822 research outputs found
High temperature behavior of Sr-doped layered cobaltites Y(Ba1-xSrx)Co2O5.5: phase stability and structural properties
In this article we present a neutron diffraction in-situ study of the thermal
evolution and high-temperature structure of layered cobaltites Y(Ba, Sr)Co2
O5+{\delta}. Neutron thermodiffractograms and magnetic susceptibility
measurements are reported in the temperature range 20 K <= T <= 570 K, as well
as high resolution neutron diffraction experiments at selected temperatures.
Starting from the as-synthesized samples with {\delta} ~ 0.5, we show that the
room temperature phases remain stable up to 550 K, where they start loosing
oxygen and transform to a vacancy-disordered "112" structure with tetragonal
symmetry. Our results also show how the so-called "122" structure can be
stabilized at high temperature (around 450 K) in a sample in which the addition
of Sr at the Ba site had suppressed its formation. In addition, we present the
structural and magnetic properties of the resulting samples with a new oxygen
content {\delta} ~ 0.25 in the temperature range 20 K <= T <= 300 K
Switching of the Chiral Magnetic Domains in the Hybrid Molecular/Inorganic Multiferroic (ND4)2[FeCl5(D2O)]
(ND4)2[FeCl5(D2O)] represents a promising example of the hybrid molecular/inorganic approach to create materials with strong magneto-electric coupling. Neutron spherical polarimetry, which is directly sensitive to the absolute magnetic configuration and domain population, has been used in this work to unambiguously prove the multiferroicity of this material. We demonstrate that the application of an electric field upon cooling results in the stabilization of a single-cycloidal magnetic domain below 6.9 K, while poling in the opposite electric field direction produces the full population of the domain with opposite magnetic chirality. We prove the complete switchability of the magnetic domains at low temperature by the applied electric field, which constitutes a direct proof of the strong magnetoelectric coupling. Additionally, we refine the magnetic structure of the ordered ground state, deducing the underlying magnetic space group consistent with the direction of the ferroelectric polarization, and we provide evidence of a collinear amplitude-modulated state with magnetic moments along the a-axis in the temperature region between 6.9 and 7.2 K
Colloidal processing of Al2O3-doped zirconia ceramics with CaO–P2O5–SiO2 glass as additive
Well dispersed concentrated aqueous suspensions of Al2O3-doped Y-TZP (AY-TZP), AY-TZP with 5.4 vol% of CaO-P2O5-SiO2 (CaPSi) glass (AY-TZP5) and 10.5 vol% CaPSi glass (AY-TZP10), with ammonium polyacrylate (NH4PA) dispersant were prepared to produce slip cast compacts. The rheological properties of 35 and 40 vol% slips were studied. The densification, microstructure as well as hardness and fracture toughness were investigated as a function of CaPSi glass content at 1300-1500 oC. The optimum NH4PA concentration of 35 vol% AY-TZP5 and AY-TZP10 slips at pH ~9 was found to be about 43 and 67 % greater than that of AY-TZP slips, this behaviour was related to the greater amounts of Ca2+ ions leached out from the CaPSi glass surface. The viscosity of stabilized 40 vol% slips with NH4PA attained a minimum value at 5.4 vol% CaPSi glass addition, and resulted in a more dense packing of cast samples. AY-TZP5 can be sintered at a lower temperature (1300 oC) compared to that of AY-TZP. AY-TZP5 exhibited a fine microstructure of tetragonal ZrO2 (grain sizes below 0.3 m), and ZrSiO4 - Ca2P2O7 particles homogeneously distributed within the zirconia matrix. Its presented similar fracture toughness and a slightly lower hardness compared to those of AY-TZP.Fil: Soubelet, Clara Gabriela. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; ArgentinaFil: Albano, Maria Patricia. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; Argentin
Long-range order and low-energy magnetic excitations in CeRu2Al10
The nature of the unconventional ordered phase occurring in CeRu2Al10 below
T0 = 27 K was investigated by neutron scattering. Powder diffraction patterns
show clear superstructure peaks corresponding to forbidden (h + k)-odd
reflections of the Cmcm space group. Inelastic neutron scattering experiments
further reveal a pronounced magnetic excitation developing in the ordered phase
at an energy of 8 meV.Comment: 5 pages; 4 figure
Multiferroic behavior in the new double-perovskite LuMnCoO
We present a new member of the multiferroic oxides, LuMnCoO, which we
have investigated using X-ray diffraction, neutron diffraction, specific heat,
magnetization, electric polarization, and dielectric constant measurements.
This material possesses an electric polarization strongly coupled to a net
magnetization below 35 K, despite the antiferromagnetic ordering of the Mn and Co spins in an configuration along the c-direction. We discuss the magnetic order
in terms of a condensation of domain boundaries between and
ferromagnetic domains, with each domain boundary
producing a net electric polarization due to spatial inversion symmetry
breaking. In an applied magnetic field the domain boundaries slide, controlling
the size of the net magnetization, electric polarization, and magnetoelectric
coupling
Aplicación de la termografía en el estudio de la ubre de los grandes rumiantes y en sus posibles complicaciones patológicas
Se ha estudiado la aplicación de la termografía en la ubre sana y con mamitis, en ganado vacuno Frisón y de carne ecológica mestizo. Se han valorado distintos factores que influyen en la aplicación de esta técnica, tanto del animal (pelo, pliegue inguinal) como externos a éste (suciedad, ambiente). Se ha establecido la relación entre la temperatura superficial de la ubre y sus patologías, centrando el estudio en mamitis.The application of the thermography has been studied in healthy and mastitic udder, both in dairy Holstein and organic beef mixed-breed cattle. Different factors that may influence the application of this technology have been evaluated, both animal (hair, inguinal fold) and external factors (dirt, environment). The aim of this study was to establish a relation between the superficial temperature of the udder and its pathologies, focusing he study on mastitis
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