A5013870602- Advanced Condensed Matter Physics
- Crystal Structures and Properties
- Crystallization and Solubility Studies
- X-ray Diffraction in Crystallography
- Magnetic and transport properties of perovskites and related materials
- High-pressure geophysics and materials
- Physics of Superconductivity and Magnetism
- Geological and Geochemical Analysis
- Nuclear materials and radiation effects
- Iron-based superconductors research
- 2D Materials and Applications
- Multiferroics and related materials
- Quantum and electron transport phenomena
- Catalytic Processes in Materials Science
- Chalcogenide Semiconductor Thin Films
- Ionosphere and magnetosphere dynamics
- Organic and Molecular Conductors Research
- Solar and Space Plasma Dynamics
- Electronic and Structural Properties of Oxides
- Theoretical and Computational Physics
- GNSS positioning and interference
- Heusler alloys: electronic and magnetic properties
- Thermal and Kinetic Analysis
- Intermetallics and Advanced Alloy Properties
- Astro and Planetary Science
Universidade Federal Fluminense
2008-2024
Centro Brasileiro de Pesquisas Físicas
2014-2021
Institut Néel
2013-2021
Université Grenoble Alpes
2013-2021
Centre National de la Recherche Scientifique
2013-2021
Université Joseph Fourier
2013-2014
National Institute for Space Research
2003
We have synthesized for the first time metastable compound 1T-CrTe2. done its complete structural characterization and measured magnetization, specific heat electrical resistivity between 4 330 K. also performed detailed band structure calculations. found that it crystallizes in CdI2 type resistance follows a metallic behaviour below room temperature. Its magnetization curves show has transition to ferromagnetic state at TC = 310 K, with magnetic moments ordered parallel basal plane. From...
We present measurements of the superconducting and charge density wave critical temperatures (Tc TCDW) as a function pressure in transition metal dichalchogenides 2H-TaSe2 2H-TaS2. Resistance susceptibility show that Tc increases from below 1 K up to 8.5 at 9.5 GPa 2H-TaS2 8.2 23 2H-TaSe2. observe kink dependence TCDW about 4 we attribute lock-in incommensurate CDW commensurate CDW. Above this pressure, slowly decreases coexisting with superconductivity within our full range.
We present an extensive study of the structural, magnetic, and thermodynamic properties oxyborate ${\text{Co}}_{3}{\text{O}}_{2}{\text{BO}}_{3}$. This is carried out through x-ray diffraction, static dynamic magnetic susceptibilities, specific heat experiments in single crystals a large temperature range. The structure ${\text{Co}}_{3}{\text{O}}_{2}{\text{BO}}_{3}$ composed subunits form three-leg ladders where Co ions with mixed valency are located. this ludwigite determined by competition...
We present an extensive study of the structural, magnetic, and thermodynamic properties two heterometallic oxyborates: ${\text{Co}}_{2}{\text{FeO}}_{2}{\text{BO}}_{3}$ ${\text{Ni}}_{2}{\text{FeO}}_{2}{\text{BO}}_{3}$. This has been carried out through x-ray diffraction at room temperature (RT) 150 K, dc ac magnetic susceptibilities, specific-heat experiments in single crystals above 2 K. The these iron ludwigites are discussed comparison with those other known homometallic ludwigites:...
There are two known ludwigites containing a single transition metal element, ${\text{Fe}}_{3}{\text{O}}_{2}{\text{BO}}_{3}$ and ${\text{Co}}_{3}{\text{O}}_{2}{\text{BO}}_{3}$. The structure of these materials has low-dimensional units in the form three-legged ladders (3LL) that confer to each them unique magnetic electronic properties. presents staggered charge density wave (CDW) near room temperature transitions. It remained mystery why other compound...
We have studied the effect of substitution Cr in metastable $1T$-CrSe${}_{2}$ by Ti and V on its structural magnetic properties. The transitions observed between 165--180 K pure material are stomped doping. compound has a magnetization corresponding to an antiferromagnetic (AF) ground state. On substitution, we observe increase lattice constants gradual passage towards ferromagnetic state, while replacement maintains AF order up our highest doping, ${x}_{\text{V}}=0.5$. With experimental...
