document

Tilted Spirals and Low-temperature Skyrmions in Cu₂OSeO₃

Crisanti, M. (author), Leonov, A. O. (author), Cubitt, R. (author), Labh, A. (author), Wilhelm, H. (author), Schmidt, M. P. (author), Pappas, C. (author)

journal article 2023

document

Tilted spirals and low-temperature skyrmions in Cu2OSeO3

Crisanti, M. (author), Leonov, A. O. (author), Cubitt, R. (author), Labh, A. (author), Wilhelm, H. (author), Schmidt, Marcus P. (author), Pappas, C. (author)

The bulk helimagnet Cu2OSeO3 represents a unique example in the family of B20 cubic helimagnets exhibiting a tilted spiral and skyrmion phase at low temperatures when the magnetic field is applied along the easy (001) crystallographic direction. Here we present a systematic study of the stability and ordering of these low-temperature magnetic...

journal article 2023

document

Reorientation processes of tilted skyrmion and spiral states in a bulk cubic helimagnet Cu₂OSeO₃

Leonov, Andrey O. (author), Pappas, C. (author)

We present a systematic study of tilted spiral states obtained theoretically within the classical Dzyaloshinskii model for magnetic states in cubic non-centrosymmetric ferromagnets. Such tilted spirals are shown to stabilize under the competing effect of cubic and exchange anisotropies inherent to cubic helimagnets. By focusing on the...

journal article 2023

document

Magnetic phase diagram and cluster glasslike properties of stage-1 graphite-intercalated FeCl3

Levinsky, J. J.B. (author), Scholtens, R. (author), Pappas, C. (author), Blake, G. R. (author)

We present a comprehensive investigation of the magnetic properties of stage-1 graphite intercalated FeCl3 using a combination of DC and AC magnetic susceptibility, thermoremanent magnetization, and field-dependent magnetization measurements. This van der Waals system, with a centrosymmetric honeycomb lattice, combines frustration and...

journal article 2022

document

Radial spin echo small-angle neutron scattering method: concept and performance

Kadletz, E. (author), Bouwman, W.G. (author), Pappas, C. (author)

A novel spin echo small-angle neutron scattering (SESANS) concept based on a rotationally symmetric magnetic field geometry is introduced. The proposed method is similar to the conventional linear SESANS technique but uses<br/>longitudinal precession fields and field gradients in a radial direction, as typically found in neutron spin echo (NSE)...

journal article 2022

document

Topological boundaries between helical domains as a nucleation source of skyrmions in the bulk cubic helimagnet Cu2OSeO3

Leonov, A. O. (author), Pappas, C. (author)

Cu2OSeO3 represents a unique example in the family of B20 cubic helimagnets with a tilted spiral and a low-temperature skyrmion phase arising for magnetic fields applied along the easy crystallographic (100) axes. Although the stabilization mechanism of these phases can be accounted for by cubic magnetic anisotropy, the skyrmion nucleation...

journal article 2022

document

Evolution of helimagnetic correlations when approaching the quantum critical point of Mn1-xFexSi

Pappas, C. (author), Leonov, A.O. (author), Bannenberg, L.J. (author), Fouquet, P (author), Wolf, T. (author), Weber, F (author)

We present a comprehensive investigation of the evolution of helimagnetic correlations in Mn1−xFexSi with increasing doping. By combining polarized neutron scattering and high resolution neutron spin echo spectroscopy we investigate three samples with x = 0.09, 0.11, and 0.14, i.e., with compositions on both sides of the concentration x∗∼0.11...

journal article 2021

document

Field-driven metamorphoses of isolated skyrmions within the conical state of cubic helimagnets

Leonov, Andrey O. (author), Pappas, C. (author), Smalyukh, Ivan I. (author)

Topologically stable field configurations appear in many fields of physics, from elementary particles to condensed matter and cosmology. Deep physical relations and common physical features of a large variety of very different solitonic states in these systems arise from the mathematical similarity of phenomenological equations.<br/>During the...

