Review B 95, 014433 (2017).


[3 - 2017] D. Cortés-Ortuño, W. Wang, M. Beg, R. A. Pepper, M.-A. Bisotti, R. Carey, M. Vousden, T. Kluyver, O. Hovorka, H. Fangohr, Thermal stability and topological protection of skyrmions in nanotracks, Scientific Reports 7, 4060 (2017).


[4 - 2017] S. L. Zhang, I. Stasinopoulos, T. Lancaster, F. Xiao, A. Bauer, F. Rucker, A. A. Baker, A. I. Figueroa, Z. Salman, F. L. Pratt, S. J. Blundell, T. Prokscha, A. Suter, J. Waizner, M. Garst, D. Grundler, G. van der Laan, C. Pfleiderer, T. Hesjedal, Room-temperature helimagnetism in FeGe thin films, Scientific Reports 7, 123 (2017).


[5 - 2017] S. L. Zhang, G. van der Laan, T. Hesjedal, Direct experimental determination of the topological winding number of skyrmions in Cu2OSeO3, Nature Communications 8, 14619 (2017).


[6 - 2017] S. L. Zhang, G. van der Laan, T. Hesjedal, Direct experimental determination of spiral spin structures via the dichroism extinction effect in resonant elastic soft x-ray scattering, Physical Review B 96, 094401 (2017).




Publications 2018


[1 - 2018] D. Cortés-Ortuño, M. Beg, V. Nehruji, L. Breth, R. Pepper, T. Kluyver, G. Downing, T. Hesjedal, P. Hatton, T. Lancaster, R. Hertel, O. Hovorka, H. Fangohr, Proposal for a micromagnetic standard problem for materials with Dzyaloshinskii–Moriya interaction, New Journal of Physics 20, 113015 (2018).


[2 - 2018] K. J. A. Franke, B. M. Huddart, T. J. Hicken, F. Xiao, S. J. Blundell, F. L. Pratt, M. Crisanti, J. A. T. Barker, S. J. Clark, A. Štefančič, M. C. Hatnean, G. Balakrishnan, T. Lancaster, Magnetic phases of skyrmion-hosting GaV4S8-ySey (y=0,2,4,8) probed with muon spectroscopy, Physical Review B 98, 054428 (2018).


[3 - 2018] W. Jiang, J. Xia, X. Zhang, Y. Song, C. Ma, H. Fangohr, G. Zhao, X. Liu, W. Zhao, Y. Zhou, Dynamics of Magnetic Skyrmion Clusters Driven by Spin-Polarized Current With a Spatially Varied Polarization, IEEE Magnetics Letters 9, 1-5 (2018).


[4 - 2018] J. C. Loudon, A. O. Leonov, A. N. Bogdanov, M. C. Hatnean, G. Balakrishnan, Direct observation of attractive skyrmions and skyrmion clusters in the cubic helimagnet Cu2OSeO3, Physical Review B 97, 134403 (2018).


[5 - 2018] R. A. Pepper, M. Beg, D. Cortés-Ortuño, T. Kluyver, M.-A. Bisotti, R. Carey, M. Vousden, M. Albert, W. Wang, O. Hovorka, H. Fangohr, Skyrmion states in thin confined polygonal nanostructures, Journal of Applied Physics 123, 093903 (2018).


[6 - 2018] T. Shang, M. Smidman, S. K. Ghosh, C. Baines, L. J. Chang, D. J. Gawryluk, J. A. T. Barker, R. P. Singh, D. M. Paul, G. Balakrishnan, E. Pomjakushina, M. Shi, M. Medarde, A. D. Hillier, H. Q. Yuan, J. Quintanilla, J. Mesot, T. Shiroka, Time-Reversal Symmetry Breaking in Re-Based Superconductors, Physical Review Letters 121, 257002 (2018).


[7 - 2018] A. Štefančič, S. H. Moody, T. J. Hicken, M. T. Birch, G. Balakrishnan, S. A. Barnett, M. Crisanti, J. S. O. Evans, S. J. R. Holt, K. J. A. Franke, P. D. Hatton, B. M. Huddart, M. R. Lees, F. L. Pratt, C. C. Tang, M. N. Wilson, F. Xiao, T. Lancaster, Origin of skyrmion lattice phase splitting in Zn-substituted Cu2OSeO3, Physical Review Materials 2, 111402 (2018).


