A5089725103- Magnetic and transport properties of perovskites and related materials
- Crystallization and Solubility Studies
- Advanced Condensed Matter Physics
- X-ray Diffraction in Crystallography
- Multiferroics and related materials
- Physics of Superconductivity and Magnetism
- Magnetism in coordination complexes
- Lanthanide and Transition Metal Complexes
- Dielectric properties of ceramics
- Hydrogen Storage and Materials
- Thermal Expansion and Ionic Conductivity
- Ferroelectric and Piezoelectric Materials
- Rare-earth and actinide compounds
- Boron and Carbon Nanomaterials Research
- High-pressure geophysics and materials
- Luminescence Properties of Advanced Materials
- Electronic and Structural Properties of Oxides
- Astro and Planetary Science
- Organic and Molecular Conductors Research
- 2D Materials and Applications
- Solid-state spectroscopy and crystallography
- Topological Materials and Phenomena
- Inorganic Chemistry and Materials
- Catalysis and Oxidation Reactions
- Magnetic Properties of Alloys
Universidad Complutense de Madrid
2012-2022
Rutgers, The State University of New Jersey
2015
University of Edinburgh
2006-2013
Instituto de Ciencia de Materiales de Madrid
2003-2012
Consejo Superior de Investigaciones Científicas
2001-2012
Institut Néel
2008
University of Glasgow
2006-2008
Université Joseph Fourier
2008
Université Grenoble Alpes
2008
Centre National de la Recherche Scientifique
2008
We present a detailed analysis of the heat capacity near-perfect $S=1/2$ kagome antiferromagnet, zinc paratacamite ${\mathrm{Zn}}_{x}{\mathrm{Cu}}_{4\ensuremath{-}x}(\mathrm{OH}{)}_{6}{\mathrm{Cl}}_{2}$, as function stoichiometry $x\ensuremath{\rightarrow}1$ and for fields up to 9 T. obtain intrinsic layers by accounting weak ${\mathrm{Cu}}^{2+}/{\mathrm{Zn}}^{2+}$ exchange between Cu Zn sites, which was measured independently $x=1$ using neutron diffraction. The evolution $x=0.8\dots{}1$ is...
The synthesis, structure and magnetic properties of [CoII4CoIII3(HL)6(NO3)3(H2O)3]2+ {H3L = H2NC(CH2OH)3} are reported: the complex is an exchange-biased single molecule magnet.
The first transition-metal-only double perovskite compound, Mn(2+) 2 Fe(3+) Re(5+) O6 , with 17 unpaired d electrons displays ferrimagnetic ordering up to 520 K and a giant positive magnetoresistance of 220 % at 5 8 T. These properties result from the ferrimagnetically coupled Fe Re sublattice are affected by two-to-one magnetic-structure transition Mn when magnetic field is applied. Theoretical calculations indicate that half-metallic state can be mainly attributed spin polarization sites.
An investigation of the magnetic properties cobalt(II) citrate cubane [C(NH 2) 3] 8{Co 4(cit) 4}.4H 2O reveals that cluster is a new single-molecule magnet, with an energy barrier to reorientation magnetization, Delta E/ k B = 21 K, and tau 0 8 x 10 (-7) s. The compound displays distinct, frequency-dependent peaks in out-of-phase (chi'') component ac susceptibility magnetization versus field hysteresis loops are temperature sweep rate dependent. collapse at zero due very fast quantum tunneling (QTM).
Moderate-pressure techniques (P=2 GPa) have been used to prepare the complex LaCu3Mn4O12 perovskite. It has characterized by neutron powder diffraction, magnetic, and magnetotransport measurements. This material is ferrimagnetic below TC=361 K. The magnetoresistance (MR) enhanced with respect that of CaCu3Mn4O12 due effective electronic injection dramatically reduces bulk resistivity, thus promoting grain-boundary contribution electrical resistance. Values low-field MR close 3% at room...
[Ni4Cl4(HL)4] () {H2L=HN(CH2CH2OH)2} has S4 symmetry and crystallises in the tetragonal space group I4(1)/a. Two exchange couplings are observed between four Ni(II) centres, with J1=7.29 cm(-1) J2=-2.08 cm(-1), leading to an S=4 ground state. The Ni4 complex shows onset of frequency dependent signals out-of-phase ac susceptibility below 3 K. In single-crystal measurements carried out using a micro-SQUID, hysteresis loops 0.5 K, confirming that slow relaxation magnetisation. temperature but...
Transition-metal-only double perovskite oxides (A2BB′O6) are of great interest due to their strong and unusual magnetic interactions; only one compound, Mn2FeReO6, was reported in this category date. Herein, we report the second transition-metal-only perovskite, Mn2MnReO6, prepared at high pressure temperature. Mn2MnReO6 crystallizes a monoclinic P21/n structure, as established by synchrotron X-ray powder neutron diffraction (PND) methods, with eight-coordinated A sites rock-salt arrangement...
R2NiMnO6 (R = Tb, Ho, Er, Tm) perovskites have been prepared by soft-chemistry techniques followed high oxygen-pressure treatments; they investigated X-ray diffraction, neutron powder diffraction (NPD), and magnetic measurements. In all cases the crystal structure is defined in monoclinic P21/n space group, with an almost complete order between Ni2+ Mn4+ cations octahedral perovskite sublattice. The low temperature NPD data macroscopic measurements indicate that compounds are ferrimagnetic,...