journal article 2021

document

Field-induced vortex-like textures as a probe of the critical line in reentrant spin glasses

Martin, N. (author), Bannenberg, L.J. (author), Deutsch, M. (author), Pappas, C. (author), Chaboussant, G. (author), Cubitt, R. (author), Mirebeau, I. (author)

We study the evolution of the low-temperature field-induced magnetic defects observed under an applied magnetic field in a series of frustrated amorphous ferromagnets (Fe₁_-_xMn_x)₇₅P₁₆B₃Al₃ (“a-Fe₁_-_xMn_x”)....

journal article 2021

document

Phase-transformation and precipitation kinetics in vanadium micro-alloyed steels by in-situ, simultaneous neutron diffraction and SANS

Ioannidou, C. (author), Navarro Lopez, A. (author), Dalgliesh, Robert M. (author), Rijkenberg, Arjan (author), Geerlofs, N. (author), Pappas, C. (author), Sietsma, J. (author), van Well, A.A. (author), Offerman, S.E. (author)

In-situ Neutron Diffraction and Small-Angle Neutron Scattering (SANS) are employed for the first time simultaneously in order to reveal the interaction between the austenite to ferrite phase transformation and the precipitation kinetics during isothermal annealing at 650 and at 700 °C in three steels with different vanadium (V) and carbon (C)...

journal article 2021

document

Field and anisotropy driven transformations of spin spirals in cubic skyrmion hosts

Leonov, A.O. (author), Pappas, C. (author), Kezsmarki, I. (author)

We discuss distinctive features of spiral states in bulk chiral magnets such as MnSi and Cu2OSeO3 that stem from the effect of the cubic magnetocrystalline anisotropy. First of all, at both the helical-to-conical and theconical-to-ferromagnetic transitions, taking place at Hc1 and Hc2, respectively, the cubic anisotropy leads to reversible or...

journal article 2020

document

Furnace for in situ and simultaneous studies of nano-precipitates and phase transformations in steels by SANS and neutron diffraction

Navarro Lopez, A. (author), Ioannidou, C. (author), van der Wal, E.M. (author), Arechabaleta Guenechea, Z. (author), van den Oever, R. (author), Verleg, M.N. (author), Dalgliesh, R. M. (author), Sykora, J. (author), Akeroyd, F. A. (author), Geerlofs, N. (author), Sietsma, J. (author), Pappas, C. (author), van Well, A.A. (author), Offerman, S.E. (author)

Interphase precipitation occurring during solid-state phase transformations in micro-alloyed steels is generally studied through transmission electron microscopy, atom probe tomography, and ex situ measurements of Small-Angle Neutron Scattering (SANS). The advantage of SANS over the other two characterization techniques is that SANS allows...

journal article 2020

document

Analysis of SESANS data by numerical Hankel transform implementation in SasView

Bakker, J.H. (author), Washington, Adam L. (author), Parnell, S.R. (author), van Well, A.A. (author), Pappas, C. (author), Bouwman, W.G. (author)

SESANS data analysis has been implemented in the SasView software package, allowing SESANS experiments to be analyzed using a numerical Hankel transformation of isotropic small-angle scattering (SAS) models. The error of the numerical approximation is three orders of magnitude below typical experimental errors. All advanced data fitting...

journal article 2020

document

Semi-analytical calculations of intrinsic field magnetic field inhomogeneities for a Neutron Spin Echo spectrometer at the ESS

Kusmin, A. (author), Pappas, C. (author)

Neutron Spin Echo methods (NSE) use Larmor labelling to measure the precession phase of the neutron beam polarization around well-defined magnetic fields. Scattering by a sample can affect the resulting precession phase providing information on the sample's structure and dynamics with high accuracy and resolution. A major limitation for the...

journal article 2020

document

Evolution of the precipitate composition during annealing of vanadium micro-alloyed steels by in-situ SANS

