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Pressure effects on the magnetic transition temperature in ordered double perovskites

Physical Review B 2008年第18期78卷 184416-184416页

作者： D. Di Castro P. Dore R. Khasanov H. Keller P. Mahadevan Sugata Ray D. D. Sarma P. Postorino CNR-INFM Coherentia and Department of Mechanical Engineering University of Rome “Tor Vergata” Via del Politecnico 1 I-00133 Rome Italy CNR-INFM Coherentia and Dipartimento di Fisica Università di Roma “La Sapienza” P.le A. Moro 2 I-00185 Rome Italy Physik-Institut der Universität Zürich Winterthurerstrasse 190 CH-8057 Zürich Switzerland Laboratory for Muon Spin Spectroscopy Paul Scherrer Institut CH-5232 Villigen PSI Switzerland S.N. Bose National Center for Basic Sciences JD Block Sector III Kolkata 700098 India Solid State and Structural Chemistry Unit Indian Institute of Science Bangalore 560012 India Department of Materials Science Indian Association for the Cultivation of Science Kolkata 700032 India Centre for Advanced Materials Indian Association for the Cultivation of Science Kolkata 700032 India

A study of the pressure effect on the Curie temperature in polycrystalline ordered double perovskites was carried out by measuring the temperature dependence of the magnetization in isoelectronic Sr2FeMoO6, Ba2FeMoO6, and Ca2FeMoO6, and in W-substituted Sr2FeMo1−xWxO6 with x=0.70. Pressure up to approximately 10 kbar induces an increase in the Curie temperature in all the samples with different rate: dTc/dp results to be 1.7(2) K/kbar for Ba2FeMoO6, 0.60(8) K/kbar for Sr2FeMoO6, 0.25(8) K/kbar for Ca2FeMoO6, and 0.7(1) K/kbar for the W-substituted sample. The results are interpreted in terms of the different lattice structure and cell volume of the investigated systems. A manganitelike model was only partially successful in explaining the observed pressure behavior, thus, pointing out the different nature of the magnetic interaction in doped manganites and in ordered double perovskites.

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Electron correlation effects in Co nanoscale islands on a nitrogen-covered Cu(001) surface

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Physical Review B 2008年第23期77卷 235436-235436页

作者： Kan Nakatsuji Yoshihide Yoshimoto Daiichiro Sekiba Shunsuke Doi Takushi Iimori Kazuma Yagyu Yasumasa Takagi Shin-ya Ohno Hideharu Miyaoka Masamichi Yamada Fumio Komori Kenta Amemiya Daiju Matsumura Toshiaki Ohta Institute for Solid State Physics University of Tokyo Kashiwashi Chiba 277-8581 5-1-5 Kashiwanoha Japan Department of Chemistry Graduate School of Science University of Tokyo Bunkyo-ku Tokyo 113-0033 7-3-1 Hongo Japan Tandem Accelerator Complex Research Facility Center for Science and Technology University of Tsukuba Tsukuba Ibaraki 305-8577 Japan Institute for Molecular Science Okazaki Aichi 444-8585 Japan Faculty of Engineering Yokohama National University Tokiwadai Hodogaya-ku Yokohama Kanagawa 240-8501 Japan Institute of Materials Structure Science High Energy Accelerator Research Organization (KEK) Oho Tsukuba Ibaraki 305-0801 Japan Kansai Photon Science Institute Japan Atomic Energy Agency Sayo Hyogo 679-5148 Japan High Energy Accelerator Research Organization SR Center Ritsumeikan University Noji-Higashi Kusatsu Shiga 525-8577 Japan

The electronic states of cobalt nanoislands on a nitrogen-saturated Cu(001) c(2×2)-N surface have been investigated by means of x-ray absorption spectroscopy. In the case of low coverages, when the surface is covered by small Co islands, a shoulder structure in the Co L-edge absorption spectrum is observable at an energy about 3 eV higher than the absorption edge. By considering the unoccupied Co 3d state calculated by first-principles method, x-ray photoelectron spectra and the multiple scattering during the absorption process, the shoulder is attributed to the correlation among 3d electrons. The satellite intensity decreases with the increase in the Co island size. The perimeter Co atoms of the island are assigned as the origins of the correlation satellite by comparing its intensity with the morphology of the islands observed using scanning tunneling microscopy. The polarization dependent satellite intensity suggests that the electron correlation in the in-plane 3d orbital of the perimeter atoms is larger than that in the out-of-plane one.

