We have experimentally demonstrated thermal rectification as bulk effect. According to a theoretical design of a thermal rectifier, we have prepared an oxide thermal rectifier made of two cobalt oxides with different thermal conductivities, and have made an experimental system to detect the thermal rectification. The rectifying coefficient of the device is found to be 1.43, which is in good agreement with the numerical calculation.Comment: 4 pages, 4 figures, Appl. Phys. Lett. (in press

We studied how the addition of surfactants alters the drying and film formation processes of polymer solution droplets with contact lines strongly fixed by bank structures. We found that even if the amount of surfactant is quite small, it drastically changes the final profile of the polymer film from a ringlike profile to a flat profile. This property is observed commonly, irrespective of the polymer concentration, droplet volume, and type of solvent. We conjecture that the inhomogeneous distribution of the surfactant caused by the outward capillary flow induces the Marangoni flow directed toward the center of the droplet, which suppresses the outward flow. The present phenomenon implies an effective method for controlling the profile of the polymer film in inkjet printing technologies.

We have measured susceptibility, specific heat, resistivity, and thermopower of CaCu3Ti4−xRuxO12 and CaCu3−yMnyRu4O12, and have found that CaCu3Ru4O12 can be regarded as a heavy-fermion oxide in d-electron systems. The Kondo temperature is near 200 K, and the susceptibility (1.4×10 −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 CaCu3Ti4−xRuxO12, which can be regarded as a transition from magnetic insulator to heavy-fermion metal.

We have measured magnetic susceptibility and resistivity of Sr1−xYxCoO 3−δ (x = 0. 1, 0.15, 0.2, 0.215, 0.225, 0.25, 0.3, and 0.4), and found that Sr1−xYxCoO 3−δ is a room temperature ferromagnet with a Curie temperature of 335 K in a narrow compositional range of 0.2 ≤ x ≤ 0.25. This is the highest transition temperature among perovskite Co oxides. The saturation magnetization for x = 0.225 is 0.25 µB/Co at 10 K, which implies that the observed ferromagnetism is a bulk effect. We attribute this ferromagnetism to a peculiar Sr/Y ordering.