Ioannidou, C. (author), Navarro Lopez, A. (author), Rijkenberg, Arjan (author), Dalgliesh, Robert M. (author), Koelling, Sebastian (author), Pappas, C. (author), Sietsma, J. (author), van Well, A.A. (author), Offerman, S.E. (author)

In-situ Small-Angle Neutron Scattering (SANS) is used to determine the time evolution of the chemical composition of precipitates at 650 °C and 700 °C in three micro-alloyed steels with different vanadium (V) and carbon (C) concentrations. Precipitates with a distribution of substoichiometric carbon-to-metal ratios are measured in all steels....

journal article 2020

document

Multiple low-temperature skyrmionic states in a bulk chiral magnet

Bannenberg, L.J. (author), Wilhelm, Heribert (author), Cubitt, Robert (author), Labh, A. (author), Schmidt, Marcus P. (author), Lelievre-Berna, Eddy (author), Pappas, C. (author), Mostovoy, Maxim (author), Leonov, Andrey O. (author)

Magnetic skyrmions are topologically protected nanoscale spin textures with particle-like properties. In bulk cubic helimagnets, they appear under applied magnetic fields and condense spontaneously into a lattice in a narrow region of the phase diagram just below the magnetic ordering temperature, the so-called A-phase. Theory, however, predicts...

journal article 2019

document

Skyrmion clusters and conical droplets in bulk helimagnets with cubic anisotropy

Leonov, A.O. (author), Pappas, C. (author)

Recent experimental findings in the bulk cubic helimagnet and Mott insulator Cu2OSeO3 highlight the paramount role of cubic anisotropy in stabilizing novel chiral and skyrmion phases. It was indeed found that if a magnetic field is applied along the easy 001 crystallographic direction, competing cubic and<br/>exchange anisotropies tilt the wave...

journal article 2019

document

Fibre formation in calcium caseinate influenced by solvent isotope effect and drying method – A neutron spectroscopy study

Tian, B. (author), Garcia Sakai, Victoria (author), Pappas, C. (author), van der Goot, Atze Jan (author), Bouwman, W.G. (author)

We present an investigation of the dynamics of calcium caseinate as a function of hydration, solvent isotope (H₂O and D₂O) and drying methods (roller drying and spray drying), using quasi-elastic neutron scattering (QENS). These factors are key to the formation of fibres in this material which makes it a potential...

journal article 2019

document

Skyrmions and spirals in MnSi under hydrostatic pressure

Bannenberg, L.J. (author), Sadykov, R. (author), Dalgliesh, R. M. (author), Goodway, C. (author), Schlagel, D. L. (author), Lograsso, T. A. (author), Falus, P. (author), Lelièvre-Berna, E. (author), Pappas, C. (author)

The archetype cubic chiral magnet MnSi is home to some of the most fascinating states in condensed matter, such as skyrmions and a non-Fermi-liquid behavior in conjunction with a topological Hall effect under hydrostatic pressure. Using small angle neutron scattering, we study the evolution of the helimagnetic, conical, and skyrmionic...

journal article 2019

document

Interaction of precipitation with austenite-to-ferrite phase transformation in vanadium micro-alloyed steels

Ioannidou, C. (author), Arechabaleta Guenechea, Z. (author), Navarro Lopez, A. (author), Rijkenberg, Arjan (author), Dalgliesh, Robert M. (author), Kölling, S. (author), Bliznuk, Vitaliy (author), Pappas, C. (author), Sietsma, J. (author), van Well, A.A. (author), Offerman, S.E. (author)

The precipitation kinetics of vanadium carbides and its interaction with the austenite-to-ferrite phase transformation is studied in two micro-alloyed steels that differ in vanadium and carbon concentrations by a factor of two, but have the same vanadium-to-carbon atomic ratio of 1:1. Dilatometry is used for heat-treating the specimens and...

journal article 2019