A5025428477- Advanced Condensed Matter Physics
- Magnetic and transport properties of perovskites and related materials
- Rare-earth and actinide compounds
- Physics of Superconductivity and Magnetism
- Multiferroics and related materials
- Iron-based superconductors research
- Magnetic properties of thin films
- Topological Materials and Phenomena
- ZnO doping and properties
- Magnetic Properties of Alloys
- Inorganic Chemistry and Materials
- High-pressure geophysics and materials
- Electronic and Structural Properties of Oxides
- Magnetic Properties and Applications
- Ferroelectric and Negative Capacitance Devices
- Nuclear materials and radiation effects
- Pigment Synthesis and Properties
- Microwave Dielectric Ceramics Synthesis
- Mesoporous Materials and Catalysis
- Crystallography and Radiation Phenomena
- Perovskite Materials and Applications
- Crystal Structures and Properties
- Organic and Molecular Conductors Research
- Advanced Thermoelectric Materials and Devices
- Analytical Chemistry and Chromatography
Diamond Light Source
2020-2025
University College London
2017-2024
London Centre for Nanotechnology
2017-2024
Rutherford Appleton Laboratory
2024
Brazilian Center for Research in Energy and Materials
2017-2023
Brazilian Synchrotron Light Laboratory
2013-2023
Universidade Estadual de Campinas (UNICAMP)
2011-2022
Argonne National Laboratory
2014-2020
Deutsches Elektronen-Synchrotron DESY
2016-2020
Hospital de Clínicas da Unicamp
2015
A complex iridium oxide β-Li(2)IrO(3) crystallizes in a hyperhoneycomb structure, three-dimensional analogue of honeycomb lattice, and is found to be spin-orbital Mott insulator with J(eff)=1/2 moment. Ir ions are connected the three neighboring via Ir-O(2)-Ir bonding planes, which very likely gives rise bond-dependent ferromagnetic interactions between moments, an essential ingredient Kitaev model spin liquid ground state. Dominant interaction moments indeed confirmed by temperature...
Altermagnetism is a recently identified magnetic symmetry class combining characteristics of conventional collinear ferromagnets and antiferromagnets, that were regarded as mutually exclusive, enabling phenomena functionalities unparalleled in either the two traditional elementary classes. In this work we use symmetry, ab initio theory, experiments to explore x-ray circular dichroism (XMCD) altermagnetic class. As representative material for our XMCD study choose α-MnTe with compensated...
We use resonant elastic x-ray scattering to determine the evolution of magnetic order in ${\mathrm{EuCd}}_{2}{\mathrm{As}}_{2}$ below ${T}_{\mathrm{N}}=9.5$ K, as a function temperature and applied field. find an A-type antiferromagnetic structure with in-plane moments, observe dramatic magnetoresistive effects associated field-induced changes domain populations. Our ab initio electronic calculations indicate that Dirac dispersion found nonmagnetic semimetal...
Transition metal oxides are promising candidates for the next generation of spintronic devices due to their fascinating properties that can be effectively engineered by strain, defects, and microstructure. An excellent example found in ferroelastic LaCoO
Current pulse driven Néel vector rotation in metallic antiferromagnets is one of the most promising concepts antiferromagnetic spintronics. We show microscopically that epitaxial thin films prototypical compound Mn2Au can be reoriented reversibly complete area cross shaped device structures using single current pulses. The resulting domain pattern with aligned staggered magnetization long term stable enabling memory applications. achieve this switching low heating ≈20 K, which regarding fast...
Abstract Here we investigate antiferromagnetic Eu 5 In 2 Sb 6 , a nonsymmorphic Zintl phase. Our electrical transport data show that is remarkably insulating and exhibits an exceptionally large negative magnetoresistance, which consistent with the presence of magnetic polarons. From ab initio calculations, paramagnetic state topologically nontrivial semimetal within generalized gradient approximation (GGA), whereas trivial topological indices obtained using modified Becke−Johnson potential....
