A novel heavy-fermion state in CaCu_3Ru_4O12

We have measured susceptibility, specific heat, resistivity, and thermopower of CaCu$_3$Ti$_{4-x}$Ru$_x$O$_{12}$ and CaCu$_{3-y}$Mn$_y$Ru$_4$O$_{12}$, and have found that CaCu$_3$Ru$_4$O$_{12}$ can be regarded as a heavy-fermion oxide in d-electron systems. The Kondo temperature is near 200 K, and the susceptibility (1.4$\times10^{-3}$ emu/Cu mol) and the electron specific heat coefficient (28 mJ/Cu molK$^2$) are moderately enhanced. The resistivity is proportional to $T^2$ at low temperatures, and satisfies the Kadowaki-Woods relation. The heavy-fermion state comes from the interaction between the localized moment of Cu 3d and the conduction electron of Ru 4d. An insulator-metal transition occurs between $x=1.5$ and 4 in CaCu$_3$Ti$_{4-x}$Ru$_x$O$_{12}$, which can be regarded as a transition from magnetic insulator to heavy-fermion metal.Comment: 4 pages, 5 figures, submitted to J. Phys. Soc. Jp

Agricultural climate change mitigation : Carbon calculators as a guide for decision making

This is an Accepted Manuscript of an article published by Taylor & Francis Group in International Journal of Agricultural Sustainability on 9 November 2017, available online: https://doi.org/10.1080/14735903.2017.1398628. Under embargo. Embargo end date: 9 November 2018.The dairy industry is receiving considerable attention in relation to both its significant greenhouse gas (GHG) emissions, and it’s potential for reducing those emissions, contributing towards meeting national targets and driving the industry towards sustainable intensification. However, the extent to which improvements can be made is dependent on the decision making processes of individual producers, so there has been a proliferation of carbon accounting tools seeking to influence those processes. This paper evaluates the suitability of such tools for driving environmental change by influencing on-farm management decisions. Seven tools suitable for the European dairy industry were identified, their characteristics evaluated, and used to process data relating to six scenario farms, emulating process undertaken in real farm management situations. As a result of the range of approaches taken by the tools, there was limited agreement between them as to GHG emissions magnitude, and no consistent pattern as to which tools resulted in the highest/lowest results. Despite this it is argued, that as there was agreement as to the farm activities responsible for the greatest emissions, the more complex tools were still capable of performing a ‘decision support’ role, and guiding management decisions, whilst others could merely focus attention on key issues.Peer reviewe

Heavy-Mass Behavior of Ordered Perovskites ACu3Ru4O12 (A = Na, Ca, La)

We synthesized ACu3Ru4O12 (A = Na, Na0.5Ca0.5, Ca, Ca0.5La0.5, La) and measured their DC magnetization, AC susceptibility, specific heat, and resistivity, in order to investigate the effects of the hetero-valent substitution. A broad peak in the DC magnetization around 200 K was observed only in CaCu3Ru4O12, suggesting the Kondo effect due to localized Cu2+ ions. However, the electronic specific heat coefficients exhibit large values not only for CaCu3Ru4O12 but also for all the other samples. Moreover, the Wilson ratio and the Kadowaki-Woods ratio of our samples are all similar to the values of other heavy-fermion compounds. These results question the Kondo effect as the dominant origin of the mass enhancement, and rather indicate the importance of correlations among itinerant Ru electrons.Comment: 6 pages, 6 figures, to be published in J. Phys. Soc. Jp

Correlations of structural, magnetic, and dielectric properties of undoped and doped CaCu3Ti4O12

The present work reports synthesis, as well as a detailed and careful characterization of structural, magnetic, and dielectric properties of differently tempered undoped and doped CaCu3Ti4O12 (CCTO) ceramics. For this purpose, neutron and x-ray powder diffraction, SQUID measurements, and dielectric spectroscopy have been performed. Mn-, Fe-, and Ni-doped CCTO ceramics were investigated in great detail to document the influence of low-level doping with 3d metals on the antiferromagnetic structure and dielectric properties. In the light of possible magnetoelectric coupling in these doped ceramics, the dielectric measurements were also carried out in external magnetic fields up to 7 T, showing a minor but significant dependence of the dielectric constant on the applied magnetic field. Undoped CCTO is well-known for its colossal dielectric constant in a broad frequency and temperature range. With the present extended characterization of doped as well as undoped CCTO, we want to address the question why doping with only 1% Mn or 0.5% Fe decreases the room-temperature dielectric constant of CCTO by a factor of ~100 with a concomitant reduction of the conductivity, whereas 0.5% Ni doping changes the dielectric properties only slightly. In addition, diffraction experiments and magnetic investigations were undertaken to check for possible correlations of the magnitude of the colossal dielectric constants with structural details or with magnetic properties like the magnetic ordering, the Curie-Weiss temperatures, or the paramagnetic moment. It is revealed, that while the magnetic ordering temperature and the effective moment of all investigated CCTO ceramics are rather similar, there is a dramatic influence of doping and tempering time on the Curie-Weiss constant.Comment: 10 pages, 11 figure

