A5036064094- Advanced Condensed Matter Physics
- Magnetic and transport properties of perovskites and related materials
- Physics of Superconductivity and Magnetism
- Magnetic properties of thin films
- Rare-earth and actinide compounds
- Iron-based superconductors research
- Crystallization and Solubility Studies
- Multiferroics and related materials
- X-ray Diffraction in Crystallography
- Magnetic Properties of Alloys
- Magnetic Properties and Applications
- Nuclear materials and radiation effects
- Topological Materials and Phenomena
- Superconducting Materials and Applications
- ZnO doping and properties
- Crystal Structures and Properties
- Characterization and Applications of Magnetic Nanoparticles
- Nuclear physics research studies
- 2D Materials and Applications
- Geomagnetism and Paleomagnetism Studies
- Metallic Glasses and Amorphous Alloys
- Inorganic Chemistry and Materials
- Copper-based nanomaterials and applications
- Superconductivity in MgB2 and Alloys
- Muon and positron interactions and applications
Durham University
2018-2025
Memorial University of Newfoundland
2022-2025
McMaster University
2015-2020
Dalhousie University
2012-2017
Quantum Science Center
2017
This paper reports on magnetometry and magnetoresistance measurements of MnSi epilayers performed in out-of-plane magnetic fields. We present a theoretical analysis the chiral modulations that arise confined cubic helimagnets where uniaxial anisotropy axis field are both out-of-plane. In contrast to in-plane [Wilson et al., Phys. Rev. B 86, 144420 (2012)], hard-axis MnSi/Si(111) increases energy (111)-oriented skyrmions helicoids relative cone phase, it makes phase only stable texture below...
Magnetic skyrmions are topologically nontrivial particles with a potential application as information elements in future spintronic device architectures. While they commonly portrayed two dimensional objects, reality magnetic thought to exist elongated, tube-like objects extending through the thickness of sample. Study this skyrmion tube (SkT) state is highly relevant for investigating metastability and implementation recently proposed magnonic computing. However, direct experimental imaging...
Skyrmions are particlelike vortices of magnetization with nontrivial topology, which usually stabilized by Dzyaloshinskii-Moriya interactions (DMI) in noncentrosymmetric bulk materials. Exceptions centrosymmetric Gd- and Eu-based skyrmion-lattice (SL) hosts zero DMI, where both the SL stabilization mechanisms magnetic ground states remain controversial. We address these here investigating static dynamical spin properties host <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"...
In epitaxial MnSi/Si(111) films, the in-plane magnetization saturation is never reached due to formation of specific surface chiral modulations with propagation direction perpendicular film surfaces [Wilson et al., Phys. Rev. B 88, 214420 (2013)]. this paper we show that occurrence such twists a general effect attributed all bulk and confined magnetic crystals lacking inversion symmetry. We present experimental investigations phenomenon in nanolayers supported by detailed theoretical...
Magnetoresistance (MR), polarized neutron reflectometry (PNR), and magnetometry measurements in MnSi thin films rigorous analytical solutions of the micromagnetic equations show that field-induced unwinding confined helicoids occurs via discrete steps. A comparison between theoretical results PNR data shows finite-size effects confine wavelength lead to a quantization number turns helicoid. We demonstrate magnetic state these finite can be read by electrical means.
A detailed investigation of the magnetization processes in epitaxial MnSi thin film reveals existence elliptically distorted skyrmion strings that lie plane film. We provide proof uniaxial anisotropy stabilizes this state over extended regions magnetic phase diagram. Theoretical analysis an observed cascade first-order transitions is based on rig- orous numerical calculations competing chiral modulations, which shows helicoids, elliptic skyrmions, and cone phases.
Previous observations of metastable magnetic skyrmions have shown that close to the equilibrium pocket state has a short lifetime, and therefore rapid cooling is required generate significant skyrmion population at low temperatures. Here, we report lifetime in Cu$_2$OSeO$_3$ extended by factor 50 with introduction only 2.5% zinc doping, allowing over 50% survive when field-cooling rate just 1 K/min. Our systematic study suggests enhancement due removal spins non-magnetic dopant, which...
Double perovskites (DP) of the general formula Ba2MReO6, where M = Mg, Zn, and Y2/3, all based on Re6+ (5d1, t2g1), were synthesized studied using magnetization, heat capacity, muon spin relaxation, neutron-scattering techniques. All are cubic, Fm3̅m, at ambient temperature to within resolution X-ray neutron diffraction data, although data suggest possibility a local distortion for Mg. The Mg DP is ferromagnet, Tc 18 K, with saturation moment ∼0.3 bohr magnetons 3 K. There two anomalies in...