We explore the response of Ir $5d$ orbitals to pressure in $\ensuremath{\beta}\ensuremath{-}{\mathrm{Li}}_{2}{\mathrm{IrO}}_{3}$, a hyperhoneycomb iridate proximity Kitaev quantum spin-liquid (QSL) ground state. X-ray absorption spectroscopy reveals reconstruction electronic state below 2 GPa, same range where x-ray magnetic circular dichroism shows an apparent collapse order. The reconstruction, which manifests reduction effective spin-orbit interaction orbitals, pushes...
In antiferromagnetic spintronics, the read-out of staggered magnetization or Neel vector is key obstacle to harnessing ultra-fast dynamics and stability antiferromagnets for novel devices. Here, we demonstrate strong exchange coupling Mn2Au, a unique metallic antiferromagnet that exhibits spin-orbit torques, with thin ferromagnetic Permalloy layers. This allows us benefit from well-estabished methods ferromagnets, while essential advantages spintronics are retained. We show one-to-one...
Crystal geometry can greatly influence the emergent properties of quantum materials. As an example, kagome lattice is ideal platform to study rich interplay between topology, magnetism, and electronic correlation. In this work, combining high-resolution angle-resolved photoemission spectroscopy ab initio calculation, we systematically investigate structure $X{\mathrm{Mn}}_{6}{\mathrm{Sn}}_{6}$ $(X=\mathrm{Dy},\mathrm{Tb},\mathrm{Gd},\mathrm{Y})$ family compounds. We observe Dirac fermion...
Antiferromagnets (AFs) are characterized by spin structures that resistant to external magnetic fields, rendering them ideal for persistent information storage but challenging control. This study demonstrates a thin ferromagnetic adlayer can serve as ‘lever’ provide strong handle on the texture of an adjacent antiferromagnet. In bilayers composed NiO(001) and Co, expected exchange bias effect—a unidirectional shift in Co hysteresis due coupling with NiO—is notably absent. Instead,...
The effect of thermal surface cleaning on the Gilbert damping (α) yttrium iron garnet (YIG), before capping with a metallic layer, has been investigated. Our results show that α is strongly affected by relatively mild annealing conditions (T = 300 °C) when performed in vacuum. This increase needs to be taken into account obtaining spin-mixing conductance from spin pumping measurements. We measure an factor ×8 YIG vacuum annealed at °C. No such changes are observed same temperature 1 × 10−1...
The ability to tune exchange (magnetic) interactions between $3d$ transition metals in perovskite structures has proven be a powerful route discovery of novel properties. Here we demonstrate that the introduction $3d\text{\ensuremath{-}}5d$ pathways double perovskites enables additional tunability, result large spatial extent $5d$ wave functions. Using x-ray probes magnetism and structure at high pressure, show compression ${\mathrm{Sr}}_{2}{\mathrm{FeOsO}}_{6}$ drives an unexpected...
<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...
Lignosulfonate is a colloidal polyelectrolyte that obtained as side product in sulfite pulping. In this work we wanted to study the noncovalent association of colloids different solvents, well find out how charged sulfonate groups are organized on colloid surface. We studied sodium and rubidium lignosulfonate water-methanol mixtures dimethyl formamide. The number average molecular weights Na- Rb-lignosulfonate fractions were 7600 g/mol 9100 g/mol, respectively, polydispersity index for both...
Alkali metals display unexpected properties at high pressure, including emergence of low-symmetry crystal structures, which appear to occur due enhanced electronic correlations among the otherwise nearly free conduction electrons. We investigate high-pressure and structural ground state K, Rb, Cs using x-ray absorption spectroscopy diffraction measurements together with $ab\phantom{\rule{4pt}{0ex}}initio$ theoretical calculations. The sequence phase transitions under pressure observed low...
Resonant inelastic x-ray scattering (RIXS) is an element- and orbital-specific, momentum-resolved technique which couples to multiple degrees of freedom in a material. The field has evolved significantly recent years thanks advances instrumentation. authors present oxygen $K$-edge RIXS data, collected on honeycomb iridate. Clear multiphonon harmonics can be observed, indicative significant electron-phonon coupling (EPC). They conclude that the EPC comparable magnitude found for range 3$d$...