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Growth of TiO_2 Nanorods by Sol-gel Template Process

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Journal of materials science & Technology 2007年第5期23卷 611-613页

作者： A.Sadeghzadeh Attar Sh.Mirdamadi F.Hajiesmaeilbaigi M.Sasani Ghamsari Department of Metallurgy and Materials Engineering Iran University of Science and TechnologyTehranIran Solid State Laser Research Group Laser Research Center11365-8486TehranIran

In this work, TiO2 nanorods with uniform diameter of about 100 nm and a length of several micrometers were successfully prepared by the sol-gel template method. Also the influence of molar ratios of precursor on the morphology and structure of TiO2 nanorods has been investigated. The prepared samples were characterized by Fourier transform infrared spectroscopy （FTIR）, X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The XRD results indicated that the TiO2 nanorods were crystallized in the anatase and rutile phases, after annealing to 400-700℃ up to 2 h.

关键词： TiO2 nanorods Sol-gel process Template-based growth

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1.54 μm monolithically integrated GaSb quantum well laser diode on silicon operating at 77K

1.54 μm monolithically integrated GaSb quantum well laser d...

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International Nano-Optoelectronic Workshop, iNOW

作者： Huffaker, D.L. Balakrishnan, G. Jallipalli, A. Kutty, M.N. Tatebayashi, J. Huang, S.H. Dawson, L.R. Mi, Z. Bhattacharya, P. Center for High Technology Materials University of New Mexico Albuquerque NM 87106 United States Solid-State Electronics Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI 48109-2122 United States

We present a GaSb quantum well laser diode grown monolithically on a Si(100)-5 substrate. The device lases under pulsed, 77K conditions at 1.54 μm with threshold current density of 1 kA/cm2 for a 100 μm × 1mm s... 详细信息

ISBN: (纸本)1424415918

关键词： Silicon

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Work in progress - Instructor credibility: An analysis of engineering students’ reflective writing for evidence of attitude shifts

Work in progress - Instructor credibility: An analysis of en...

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Frontiers in Education (FIE) Conference

作者： Linda L. Lindsley Veronica A. Burrows Science and Engineering if Materials Program Arizona State University Tempe USA Center for Research on Education in Science Mathematics Engineering and Technology and Department of Chemical Engineering Arizona State University Tempe USA

It is a common, puzzling, and often disheartening experience for teachers at all levels to realize that they may have little credibility in the eyes of their students, especially regarding the applicability of the lessons taught in the classroom to 'real world' situations. This paper analyzes the results of using a reflective writing/research paper in a freshman engineering design course to assist students in making real world connections to classroom topics. In addition to writing a standard research paper on topics related to engineering design, students were required to write a personal reflection on the assignment before and after its completion. Comparisons of these pre-assignment and post-assignment reflections show a substantial shift in the students' attitudes toward the credibility of their instructor and the choice of curriculum and topics for the course. The results also show that students spent time in metacognitive reflection on their own beliefs about the applicability of course work to the world of the working engineer. While not every student experienced these attitude shifts, review of these papers did show a substantial enough positive shift occurred through this writing process to promote further research in this area.

关键词： Writing Design engineering Reflection Process design engineering students Eyes Chemical engineering Electric breakdown Books Problem-solving

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Work in Progress - Changes in Secondary School Teachers' Attitudes Following a Course in engineering Design

Work in Progress - Changes in Secondary School Teachers' Att...

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37th Annual Frontiers in Education Conference (FIE 2007), vol.4

This paper discusses the changes in attitudes about engineering before and after an introductory course in engineering design offered to in-service secondary math and science teachers. The course is part of a series of courses offered through the NSF-sponsored MSP (Math and science Partnership): Project Pathways designed to help integrate mathematic and science and can be taken as partial fulfillment of a Master's degree in science/Math Education. An attitude survey based on the well-documented PFEAS (Pittsburgh Freshmen engineering Attitude Survey) was administered to the teachers taking the course. The survey was given at the beginning and end of the Fall 2006 semester. The greatest difference in the teachers' attitudes was in the area of engineering being perceived as an exact science. On a 5-point Likert scale, the teachers' mean responses to the group of questions regarding engineering being perceived as an exact science had a statistically significant mean difference of -.68, p<.01. The teachers showed significant differences on three other scales as well (engineering compatibility, confidence in basic engineering knowledge and skills, and overall computer skills). Additional open-ended questions showed a gain in the teachers' general knowledge about engineering as a profession and their ability to recognize students in their courses that might be successful as engineering students following their graduation from high school.