Deposition conditions for the growth of textured ZnO thin films by aerosol CVD process

The crystalline orientation of ZnO thin films deposited by an aerosol CVD process is studied with regard to the experimental conditions. The quality of the C-axis oriented growth depended on the substrate temperature, on the deposition rate and also on the hygrometric degree of the carrier gas. The quality of the gold sublayer influenced also the quality of the ZnO textured growth. Under a dry gas mixture N2-O2 at 495°C and with a deposition rate of 35Å/mn, the texture ratio was less than -3.5 and the misorientation σ002 was less than 1.6°

Elaboration par le procédé pyrosol de couches minces texturées de ZnO pour la réalisation de microcapteurs

The crystalline orientation of ZnO thin films deposited by an aerosol CVD process is studied with regard to the experimental conditions. The quality of the $C$-axis oriented growth depended on the substrate temperature, on the deposition rate and also on the hygrometric degree of the carrier gas. The quality of the gold sublayer influenced also the quality of the ZnO textured growth. Under a dry gas mixture N$_2$-O$_2$ at 495 $^{\circ}$C and with a deposition rate of 35 Å/mn, the texture ratio was less than -3.5 and the misorientation of the 002 line was less than 1.6$^{\circ}$.L'orientation cristalline de couches minces de ZnO élaborées par le procédé pyrosol est étudiée en fonction des conditions de dépôt. La qualité de la texture selon l'axe $C$ dépend de la température du substrat, de la vitesse de dépôt, du degré d'hygrométrie du gaz vecteur et également de la qualité de la sous-couche chrome/or. Pour des dépôts réalisés avec un mélange pur et sec d'azote et d'oxygène à 495 $^{\circ}$C et pour une vitesse de dépôt de 35 Å/mn, le rapport de texture est inférieur à -3,5 et la désorientation de la raie 002 est inférieure à 1,6$^{\circ}$

MAGNETIC BEHAVIOUR AND PHASE TRANSITION IN [ThCu3] (Mn4)O12

Le composé [ThCu3] (Mn4)o12 appartient à la série des oxydes [AC3] (B4)O12 de structure pérovskite dans lesquels les sites [A] icosaédriques sont occupés par les cations Th4+, les sites [C] plans-carrés par les cations Cu2+ et les sites (B) octaédriques par les cations Mn3+ et Mn4+ en proportions égales. Diverses mesures indiquent un comportement ferrimagnétique avec une température d'ordre TN = 430 K, une aimantation spontanée à 4,2 K de 9 µB/unité de formule et une transition à Tt = 180 K. La structure ferrimagnétique, déduite des expériences de diffraction neutronique est en accord avec les valeurs des interactions magnétiques tirées des mesures d'aimantation et de susceptibilité. La transition Tt a été étudiée par des mesures d'aimantation et de diffraction des rayons X. Elle est caractérisée par une variation thermique anormale du paramètre de maille et du moment magnétique, sans changement de la symétrie cristallographique et magnétique.The compound [ThCu3] (Mn4)O12 belongs to the series of [AC3] (B4) O12 perovskite-like oxides in which the icosahedral sites [A] are occupied by the Th4+ cations, the square planar sites [C] by the Cu2+ cations, and the octahedral sites (B) by the Mn3+ and Mn4+ cations in equal proportion. Previous measurements indicated a ferrimagnetic behavior with an ordering temperature TN= 430 K, a spontaneous magnetization of 9µB/formula unit at 4.2 K and a magnetic transition at Tt = 180 K. The ferrimagnetic structure, as determined from powder neutron diffraction data, is consistent with the values of magnetic interactions that can be estimated from magnetization and susceptibility measurements. The low temperature transition has been studied by magnetization measurements and X-Rays techniques. It seems to be of second order with anomalies in the cubic cell parameter and of the magnetic moments. No changes in cristallographic symmetry and magnetic structure are observed