Metal-to-insulator transitions (MITs) are a dramatic manifestation of strong electron correlations in solids1. The insulating phase can often be suppressed by quantum tuning, i.e. varying nonthermal parameter such as chemical composi- tion or pressure, resulting zero-temperature transition (QPT) to metallic state driven fluctuations, contrast conventional thermal fluctuations. Theories exotic phenomena known occur near the Mott QPT criticality and high-temperature superconductivity assume...
Mixed spin-singlet and spin-triplet pairing can occur in noncentrosymmetric superconductors. In this respect, a comprehensive characterization of the superconductor BeAu was carried out. It established that undergoes structural phase transition from low-temperature FeSi structure type to high-temperature centrosymmetric CsCl at ${T}_{\text{s}}=860$ K. The modification exhibits superconducting below ${T}_{\text{c}}=3.3$ values lower (${H}_{\text{c1}}=32$ Oe) upper (${H}_{\text{c2}}=335$...
We report neutron scattering and muon spin relaxation measurements (muSR) on the pyrochlore antiferromagnet Yb2Ge2O7. Inelastic was used to probe transitions between crystal electric field levels, allowing us determine eigenvalues eigenvectors appropriate J=7/2 Yb3+ ion in this environment. The ground state doublet Yb2Ge2O7 corresponds primarily m_J = +/- 1/2 with local XY anisotropy, consistent an S_eff description for Yb moments. muSR reveal presence of ordering transition at T_N 0.57 K...
We present Hall-effect measurements on MnSi/Si(111) epilayers and find an anomalous Hall contribution that is significantly smaller than in bulk crystals, which enables the observation of additional to signal previously overlooked MnSi. Our indicate not due skyrmions MnSi thin films, are absent out-of-plane fields, but rather result scattering from cone phase. The absence magnetic contrast transmission electron microscopy (TEM) consistent with this interpretation [T. L. Monchesky et al.,...
Three closely related double perovskites (DP) based on the $5{d}^{2}$ ion, $\mathrm{O}{\mathrm{s}}^{6+},\mathrm{B}{\mathrm{a}}_{2}M\mathrm{Os}{\mathrm{O}}_{6}$, with $M=\mathrm{Mg}$, Zn, and Cd have been prepared characterized using x-ray (XRD) neutron diffraction (ND), dc magnetization, heat capacity, muon spin relaxation $(\ensuremath{\mu}\mathrm{SR})$ techniques. All three are cubic, Fm-$3m$, at ambient temperature from XRD...
We present muon spin rotation and relaxation $(\ensuremath{\mu}\mathrm{SR})$ measurements as well demagnetizing-field-corrected magnetization on polycrystalline samples of the noncentrosymmetric superconductor BeAu. From $\ensuremath{\mu}\mathrm{SR}$ in a transverse field, we determine that BeAu is type-I with H${}_{c}=$ 258 Oe, amending previous understanding compound type-II superconductor. To account for demagnetizing effects measurements, produce an ellipsoidal sample, which...
<a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:msub><a:mi>Eu</a:mi><a:mn>5</a:mn></a:msub><a:msub><a:mi>In</a:mi><a:mn>2</a:mn></a:msub><a:msub><a:mi>Sb</a:mi><a:mn>6</a:mn></a:msub></a:mrow></a:math> is a member of family orthorhombic nonsymmorphic rare-earth intermetallics that combines large localized magnetic moments and itinerant exchange with low carrier density perpendicular glide planes. This may result in special topological crystalline (wallpaper fermion) or axion...
Chiral magnetic thin films have been a recent source of interest due to their ability stabilize topological states, known as skyrmions. However, there exists disagreement in the literature over existence epitaxial MnSi films, grown on Si(111) substrates. The authors combined polarized neutron reflectometry and small-angle uncover direct evidence for unique skyrmion geometry MnSi/Si(111) where core magnetization vortex-like textures points plane film.
We present an investigation into the structural and magnetic properties of Zn-substituted ${\mathrm{Cu}}_{2}{\mathrm{OSeO}}_{3}$, a system in which skyrmion lattice (SkL) phase field--temperature diagram was previously seen to split as function increasing Zn concentration. find that splitting SkL is only observed polycrystalline samples reflects occurrence several coexisting phases with different content, each distinguished by behavior. No such multiphase behavior single-crystal samples.