[8 - 2018] S. Zhang, F. Kronast, G. van der Laan, T. Hesjedal, Real-Space Observation of Skyrmionium in a Ferromagnet-Magnetic Topological Insulator Heterostructure, Nano Letters 18, 1057-1063 (2018).


[9 - 2018] S. Zhang, G. van der Laan, J. Müller, L. Heinen, M. Garst, A. Bauer, H. Berger, C. Pfleiderer, T. Hesjedal, Reciprocal space tomography of 3D skyrmion lattice order in a chiral magnet, Proceedings of the National Academy of Sciences 115, 6386-6391 (2018).


[10 - 2018] S. L. Zhang, G. van der Laan, W. W. Wang, A. A. Haghighirad, T. Hesjedal, Direct Observation of Twisted Surface skyrmions in Bulk Crystals, Physical Review Letters 120, 227202 (2018).


[11 - 2018] S. L. Zhang, W. W. Wang, D. M. Burn, H. Peng, H. Berger, A. Bauer, C. Pfleiderer, G. van der Laan, T. Hesjedal, Manipulation of skyrmion motion by magnetic field gradients, Nature Communications 9, 2115 (2018).




Publications 2019


[1 - 2019] M. T. Birch, R. Takagi, S. Seki, M. N. Wilson, F. Kagawa, A. Štefančič, G. Balakrishnan, R. Fan, P. Steadman, C. J. Ottley, M. Crisanti, R. Cubitt, T. Lancaster, Y. Tokura, P. D. Hatton, Increased lifetime of metastable skyrmions by controlled doping, Physical Review B 100, 014425 (2019).


[2 - 2019] R. Brearton, M. W. Olszewski, S. Zhang, M. R. Eskildsen, C. Reichhardt, C. J. O. Reichhardt, G. van der Laan, T. Hesjedal, Skyrmions in anisotropic magnetic fields: strain and defect driven dynamics, MRS Advances 4, 643-650 (2019).


[3 - 2019] D. M. Burn, S. L. Zhang, S. Wang, H. F. Du, G. van der Laan, T. Hesjedal, Helical magnetic ordering in thin FeGe membranes, Physical Review B 100, 184403 (2019).


[4 - 2019] D. Cortés-Ortuño, N. Romming, M. Beg, K. von Bergmann, A. Kubetzka, O. Hovorka, H. Fangohr, R. Wiesendanger, Nanoscale magnetic skyrmions and target states in confined geometries, Physical Review B 99, 214408 (2019).


[5 - 2019] K. J. A. Franke, P. R. Dean, M. C. Hatnean, M. T. Birch, D. D. Khalyavin, P. Manuel, T. Lancaster, G. Balakrishnan, P. D. Hatton, Investigating the magnetic ground state of the skyrmion host material Cu2OSeO3 using long-wavelength neutron diffraction, AIP Advances 9, 125228 (2019).


[6 - 2019] R. A. Gallardo, D. Cortés-Ortuño, T. Schneider, A. Roldán-Molina, F. Ma, R. E. Troncoso, K. Lenz, H. Fangohr, J. Lindner, P. Landeros, Flat Bands, Indirect Gaps, and Unconventional Spin-Wave Behavior Induced by a Periodic Dzyaloshinskii-Moriya Interaction, Physical Review Letters 122, 067204 (2019).


[7 - 2019] B. M. Huddart, M. T. Birch, F. L. Pratt, S. J. Blundell, D. G. Porter, S. J. Clark, W. Wu, S. R. Julian, P. D. Hatton, T. Lancaster, Local magnetism, magnetic order and spin freezing in the ‘nonmetallic metal’ FeCrAs, Journal of Physics: Condensed Matter 31, 285803 (2019).


[8 - 2019] T. Lancaster, Skyrmions in magnetic materials, Contemporary Physics 60, 246-261 (2019).


