A new intersecting tunnel structure in the AIMIII[PO3(OH)]2 series for AI = Ag, MIII = In : Analysis of structural relationships.

A new indium hydroxyphosphate containing silver, AgIn[PO3(OH)]2, has been synthesized using hydrothermal method. It crystallizes in the P21/c space group with the cell parameters a = 6.6400(2)Å, b=14.6269(6)Å, c=6.6616(4)A, β=95.681(5)°, V=643.82(6)Å3, Z=4. Its three-dimensional framework, built up of comer-sharing PO3(OH) tetrahedra and InO6 octahedra, presents intersecting tunnels running along and [100] directions, in which the Ag+ cations are located. The presence of hydroxyl groups has been confirmed from IR spectroscopy studies and hydrogen atoms were located from the single crystal X-ray diffraction study. The structural relationships with the other compounds of general formula AΙΜΙΙΙ[PΟ3(OH)]2 are analyz

Induced Ferromagnetism and Colossal Magnetoresistance by Ir-Doping in Pr1-xCaxMnO3

The doping of the manganese site by iridium (up to 15%) in the small A cation manganites Pr_{1-x}Ca_xMnO_3 (0.4 < x < 0.8), has been investigated as a new method to suppress charge-ordering and induce CMR effects. Ir doping leads to ferromagnetism and to insulator to metal transitions, with high transition temperatures reaching 180K and CMR ratio in 7T as large as 10^4. The efficiency with which iridium induces ferromagnetism and CMR is compared to previous results obtained with other substitutions (Ru, Rh, Ni, Cr, ...). The ionic radius of the foreign cations and their mixed-valencies are found to be the main parameters governing the ability to collapse the charge-ordered state.Comment: 9 pages, 5 figures, accepted for publication in Eur. Phys. J.

Magnetodielectric coupling and multi-blocking effect in the Ising-chain magnet Sr2Ca2CoMn2O9

We have demonstrated magnetodielectric (MD) coupling in an Ising-chain magnet Sr2Ca2CoMn2O9, via detailed investigation of ac susceptibility and dielectric constant as a function of temperature, magnetic field and frequency. Sr2Ca2CoMn2O9 consists of spin-chains, made of the regular stacking of one CoO6 trigonal prism with two MnO6 octahedra. The (Co2+ Mn4+ Mn4+) unit stabilizes a (up-down-up) spin-state along the chains which are distributed on a triangular lattice. This compound undergoes a partially disordered antiferromagnetic transition at TN ~ 28 K. The dielectric constant exhibits a clear peak at TN only in presence of an external magnetic field (above 5 kOe), evidencing the presence of MD coupling, which is further confirmed by field-dependent dielectric measurements. We argue that spatial inversion symmetry can be broken as a result of exchange-striction along each spin chain, inducing uncompensated local dipoles. At low temperatures, a dipolar relaxation phenomenon is observed, bearing strong similarities with the blocking effect typical of the spin dynamics in this compound. Such a spin-dipole relationship is referred to as a multi-blocking effect, in relation with the concept of magnetodielectric multiglass previously introduced for related materials.Comment: Multiferroicity, Magnetoelectric coupling, Complex exchange interaction, spin-chain oxid

Introducing Barium in Transition Metal Oxide Frameworks Impact upon Superconductivity, Magnetism, Multiferroism and Oxygen Diffusion and Storage

International audienceThe role of barium in the structural chemistry of some transition metal oxides of the series "Cu, Mn, Fe, Co" is reviewed, based on its size effect and its particular chemical bonding. Its impact upon various properties, superconductivity, magnetism, multiferroism, oxygen storage is emphasized

Recherche de compositions à base de Ba(Zn1/3X2/3)O3(X=Ta ou Nb) pour la conception de condensateurs multicouches à armatures en métaux non-nobles

CAEN-BU Sciences et STAPS (141182103) / SudocSudocFranceF

Manganites à base de bismuth (étude du système (Bi, Sr, Ca)MnO3)

CAEN-BU Sciences et STAPS (141182103) / SudocSudocFranceF