We report small-angle neutron scattering (SANS) measurements of the skyrmion lattice in ${({\mathrm{Cu}}_{0.976}{\mathrm{Zn}}_{0.024})}_{2}{\mathrm{OSeO}}_{3}$ under application electric and magnetic fields. These show an expansion stability region with field. Furthermore, using time-resolved SANS, we observe slow formation skyrmions after or field is applied, which has not been observed pristine ${\mathrm{Cu}}_{2}{\mathrm{OSeO}}_{3}$ crystals. The measured times are dramatically longer than...
We examine the crystal structures and magnetic properties of several S = 1 Ni(II) coordination compounds, molecules polymers, that include bridging ligands HF2−, AF62− (A Ti, Zr) pyrazine or non-bridging F−, SiF62−, glycine, H2O, 1-vinylimidazole, 4-methylpyrazole 3-hydroxypyridine. Pseudo-octahedral NiN4F2, NiN4O2 NiN4OF cores consist equatorial Ni-N bonds are equal to slightly longer than axial Ni-Lax bonds. By design, zero-field splitting (D) is large in these systems and, presence...
We use neutron diffraction and muon spin relaxation to study the effect of in-plane uniaxial pressure on antiferromagnetic (AF) orthorhombic phase in BaFe$_2$As$_2$ its Co- Ni-substituted members near optimal superconductivity. In low temperature AF ordered state, necessary detwin crystals also increases magnetic moment, reaching an 11$\%$ increase under 40 MPa for BaFe$_{1.9}$Co$_{0.1}$As$_2$, a 15$\%$ BaFe$_{1.915}$Ni$_{0.085}$As$_2$. observe ordering ($T_N$) about 0.25 K/MPa all...
The gadolinium pyrochlores ${\mathrm{Gd}}_{2}{B}_{2}{\mathrm{O}}_{7}$ are among the best realizations of antiferromagnetically coupled Heisenberg spins on a pyrochlore lattice. We present magnetic characterization ${\mathrm{Gd}}_{2}{\mathrm{Pt}}_{2}{\mathrm{O}}_{7}$, unique member this family. Magnetic susceptibility, heat capacity, and muon spin relaxation measurements show that ${\mathrm{Gd}}_{2}{\mathrm{Pt}}_{2}{\mathrm{O}}_{7}$ undergoes an antiferromagnetic ordering transition at...
Four new double perovskites, SrLaMReO(6) (M = Mg, Mn, Co, Ni) in which Re(5+) (5d(2)) is present, were prepared via conventional solid state reactions and characterized by X-ray neutron powder diffraction, XANES, SQUID magnetometry, muon spin relaxation (μSR). Synchrotron diffraction experiments confirmed that all compounds crystallize the monoclinic P2(1)/n structure type, consists of alternately corner-shared octahedra MO(6) ReO(6). Rietveld refinement results indicated anti-site mixing...
We present muon spin rotation ($\mu$SR) and susceptibility measurements on single crystals of isoelectronically doped URu$_{2-x}$T$_x$Si$_2$ (T = Fe, Os) for doping levels up to 50\%. Zero Field (ZF) $\mu$SR show long-lived oscillations demonstrating that an antiferromagnetic state exists down low both Os Fe dopants. The further increase in the internal field with Os. Comparison local moment - hybridization crossover temperature from our magnetic transition shows changes hybridization,...
Nanoscopic lamellae of centrosymmetric ferromagnetic alloys have recently been reported to host the biskyrmion spin texture; however, this has disputed as misidentication topologically trivial type-II magnetic bubbles. Here we demonstrate resonant soft X-ray holographic imaging topological states in alloy (Mn1–xNix)0.65Ga0.35 (x = 0.5), showing presence stripes evolving into single core We observe rotation stripe phase via nucleation and destruction disclination defects. This indicates...
We present longitudinal-field muon-spin relaxation (LF $\mu$SR) measurements on two systems that stabilize a skyrmion lattice (SkL): Cu$_2$OSeO$_3$, and Co$_x$Zn$_y$Mn$_{20-x-y}$ for $(x,y)~=~(10,10)$, $(8,9)$ $(8,8)$. find the SkL phase of Cu$_2$OSeO$_3$ exhibits emergent dynamic behavior at megahertz frequencies, likely due to collective excitations, allowing be identified from $\mu$SR response. From following different cooling protocols calculations muon stopping site, we suggest...