[9 - 2019] W. Li, I. Bykova, S. Zhang, G. Yu, R. Tomasello, M. Carpentieri, Y. Liu, Y. Guang, J. Gräfe, M. Weigand, D. M. Burn, G. van der Laan, T. Hesjedal, Z. Yan, J. Feng, C. Wan, J. Wei, X. Wang, X. Zhang, H. Xu, C. Guo, H. Wei, G. Finocchio, X. Han, G. Schütz, Anatomy of Skyrmionic Textures in Magnetic Multilayers, Advanced Materials 31, 1807683 (2019).


[10 - 2019] X. Li, S. Zhang, H. Li, D. A. Venero, J. S. White, R. Cubitt, Q. Huang, J. Chen, L. He, G. van der Laan, W. Wang, T. Hesjedal, F. Wang, Oriented 3D Magnetic Biskyrmions in MnNiGa Bulk Crystals, Advanced Materials 31, 1900264 (2019).


[11 - 2019] J. Liu, T. Hesjedal, Magnetic Topological Insulator Heterostructures: A Review, Advanced Materials n/a, 2102427


[12 - 2019] J. C. Loudon, A. C. Twitchett-Harrison, D. Cortés-Ortuño, M. T. Birch, L. A. Turnbull, A. Štefančič, F. Y. Ogrin, E. O. Burgos-Parra, N. Bukin, A. Laurenson, H. Popescu, M. Beg, O. Hovorka, H. Fangohr, P. A. Midgley, G. Balakrishnan, P. D. Hatton, Do Images of Biskyrmions Show Type-II Bubbles?, Advanced Materials 31, 1806598 (2019).


[13 - 2019] M. N. Wilson, M. Crisanti, C. Barker, A. Štefančič, J. S. White, M. T. Birch, G. Balakrishnan, R. Cubitt, P. D. Hatton, Measuring the formation energy barrier of skyrmions in zinc-substituted Cu2OSeO3, Physical Review B 99, 174421 (2019).


[14 - 2019] S. Zhang, T. Hesjedal, G. van der Laan, Skyrmions getting an X-ray, MagNews 2019, 22-22 (2020).




Publications 2020


[1 - 2020] M. T. Birch, D. Cortés-Ortuño, L. A. Turnbull, M. N. Wilson, F. Groß, N. Träger, A. Laurenson, N. Bukin, S. H. Moody, M. Weigand, G. Schütz, H. Popescu, R. Fan, P. Steadman, J. A. T. Verezhak, G. Balakrishnan, J. C. Loudon, A. C. Twitchett-Harrison, O. Hovorka, H. Fangohr, F. Y. Ogrin, J. Gräfe, P. D. Hatton, Real-space imaging of confined magnetic skyrmion tubes, Nature Communications 11, 1726 (2020).


[2 - 2020] M. T. Birch, S. H. Moody, M. N. Wilson, M. Crisanti, O. Bewley, A. Štefančič, G. Balakrishnan, R. Fan, P. Steadman, D. Alba Venero, R. Cubitt, P. D. Hatton, Anisotropy-induced depinning in the Zn-substituted skyrmion host Cu2OSeO3, Physical Review B 102, 104424 (2020).


[3 - 2020] R. Brearton, G. van der Laan, T. Hesjedal, Magnetic skyrmion interactions in the micromagnetic framework, Physical Review B 101, 134422 (2020).


[4 - 2020] D. M. Burn, S. Wang, W. Wang, G. van der Laan, S. Zhang, H. Du, T. Hesjedal, Field and temperature dependence of the skyrmion lattice phase in chiral magnet membranes, Physical Review B 101, 014446 (2020).


[5 - 2020] D. M. Burn, S. Zhang, K. Zhai, Y. Chai, Y. Sun, G. van der Laan, T. Hesjedal, Mode-Resolved Detection of Magnetization Dynamics Using X-ray Diffractive Ferromagnetic Resonance, Nano Letters 20, 345-352 (2020).