We present an extensive study of the oxyborate material ${\text{Co}}_{5}\text{Ti}{({\text{O}}_{2}{\text{BO}}_{3})}_{2}$ using x-ray, magnetic, and thermodynamic measurements. This belongs to a family oxyborates known as ludwigites which presents low-dimensional subunits in form three leg ladders its structure. Differently from previously investigated does not show long-range magnetic order although it goes into spin-glass state at low temperatures. The different techniques employed this...
The ludwigite ${\text{Co}}_{5}\text{Sn}({\mathrm{O}}_{2}{\text{BO}}_{3}{)}_{2}$ was studied using x-ray diffraction, M\"ossbauer spectroscopy, and magnetic thermodynamic measurements. This material belongs to a family of oxyborates which presents low-dimensional subunits in the form three-leg ladders its structure. confer these materials strong anisotropy their exchange interactions that provide ludwigites several interesting properties, from partial ordering spin-glass states. Despite being...
The mixed-valent homometallic ludwigite $({\mathrm{Co}}_{2}^{2+}{\mathrm{Co}}^{3+}){\mathrm{O}}_{2}{\mathrm{BO}}_{3}$ is investigated above the ferrimagnetic ordering temperature ${T}_{C}=43\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ through structural, thermal, magnetic, electric, and spectroscopic probes. X-ray absorption at Co ${L}_{2,3}$ edges consistent with coexistence of ${\mathrm{Co}}^{2+}$ ${\mathrm{Co}}^{3+}$ ions, as expected by sample stoichiometry. Magnetic susceptibility shows a...
This paper presents an extensive study of the structural, magnetic, and thermodynamic properties heterometallic ludwigite ${\mathrm{Co}}_{4.76}{\mathrm{Al}}_{1.24}{({\mathrm{O}}_{2}{\mathrm{BO}}_{3})}_{2}$. material orders ferrimagnetically at 57 K. Despite fact that, in ${\mathrm{Co}}_{4.76}{\mathrm{Al}}_{1.24}{({\mathrm{O}}_{2}{\mathrm{BO}}_{3})}_{2}$, one quarter Co ions parent compound ${\mathrm{Co}}_{3}{\mathrm{O}}_{2}{\mathrm{BO}}_{3}$ is replaced by nonmagnetic ${\mathrm{Al}}^{3+}$...
Charge ordering is prone to occur in crystalline materials with mixed-valence ions. It presumably accompanied by a structural phase transition, possible exceptions compounds that already present more than one inequivalent site for the ions charge-disordered phase. In this work, we investigate representative case of homometallic Co ludwigite ${\mathrm{Co}}_{2}^{2+}{\mathrm{Co}}^{3+}{\mathrm{O}}_{2}{\mathrm{BO}}_{3}$ ($Pbam$ space group) four distinct crystallographic sites [$M1$--$M4$]...
Spin-state ordering - a periodic pattern of ions with different spin-state configurations along crystal lattice is rare phenomenon, and its possible interrelation other electronic degrees freedom remains little explored. Here we perform structural investigation the mixed-valence Co homometallic ludwigite Co$_2^{2+}$Co$^{3+}$O$_2$BO$_3$. A superstructure consistent long-range Co$^{3+}$ observed between $T_{4}=580$ K $T_{3}=510$ K. Intermediate states mesoscopic correlations are detected below...
A large number of oxyborates studied up to now exhibit warwickite- or ludwigite-type structure with one-dimensional subunits (ladders ribbons). The crystalline anisotropy strongly affects the physical properties these systems. In this paper we present an extensive structural, magnetic, and thermodynamic study oxyborate ${\text{Co}}_{5.52}{\text{Sb}}_{0.48}{({\text{O}}_{2}{\text{BO}}_{3})}_{2}$ a hulsite-type structure. Differently from previously oxyborates, material is characterized by...
