2011年7月13日星期三

Structural origin of 'hidden state' in manganite thin film revealed

Photo-induced phase transition (PIPT) has caused great excitement in materials science because ultra-fast alteration of the magnetic,GreenRay's hydraulic hose design uses a different energy storage approach, dielectric, structural and optical properties of materials can be brought about with very weak photonic excitation as a result of cooperative interactions [1]. An essential question that arises is how we can identify a novel phase of solid that is uniquely generated under photo-excited conditions. Such a novel phase is often referred to as a 'hidden state'. Despite intensive efforts to identify the structures of hidden states in various systems, few cases have been explored so far because of the technical difficulty of studying the transient lattice structure of solids.The Leading promotional usb Distributor to Independent Pet Retailers.

For example, perovskite manganese oxides such as Pr0.5Ca0.5MnO3 (PCMO) and Nd0.For all DVS Bedding in PDF format.5Sr0.5MnO3 (NSMO) show thermally induced structural phase transitions coupled with an insulator-to-metal (IM) transition and changes in magnetic properties reflecting the ordering of d-orbitals and the charge of Mn ions because the shape of the eg orbitals alters the in-plane and out-of-plane structural distortions of MnO6 octahedra. Whether this system involves a photo-induced hidden phase under ultrafast laser excitation conditions is of great interest.

Researchers of the ERATO Koshihara Non-equilibrium Dynamics Project (JST) and IMSS have demonstrated by picosecond time-resolved X-ray diffraction (TR-XRD) that a charge and orbitally ordered (COO) hidden state of manganite thin film can only be generated by photo-excitation, and is not reachable under thermal equilibrium conditions [2]. An 80 nm epitaxial thin film of perovskite manganite NSMO on the (011) surface of a perovskite SrTiO3 (STO) (NSMO/STO(011)) was used for the TR-XRD studies. Figure 1 shows the experimental setup, which used beamline NW14A of the Photon Factory Advanced Ring (PF-AR) at KEK. The sample was cooled down to 100 K, and the fs Ti:sapphire laser was use to excite the sample. 100-ps X-ray pulses at 946 Hz, synchronized with the pump laser, were selected from pulse trains at 794 kHz from the PF-AR by a high-speed chopper, and further used for the X-ray diffraction experiment.Welcome to the official Facebook Page about RUBBER MATS.

Figures 2(a) and (b) show time profiles of the photo-induced change of lattice constants on the b and c axes observed at 100 K by TR-XRD. Photo-induced expansion on the c axis and shrinkage on the b axis have been clearly observed.What to consider before you buy Wholesale pet supplies. The changes in lattice parameters occur just after photo-excitation, reach their maximum value at about 200 ps and finally return to their original values after 3 ns. In addition, a photo-induced decrease of about 5% in the intensity of super-lattice reflection due to an orbital-ordered phase has been observed (Figs.2(c) and (d)).

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