[6 - 2020] D. M. Burn, S. L. Zhang, G. Q. Yu, Y. Guang, H. J. Chen, X. P. Qiu, G. van der Laan, T. Hesjedal, Depth-Resolved Magnetization Dynamics Revealed by X-Ray Reflectometry Ferromagnetic Resonance, Physical Review Letters 125, 137201 (2020).


[7 - 2020] P. Chen, Y. Zhang, Q. Yao, F. Tian, L. Li, Z. Qi, X. Liu, L. Liao, C. Song, J. Wang, J. Xia, G. Li, D. M. Burn, G. van der Laan, T. Hesjedal, S. Zhang, X. Kou, Tailoring the Hybrid Anomalous Hall Response in Engineered Magnetic Topological Insulator Heterostructures, Nano Letters 20, 1731-1737 (2020).


[8 - 2020] M. Crisanti, M. T. Birch, M. N. Wilson, S. H. Moody, A. Štefančič, B. M. Huddart, S. Cabeza, G. Balakrishnan, P. D. Hatton, R. Cubitt, Position-dependent stability and lifetime of the skyrmion state in nickel-substituted Cu2OSeO3, Physical Review B 102, 224407 (2020).


[9 - 2020] M. Crisanti, N. Reynolds, I. Živković, A. Magrez, H. M. Rønnow, R. Cubitt, J. S. White, In situ control of the helical and skyrmion phases in Cu2OSeO3 using high-pressure helium gas up to 5 kbar, Physical Review B 101, 214435 (2020).


[10 - 2020] Y. Guang, Y. Peng, Z. Yan, Y. Liu, J. Zhang, X. Zeng, S. Zhang, S. Zhang, D. M. Burn, N. Jaouen, J. Wei, H. Xu, J. Feng, C. Fang, G. van der Laan, T. Hesjedal, B. Cui, X. Zhang, G. Yu, X. Han, Electron Beam Lithography of Magnetic Skyrmions, Advanced Materials 32, 2003003 (2020).


[11 - 2020] T. J. Hicken, S. J. R. Holt, K. J. A. Franke, Z. Hawkhead, A. Štefančič, M. N. Wilson, M. Gomilšek, B. M. Huddart, S. J. Clark, M. R. Lees, F. L. Pratt, S. J. Blundell, G. Balakrishnan, T. Lancaster, Magnetism and Néel skyrmion dynamics in GaV4S8-ySey, Physical Review Research 2, 032001 (2020).


[12 - 2020] S. J. R. Holt, A. Štefančič, C. Ritter, A. E. Hall, M. R. Lees, G. Balakrishnan, Structure and magnetism of the skyrmion hosting family GaV4S8-ySey with low levels of substitutions between 0 < y < 0.5 and 7.5 < y < 8, Physical Review Materials 4, 114413 (2020).


[13 - 2020] G. R. Lewis, J. C. Loudon, R. Tovey, Y.-H. Chen, A. P. Roberts, R. J. Harrison, P. A. Midgley, E. Ringe, Magnetic Vortex States in Toroidal Iron Oxide Nanoparticles: Combining Micromagnetics with Tomography, Nano Letters 20, 7405-7412 (2020).


[14 - 2020] J. Liu, A. Singh, B. Kuerbanjiang, C. H. W. Barnes, T. Hesjedal, Kerr effect anomaly in magnetic topological insulator superlattices, Nanotechnology 31, 434001 (2020).


[15 - 2020] J. Liu, A. Singh, Y. Y. F. Liu, A. Ionescu, B. Kuerbanjiang, C. H. W. Barnes, T. Hesjedal, Exchange Bias in Magnetic Topological Insulator Superlattices, Nano Letters 20, 5315-5322 (2020).


[16 - 2020] T. Moorsom, S. Alghamdi, S. Stansill, E. Poli, G. Teobaldi, M. Beg, H. Fangohr, M. Rogers, Z. Aslam, M. Ali, B. J. Hickey, O. Cespedes, pi-anisotropy: A nanocarbon route to hard magnetism, Physical Review B 101, 060408 (2020).


