Research challenge 1: skyrmion materials

Research challenge 1: Skyrmion materials

Research Challenge 1 concerns the synthesis and characterization of skyrmionic materials. Polycrystalline and single-crystals of skyrmion materials are produced using a range of techniques.

In the study of skyrmion lattices, one class of materials has occupied a prominent place in the literature: crystals that adopt the P213 space group (or B20 phase). The first systems identified were a group of transition metal compounds, all of which lack space-inversion symmetry and host the Dzyaloshinskii-Moriya (DM) interaction. Examples of this class are FeGe/Si, Fe1-xCoxSi and MnSi. An interesting example of the B20 type materials that is not metallic is the magneto-electric Cu2OSeO3, also exhibiting helimagnetic order. It has a much more complex unit cell, with the Cu building blocks of which offer opportunities to tune the structure-property relationship observed in the variety of B20 structures.

In our programme of materials preparation we have grown examples of B20 materials. In addition to the B20's, there are other related structures such as the βMn types that may host exotic magnetic objects and allow the study of skyrmion lattices and related phenomena. The search for new materials that exhibit skyrmion lattices has been a significant part of our materials research in the programme. We have investigated compounds that exhibit chiral/helical magnetic ordering or alternatively, a ferromagnetic phase that can be switched to a helimagnetic phase.

A 2-mirror optical furnace used for crystal growth at Warwick

Polycrystalline materials synthesis and single-crystal growth

Much of the synthesis of polycrystalline samples and single-crystals of skymion hosting materials is carried out in the Physics Department at the University of Warwick, whose Superconductivity and Magnetism Group has excellent facilities for research into skyrmionic materials. Warwick is well-known for the growth of high-quality single-crystals of oxides, intermetallics and related materials, with over 50 national and international partners engaged with this work. It is equipped with three optical mirror furnaces (including one with Xe arc lamps which uniquely allows us to reach temperatures of up to 2800 °C), a tetra-arc furnace, as well as facilities for crystal growth by the Bridgman method, the flux method, and chemical vapor transport.

Polycrystalline materials; Polycrystalline samples of new and interesting materials are prepared using a suite of box and annealing furnaces.

Optical mirror furnaces We employ either the Floating Zone (FZ) or Solvent Floating Zone (TSFZ) techniques to grow single crystals. The different optical furnaces provide a range of preparation conditions allowing us to vary, for example, the temperature definition in the molten zone and the growth rates. A wide variety of systems, which have both congruent and incongruent melting points can be prepared using these methods. Different growth atmospheres and pressures can be used. Materials that have been prepared include oxides as well as intermetallic materials.

Flux technique: Suitable flux materials for the materials under study are chosen from an analysis of the phase diagrams.

Bridgman and vapor transport methods For some materials, the Bridgman or vapor transport growth techniques are more suitable. In the Bridgman method the material is contained in a crucible, e.g. a sealed quartz ampoule or a boron nitride crucible, and cooled from the molten state through a temperature gradient. For crystals that cannot be obtained from molten material, the chemical vapor transport (CVT) technique can be used. This is the most popular technique to obtain several skyrmion materials.



Schematic of the 2-zone growth using the chemical vapour transport technique. Here, the precursor material is mixed with a transporting agent (such as iodine or chlorine) and placed in an evacuated sealed quartz tube. A furnace with a hot zone at temperature T2 heats a precursor, that is then transported to a colder zone T1 where it is deposited as crystals. These growths typically last for several weeks for each growth, and the growth periods and conditions have to be optimized for each material.

Single crystals of several pure and doped systems hosting skyrmions have been prepared using CVT.


Single crystals of Cu2OSeO3 were grown from pre-reacted polycrystalline powder using chemical vapor transport with TeCl4 as a transporting agent. The skymion lattices was studied using x-rays (a) Schematic diagram of the experimental setup. (b) Small-angle x-ray scattering pattern of the helical state of Cu2OSeO3. (c) Energy scan of x-ray transmission (blue) and magnetic scattering (red) for a 200-nm-thick Cu2OSeO3 lamella at 20 K and zero magnetic field, aligned with the incoming beam ∥ [110]. Representative transmitted intensity was determined by summing inside the blue circle on (b), and the scattered intensity was taken by summing the red circles and subtracting the green circles as background [18 -2020].

Studies of skyrmion materials in the laboratory

The materials that have been prepared are characterized in the laboratories of the Skyrmion Project partners. Structural studies include x-ray diffraction and electron microscopy. Samples are also analyzed using thermogravimetric and differential thermal analysis. A real-time x-ray Laue back reflection system at Warwick allows fast, direct examination of the quality of the as-grown single crystals and the alignment and cutting of samples.


Comparative study of the structural and magnetic properties of single crystals of Mn1/3NbS2 and Cr1/3NbS2 (a) Unit cell of Mn1/3NbS2 or Cr1/3NbS2 viewed down the [001] direction. (b) Simulated electron diffraction patterns along the [001] direction for both the noncentrosymmetric P6322 structure and the centrosymmetric P63/mmc structure, which differ from each other in the relative intensities of key spots (200) and (030), assuming kinematic scattering. An electron micrograph (c) of a crystal of Mn1/3NbS2 and an electron diffraction pattern from the same area are shown and match well with the simulation for the P6322 space group, with the especially faint (200) spot marked with an arrow. (d) The unit cell viewed along [100] direction. (e) A simulation of the corresponding electron diffraction pattern. (f) Bright-field images and electron diffraction patterns from Cr1/3NbS2 and (g) Mn1/3NbS2. While the Cr1/3NbS2 pattern matches well with the simulation, Mn1/3NbS2 displays extra reflections indicating a superlattice with a period of 3c in the c direction and 7d010 in the b direction [8 -2022].

In-depth experimental studies are carried out at all the Skymion Project host institutions using a range of probes including AC and DC magnetic measurements, specific heat studies, transport measurements (resistivity, Hall effect, thermopower), as a function of temperature, magnetic field, and pressure. We have facilities for magnetometry, transport, and thermodynamic measurements from 50 mK to 800 K in magnetic fields up to 17 T. Transport (30 kbar) and magnetization (10 kbar) studies can also be carried out as a function of pressure.


Real component of AC susceptibility in constant field Bext for GaV4S8-ySey where (a) y = 0 (b) y = 0.1, (c) y = 8, and (d) y = 7.9. Dashed black lines indicate fields where μSR measurements were performed with white highlighting proposed skyrmion lattice regions. [11 -2020].

The materials we have prepared are used for further studies by members of the Skymion Project under Research Challenge 2 and Research Challenge 3.

At Cambridge University advanced microcopy techniques are used to investigate materials right down the level of an individual skyrmion.

Samples are used for experiments at central facilities, both here in the UK at ISIS and Diamond, as well at international facilities such as PSI, ILL, ESRF and SOLEIL.

Pressure stability of the skyrmion lattice in Cu2OSeO3 in the μ0H parallel ki geometry. Small angle neutron scattering (SANS) patterns of the skyrmion lattice at T = 56 K, μ0H = 25 mT, and (a) ambient pressure or (b) P = 5 kbar. (c) and (d) show SANS patterns obtained at ambient pressure and P = 5 kbar, respectively, each with fixed T = 58.5 K, μ0H = 21 mT [9 - 2020].

Single crystals have also been shared with collaborators both here in the UK and overseas for studies complementary to those of the Skyrmion Project team.




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).