X-ray diffraction, magnetization, ac susceptibility, and specific heat have been measured on high-quality single crystals of ${\mathrm{Co}}_{3}{\mathrm{Mn}}_{3}{({\mathrm{O}}_{2}{\mathrm{BO}}_{3})}_{2}$ ludwigite. Different from previously studied ludwigites, this compound is characterized by the existence two low-dimensional subunits each containing a unique ion. The subsystem formed ions at sites 3-1-3, known as three-legged ladder (3LL), contains only divalent Co ions, while 3LL 4-2-4...
We have studied the resistance of $1T$-CrSe${}_{2}$, as Cr atoms are substituted by V or Ti. The replacement leads to a logarithmic increase in temperature is lowered, proportional concentration. While this behavior consistent with Kondo effect, weak dependence magnetic field and fact that system has antiferromagnetic order, rule out effect due spin degeneracy. In contrast case V, Ti substitution does not term while application pressure destroys it. Calculations electronic structure within...
The crystal structure and the magnetic properties of ${\mathrm{Co}}_{2.5}{\mathrm{Cr}}_{0.5}{\mathrm{BO}}_{5}$ ludwigite have been investigated by x-ray diffraction, magnetization, specific heat experiments. Cr ions mainly occupy sites 4 lattice, substituting approximately half ${\mathrm{Co}}^{3+}$. It changes interatomic distances favors a high spin state for remaining ${\mathrm{Co}}^{3+}$ ions. Doping homometallic ${\mathrm{Co}}_{3}{\mathrm{BO}}_{5}$ with drastically increases transition...
We present the results of a thorough study specific heat and magnetocaloric properties ludwigite crystal Cu2MnBO5 over temperature range 60 - 350 K in magnetic fields up to 18 kOe. It is found that at temperatures below Curie (92 K), capacity possesses linear temperature-dependent behavior, which associated with predominance two-dimensional antiferromagnetic interactions magnons. The independence observed 95 160 K, can be attributed excitation Wigner glass phase. effect (i.e. adiabatic...
We study the $\mathrm{C}{\mathrm{r}}_{1\ensuremath{-}x}\mathrm{R}{\mathrm{e}}_{x}$ phase diagram finding that its transition temperature towards an antiferromagnetic order ${T}_{N}$ follows a quantum ${[({x}_{c}\ensuremath{-}x)/{x}_{c}]}^{\ensuremath{\psi}}$ law, with $\ensuremath{\psi}=1/2$, from critical point (QCP) at ${x}_{c}=0.25$ up to ${T}_{N}\ensuremath{\approx}600\phantom{\rule{0.28em}{0ex}}\mathrm{K}$. compare this system others in understand why elemental material is affected by...
We determine the pressure phase diagram of 1111 compounds CaFeAsF and SrFeAsF, up to 20 GPa down 4 K by electrical resistivity measurements change structure 40 at room temperature. The antiferromagnetic transition temperature, as determined derivative peak, shows a minimum ~5 (10 GPa) for Ca (Sr) compound. For CaFeAsF, superconductivity appears this minimum, coincident with development previously reported monoclinic phase. where orthorhombic were coexist, exists above P≥1 GPa. Both diagrams...
This paper presents an extensive study of the structural, magnetic, and thermodynamic properties hulsite ${\mathrm{Ni}}_{5.15}{\mathrm{Sn}}_{0.85}{({\mathrm{O}}_{2}{\mathrm{BO}}_{3})}_{2}$. The crystal structure has two planar substructures formed by Ni Sn atoms: one with rectangular configuration other a triangular arrangement. These are linked boron ions in another site closer to arrangement, resulting quasi-two-dimensional character. Thus, this system literally adds new dimension...
The magnetic properties of site-disordered ${\mathrm{Ni}}_{5}\mathrm{Sn}{({\mathrm{O}}_{2}{\mathrm{BO}}_{3})}_{2}$ ludwigite have carefully been studied using local probes and bulk experimental methods in temperatures down to 1.6 K fields up 9 T. Our results clearly shown the role effect order/disorder site occupancy these complex compounds with spin moments $S=1$. Different from most ludwigites, has three transitions at 80, 50, 5 K. Local ($^{119}\mathrm{Sn}$ M\"ossbauer muon spectroscopy)...