[17 - 2020] A. Štefančič, S. J. R. Holt, M. R. Lees, C. Ritter, M. J. Gutmann, T. Lancaster, G. Balakrishnan, Establishing magneto-structural relationships in the solid solutions of the skyrmion hosting family of materials: GaV4S8−ySey, Scientific Reports 10, 9813 (2020).


[18 - 2020] M. N. Wilson, M. T. Birch, A. Štefančič, A. C. Twitchett-Harrison, G. Balakrishnan, T. J. Hicken, R. Fan, P. Steadman, P. D. Hatton, Stability and metastability of skyrmions in thin lamellae of Cu2OSeO3, Physical Review Research 2, 013096 (2020).


[19 - 2020] K. Zeissler, S. Finizio, C. Barton, A. J. Huxtable, J. Massey, J. Raabe, A. V. Sadovnikov, S. A. Nikitov, R. Brearton, T. Hesjedal, G. van der Laan, M. C. Rosamond, E. H. Linfield, G. Burnell, C. H. Marrows, Diameter-independent skyrmion Hall angle observed in chiral magnetic multilayers, Nature Communications 11, 428 (2020).


[20 - 2020] S. Zhang, D. M. Burn, N. Jaouen, J.-Y. Chauleau, A. A. Haghighirad, Y. Liu, W. Wang, G. van der Laan, T. Hesjedal, Robust Perpendicular Skyrmions and Their Surface Confinement, Nano Letters 20, 1428-1432 (2020).




Publications 2021


[1 - 2021] M. T. Birch, D. Cortés-Ortuño, N. D. Khanh, S. Seki, A. Štefančič, G. Balakrishnan, Y. Tokura, P. D. Hatton, Topological defect-mediated skyrmion annihilation in three dimensions, Communications Physics 4, 175 (2021).


[2 - 2021] R. Brearton, L. A. Turnbull, J. A. T. Verezhak, G. Balakrishnan, P. D. Hatton, G. van der Laan, T. Hesjedal, Deriving the skyrmion Hall angle from skyrmion lattice dynamics, Nature Communications 12, 2723 (2021).


[3 - 2021] D. M. Burn, R. Brearton, K. J. Ran, S. L. Zhang, G. van der Laan, T. Hesjedal, Periodically modulated skyrmion strings in Cu2OSeO3, npj Quantum Materials 6, 73 (2021).


[4 - 2021] D. M. Burn, S. L. Zhang, G. v. d. Laan, T. Hesjedal, Magnetization dynamics in ordered spin structures revealed by diffractive and reflectometry ferromagnetic resonance, AIP Advances 11, 015327 (2021).


[5 - 2021] S. P. M. Curley, B. M. Huddart, D. Kamenskyi, M. J. Coak, R. C. Williams, S. Ghannadzadeh, A. Schneider, S. Okubo, T. Sakurai, H. Ohta, J. P. Tidey, D. Graf, S. J. Clark, S. J. Blundell, F. L. Pratt, M. T. F. Telling, T. Lancaster, J. L. Manson, P. A. Goddard, Anomalous magnetic exchange in a dimerized quantum magnet composed of unlike spin species, Physical Review B 104, 214435 (2021).


[6 - 2021] A. E. Hall, D. D. Khalyavin, P. Manuel, D. A. Mayoh, F. Orlandi, O. A. Petrenko, M. R. Lees, G. Balakrishnan, Magnetic structure investigation of the intercalated transition metal dichalcogenide V1/3NbS2, Physical Review B 103, 174431 (2021).


[7 - 2021] T. J. Hicken, M. N. Wilson, K. J. A. Franke, B. M. Huddart, Z. Hawkhead, M. Gomilšek, S. J. Clark, F. L. Pratt, A. Štefančič, A. E. Hall, M. Ciomaga Hatnean, G. Balakrishnan, T. Lancaster, Megahertz dynamics in skyrmion systems probed with muon-spin relaxation, Physical Review B 103, 024428 (2021).


[8 - 2021] S. J. R. Holt, C. Ritter, M. R. Lees, G. Balakrishnan, Investigation of the magnetic ground state of GaV4S8 using powder neutron diffraction, Journal of Physics: Condensed Matter 33, 255802 (2021).