The effect of compression on the magnetic ground state Sr$_2$IrO$_4$ is studied with x-ray resonant techniques in diamond anvil cell. weak interlayer exchange coupling between square-planar 2D IrO$_2$ layers readily modified upon compression, a crossover structures around 7 GPa mimicking an applied field at ambient pressure. Higher pressures drive order-disorder phase transition no order detected above 17-20 GPa. persistence strong interactions $\mathrm{J_{eff}}=1/2$ moments within...
In a combined experimental and theoretical study, we investigate the properties of ${\mathrm{Sr}}_{2}{\mathrm{Ir}}_{1\ensuremath{-}x}{\mathrm{Rh}}_{x}{\mathrm{O}}_{4}$. From branching ratios $L$-edge isotropic x-ray absorption spectra, determine that spin-orbit coupling is remarkably independent $x$ for both iridium rhodium sites. $\text{DFT}+U$ calculations show doping close to isoelectronic introduces impurity bands predominantly character lower Hubbard band. Overlap these two leads...
A pressure-induced collapse of magnetic ordering in $\beta$-Li$_2$IrO$_3$ at $P_m\sim1.5- 2$ GPa has previously been interpreted as evidence for possible emergence spin liquid states this hyperhoneycomb iridate, raising prospects experimental realizations the Kitaev model. Based on structural data obtained \emph{room temperature}, transition is believed to originate small lattice perturbations that preserve crystal symmetry, and related changes bond-directional anisotropic exchange...
We present high-energy x-ray diffraction data under applied pressures up to p = 29 GPa, neutron measurements 1.1 and electrical resistance 5.9 on SrCo2As2. Our demonstrate that there is a first-order transition between the tetragonal (T) collapsed-tetragonal (cT) phases, with an onset above approximately 6 GPa at T 7 K. The pressure for of cT phase range coexistence phases appears be nearly temperature independent. compressibility along a-axis same whereas, c-axis, significantly stiffer,...
Transparent conducting oxides have become ubiquitous in modern optoelectronics. However, the number of that are transparent to visible light and metallic-like conductivity necessary for applications is limited a handful systems been known past 40 years. In this work, we use hybrid density functional theory defect chemistry analysis demonstrate tri-rutile zinc antimonate, ZnSb2O6, an ideal oxide identify gallium as optimal dopant yield high transparency. To validate our computational...
The recent prediction that honeycomb lattices of ${\mathrm{Co}}^{2+}$ $(3{d}^{7})$ ions could host dominant Kitaev interactions provides an exciting direction for exploration new routes to stabilizing Kitaev's quantum spin liquid in real materials. ${\mathrm{Na}}_{3}{\mathrm{Co}}_{2}{\mathrm{SbO}}_{6}$ has been singled out as a potential material candidate provided and orbital moments couple into ${J}_{\mathrm{eff}}=\frac{1}{2}$ ground state, the relative strength trigonal crystal field...
The multifaceted character of 5f electrons in actinide materials, from localized to itinerant and between, together with their complex interactions 6d other conduction electron states, has thwarted efforts for fully understanding this class compounds. While theoretical abound, direct experimental probes relevant electronic states hybridization are limited. Here we exploit the presence sizable quadrupolar dipolar contributions uranium L3-edge X-ray absorption cross section provide unique...
We investigate the low temperature structural and electronic properties of type-I clathrate Eu${}_{8}$Ga${}_{16}$Ge${}_{30}$ under pressure using x-ray powder diffraction (XRD), absorption near-edge structure (XANES), magnetic circular dichroism (XMCD) techniques. The XRD measurements reveal a transition to an amorphous phase above 18 GPa. Unlike previous reports on other compounds, no volume collapse is observed prior crystalline-amorphous which takes place when unit cell reduced 81$%$ its...
The ground-state orbital occupancy of the Ru$^{4+}$ ion in Ca$_{2-x}$La$_x$RuO$_4$ [x=0, 0.05(1), 0.07(1) and 0.12(1)] was investigated by performing X-ray absorption spectroscopy (XAS) vicinity O K edge as a function angle between incident beam surface crystals. A minimal model hybridization 2p states probed at Ru 4d orbitals used to analyze XAS data, allowing ratio hole occupancies $n_{xy}/n_{yz,zx}$ be determined doping temperature. For samples displaying low-temperature insulating...