High pressure X-ray diffraction, Raman scattering, and electrical measurements, together with theoretical calculations, which include the analysis of topological electron density electronic localization function, evidence presence an isostructural phase transition around 2 GPa, a Fermi resonance 3.5 pressure-induced decomposition SnSb2Te4 into high-pressure phases its parent binary compounds (α-Sb2Te3 SnTe) above 7 GPa. The internal polyhedral compressibility, behavior Raman-active modes,...
The reaction of M(O2CMe)2·4H2O (M = Ni, Co) with NaN3 in pyridine/MeOH under microwave irradiation and controlled pressure/temperature leads to the formation trimetallic species [M3(N3)3(O2CMe)3(py)5] 1; Co, 2) 4 min high yields. Both complexes display dominant ferromagnetic interactions high-spin ground states.
Folding under pressure: High-pressure crystallography of an Mn6 single-molecule magnet reveals dramatic changes in the intramolecular geometry magnetic core (see picture; Mn purple, O red, N blue). These structural effect properties molecule: magnitude ferromagnetic exchange between metals is decreased, and extreme pressure switches to antiferromagnetic.
Pressure-induced switching of a fast-relaxing single-molecule magnet to slow-relaxing isomer is observed for the first time by using combination high pressure single-crystal X-ray diffraction and magnetic measurements.
Abstract Above‐room‐temperature polar magnets are of interest due to their practical applications in spintronics. Here we present a strategy design high‐temperature magnetic oxides the corundum‐derived A 2 BB′O 6 family, exemplified by non‐centrosymmetric ( R 3) Ni 3 TeO ‐type Mn 2+ Fe 3+ Mo 5+ O , which shows strong ferrimagnetic ordering with T C =337 K and demonstrates structural polarization without any ions n −1)d 10 s 0 d or stereoactive lone‐pair electrons. Density functional theory...
The first combined high pressure single-crystal X-ray diffraction and magnetism study of two polymetallic clusters is presented in an attempt to correlate the observed changes structure with magnetic response without need for external ligation. At 1.5 GPa [Mn6O2(Et-sao)6(O2CPh(Me)2)2(EtOH)6] (1; Et-saoH2 = 2-hydroxyphenylpropanone)—a single molecule magnet (SMM) effective anisotropy barrier ∼86 K—and [Mn6O2(Et-sao)6(O2C-naphth)2(EtOH)4(H2O)2] 2 both undergo significant structural distortions...
Magnetic measurements and Raman spectroscopy of CoFe<sub>2</sub>O<sub>4</sub> particles 4.4 nm mean size are shown as an illustration.
CaCu2.5Mn4.5O12 perovskite has been prepared in polycrystalline form under moderate pressure conditions of 20 kbar, the presence KClO4 as oxidizing agent. This material studied by X-ray and neutron powder diffraction (NPD), magnetic, magnetotransport, thermopower measurements. The crystal structure is cubic, space group Im3̄ (No. 204), with a = 7.2279(1) Å at room temperature (RT). In ABO3 superstructure, A positions are occupied Ca2+ (Cu2.52+Mn0.53+), ordered 1:3 arrangement giving rise to...
The compounds of the title series have been prepared from citrate precursors under moderate pressure conditions (P = 2 GPa) and 1000 degrees C in presence KClO(4) as oxidizing agent. crystal structures are cubic, space group Im3 (No. 204); unit cell parameters linearly vary a 7.3272(4) A (R La) to 7.2409(1) Lu) at room temperature. neutron or synchrotron X-ray diffraction study all members reveals an interesting correlation between some structural magnetic properties. electron injection...
Pb2MReO6 (M = Co, Cr) perovskites were prepared by high pressure–high temperature method. Rietveld refinements of synchrotron powder X-ray diffraction show that the crystal structure Pb2CoReO6 is trigonal (space group R-3) with almost complete ordering Co and Re cations, while Pb2CrReO6 Pm-3m) a cubic perovskite one single site for Cr atoms. The difference between symmetry degree order was further clarified absorption spectroscopy establishes formal oxidation states in these phases as...
Selected members of the perovskite series NdNi1 − xMnxO3 (0 ≤ x 1) have been prepared by a soft chemistry technique, followed thermal treatments either under high oxygen pressure (x 0.5) or in air > 0.5). The crystal and magnetic structures studied means neutron diffraction, complemented with susceptibility measurements. For = 0.25, 0.75, structure perovskites can be defined orthorhombic Pbnm space group, Ni Mn distributed at random over octahedral sites structure. In contrast, 0.5 compound...
Multiferroic materials exhibit two or more ferroic orders and have potential applications as multifunctional in the electronics industry. A coupling of ferroelectricity ferromagnetism is hereby particularly promising. We show that synthetic melanostibite mineral Mn2 FeSbO6 (R3‾ space group) with ilmenite-type structure exhibits cation off-centering results alternating modulated displacements, thus allowing antiferroelectricity to occur. Massive magnetoelectric (MEC) magnetocapacitance effect...