[9 - 2021] S. J. R. Holt, A. Štefančič, J. C. Loudon, M. R. Lees, G. Balakrishnan, Investigations of the size distribution and magnetic properties of nanoparticles of Cu2OSeO3, Materials Research Express 8, 116101 (2021).


[10 - 2021] B. M. Huddart, M. Gomilšek, T. J. Hicken, F. L. Pratt, S. J. Blundell, P. A. Goddard, S. J. Kaech, J. L. Manson, T. Lancaster, Magnetic order and ballistic spin transport in a sine-Gordon spin chain, Physical Review B 103, L060405 (2021).


[11 - 2021] G. v. d. Laan, S. L. Zhang, T. Hesjedal, Depth profiling of 3D skyrmion lattices in a chiral magnet—A story with a twist, AIP Advances 11, 015108 (2021).


[12 - 2021] S. Mañas-Valero, B. M. Huddart, T. Lancaster, E. Coronado, F. L. Pratt, Quantum phases and spin liquid properties of 1T-TaS2, npj Quantum Materials 6, 69 (2021).


[13 - 2021] D. A. Mayoh, G. D. A. Wood, S. J. R. Holt, G. Beckett, E. J. L. Dekker, M. R. Lees, G. Balakrishnan, Effects of Fe Deficiency and Co Substitution in Polycrystalline and Single Crystals of Fe3GeTe2, Crystal Growth & Design 21, 6786-6792 (2021).


[14 - 2021] S. H. Moody, P. Nielsen, M. N. Wilson, D. A. Venero, A. Štefančič, G. Balakrishnan, P. D. Hatton, Experimental evidence of a change of exchange anisotropy sign with temperature in Zn-substituted Cu2OSeO3, Physical Review Research 3, 043149 (2021).


[15 - 2021] K. Ran, Y. Liu, Y. Guang, D. M. Burn, G. van der Laan, T. Hesjedal, H. Du, G. Yu, S. Zhang, Creation of a Chiral Bobber Lattice in Helimagnet-Multilayer Heterostructures, Physical Review Letters 126, 017204 (2021).


[16 - 2021] L. A. Turnbull, M. T. Birch, A. Laurenson, N. Bukin, E. O. Burgos-Parra, H. Popescu, M. N. Wilson, A. Stefančič, G. Balakrishnan, F. Y. Ogrin, P. D. Hatton, Tilted X-Ray Holography of Magnetic Bubbles in MnNiGa Lamellae, ACS Nano 15, 387-395 (2021).


[17 - 2021] M. N. Wilson, T. J. Hicken, M. Gomilšek, A. Štefančič, G. Balakrishnan, J. C. Loudon, A. C. Twitchett-Harrison, F. L. Pratt, M. Telling, T. Lancaster, Spin dynamics in bulk MnNiGa and Mn1.4Pt0.9Pd0.1Sn investigated by muon spin relaxation, Physical Review B 104, 134414 (2021).


[18 - 2021] T. B. Winkler, K. Litzius, A. de Lucia, M. Weißenhofer, H. Fangohr, M. Kläui, Skyrmion States in Disk Geometry, Physical Review Applied 16, 044014 (2021).




Publications 2022


[1 - 2022] B. Achinuq, R. Fujita, W. Xia, Y. Guo, P. Bencok, G. van der Laan, T. Hesjedal, Covalent Mixing in the 2D Ferromagnet CrSiTe3 Evidenced by Magnetic X-Ray Circular Dichroism, Physica Status Solidi (RRL) – Rapid Research Letters 16, 2100566 (2022).

[2 - 2022] G. Awana, R. Fujita, A. Frisk, P. Chen, Q. Yao, A. J. Caruana, C. J. Kinane, N. J. Steinke, S. Langridge, P. Olalde-Velasco, S. S. Dhesi, G. van der Laan, X. F. Kou, S. L. Zhang, T. Hesjedal, D. Backes, Critical analysis of proximity-induced magnetism in MnTe/Bi2Te3 heterostructures, Physical Review Materials 6, 053402 (2022).

[3 - 2022] M. Beg, M. Lang, H. Fangohr, Ubermag: Toward More Effective Micromagnetic Workflows, IEEE Transactions on Magnetics 58, 7300205 (2022).

[4 - 2022] M. T. Birch, D. Cortés-Ortuño, K. Litzius, S. Wintz, F. Schulz, M. Weigand, A. Štefančič, D. A. Mayoh, G. Balakrishnan, P. D. Hatton, G. Schütz, Toggle-like current-induced Bloch point dynamics of 3D skyrmion strings in a room temperature nanowire, Nature Communications 13, 3630 (2022).

[5 - 2022] M. T. Birch, L. Powalla, S. Wintz, O. Hovorka, K. Litzius, J. C. Loudon, L. A. Turnbull, V. Nehruji, K. Son, C. Bubeck, T. G. Rauch, M. Weigand, E. Goering, M. Burghard, G. Schütz, History-dependent domain and skyrmion formation in 2D van der Waals magnet Fe3GeTe2, Nature Communications 13, 3035 (2022).

[6 - 2022] R. Fujita, P. Bassirian, Z. Li, Y. Guo, M. A. Mawass, F. Kronast, G. van der Laan, T. Hesjedal, Layer-Dependent Magnetic Domains in Atomically Thin Fe5GeTe2, ACS Nano 16, 10545-10553 (2022).

[7 - 2022] R. Fujita, J. Liu, X. Hou, Y. Guo, J. Herrero-Martín, G. van der Laan, T. Hesjedal, X-ray spectroscopy for the magnetic study of the van der Waals ferromagnet CrSiTe3 in the few- and monolayer limit, 2d Materials 9, 045007 (2022).

[8 - 2022] A. E. Hall, J. C. Loudon, P. A. Midgley, A. C. Twitchett-Harrison, S. J. R. Holt, D. A. Mayoh, J. P. Tidey, Y. Han, M. R. Lees, G. Balakrishnan, Comparative study of the structural and magnetic properties of Mn1/3NbS2 and Cr1/3NbS2, Physical Review Materials 6, 024407 (2022).

[9 - 2022] T. J. Hicken, Z. Hawkhead, M. N. Wilson, B. M. Huddart, A. E. Hall, G. Balakrishnan, C. Wang, F. L. Pratt, S. J. Clark, T. Lancaster, Energy-gap driven low-temperature magnetic and transport properties in Cr1/3MS2 (M = Nb, Ta), Physical Review B 105, L060407 (2022).

[10 - 2022] T. J. Hicken, M. N. Wilson, S. J. R. Holt, R. Khassanov, M. R. Lees, R. Gupta, D. Das, G. Balakrishnan, T. Lancaster, Magnetism in the N\'eel-skyrmion host GaV4S8 under pressure, Physical Review B 105, 134414 (2022).

[11 - 2022] D. A. Mayoh, J. Bouaziz, A. E. Hall, J. B. Staunton, M. R. Lees, G. Balakrishnan, Giant topological and planar Hall effect in Cr1/3NbS2, Physical Review Research 4, 013134 (2022).

[12 - 2022] K. Ran, Y. Liu, H. Jin, Y. Shangguan, Y. Guang, J. Wen, G. Yu, G. van der Laan, T. Hesjedal, S. Zhang, Axially Bound Magnetic Skyrmions: Glueing Topological Strings Across an Interface, Nano Letters 22, 3737-3743 (2022).

[13 - 2022] L. A. Turnbull, M. T. Littlehales, M. N. Wilson, M. T. Birch, H. Popescu, N. Jaouen, J. A. T. Verezhak, G. Balakrishnan, P. D. Hatton, X-ray holographic imaging of magnetic surface spirals in FeGe lamellae, Physical Review B 106, 064422 (2022).

[14 - 2022] A. C. Twitchett-Harrison, J. C. Loudon, R. A. Pepper, M. T. Birch, H. Fangohr, P. A. Midgley, G. Balakrishnan, P. D. Hatton, Confinement of Skyrmions in Nanoscale FeGe Device-like Structures, ACS Applied Electronic Materials DOI 10.1021/acsaelm.2c00692 (2022).