关键词： Attitudes engineering design K-12 education Teachers

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Comment on “Raman spectroscopy study of NaxCoO2 and superconducting NaxCoO2∙yH2O”

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Physical Review B 2007年第10期75卷 106501-106501页

作者： P. Lemmens P. Scheib Y. Krockenberger L. Alff F. C. Chou C. T. Lin H.-U. Habermeier B. Keimer Institute for Physics of Condensed Matter TU Braunschweig D-38106 Braunschweig Germany Max-Planck-Institute for Solid State Research Heisenbergstrasse 1 70569 Stuttgart Germany Institute of Materials Science TU Darmstadt Petersenstrasse 23 D-64287 Darmstadt Germany Center for Materials Science and Engineering MIT Cambridge Massachusetts 02139 USA

The effect of surface degradation of the thermolectric cobaltite on Raman spectra is discussed and compared to experimental results from Co3O4 single crystals. We conclude that on NaCl-flux grown NaxCoO2 crystals a surface layer of Co3O4 easily forms that leads to the observation of an intense phonon around 700cm−1 [Y. G. Shi et al., Phys. Rev. B 70, 052502 (2004)]. The Raman spectra on freshly cleaved crystals from optical floating zone ovens do not show such effects and have a high-frequency phonon cutoff at approximately 600cm−1 [P. Lemmens et al., Phys. Rev. Lett. 96, 167204 (2006)]. We discuss the relation of structural dimensionality, electronic correlations, and the high-frequency phonon cutoff of the thermolectric cobaltite.

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Magnetization oscillation in a nanomagnet driven by a self-controlled spin-polarized current: Nonlinear stability analysis

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Physical Review B 2007年第5期76卷 054414-054414页

作者： Xiao Chen Zhizhuai Zhu Yun Jing Shuai Dong Jun-Ming Liu Laboratory of Solid State Microstructures Nanjing University Nanjing 210093 China Department of Electronic Science and Engineering Nanjing University Nanjing 210093 China International Center for Materials Physics Chinese Academy of Sciences Shenyang 110015 China

The magnetization dynamics of a nanomagnet is investigated by performing macromagnetic simulation and nonlinear stability analysis on the spin precession trajectory. We propose a scheme in which a self-controlled spin-polarized current plus a magnetic field is employed to excite the self-oscillation of the magnetization through spin precession. It is revealed that the negative feedback mechanism of the spin torque is responsible for the self-oscillation excitation. The periodic solutions and the limit cycle stability for two specific configurations in terms of the directions of the spin-polarized current and magnetic field are analyzed, implying that the self-oscillation of magnetization essentially depends on the demagnetization field.

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Liquid Injection Atomic Layer Deposition of Pb(Zr,Ti)O3 Thin Films on Three Dimensional Structures

Liquid Injection Atomic Layer Deposition of Pb(Zr,Ti)O3 Thin...

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IEEE International Symposium on Applications of Ferroelectrics (ISAF)

作者： Takayuki Watanabe Susanne Hoffmann-Eifert Rainer Waser Cheol Seong Hwang Institute of Solid State Research and CNI Center for Nanoelectronic Systems and Information Technology Julich Germany Department of Materials Science and Engineering and Inter-university Semiconductor Research Center Seoul National University Seoul South Korea

A liquid injection atomic layer deposition (ALD) process has been developed for conformal deposition of lead zirconate titanate thin films on three dimensional structured silicon substrates. Future applications of these structures address the field of nonvolatile ferroelectric memory devices. PZT films were prepared by mixing the binary ALD processes of PbO x , TiO x , and ZrO x . It was found that the type of precursors as well as the stacking sequence of the binary oxide layers is crucial for the control of film stoichiometry and for a saturation of the film growth behaviour characteristic for ALD processes. Using an optimized ALD process the molar ratios of Pb/(Ti+Zr) as well as Zr/(Ti+Zr) in the films show a saturation behaviour against an increasing precursor injection volume. Pb(Zr x Ti 1-x )O 3 films deposited on 3D structured silicon exhibited a uniform film thickness and a homogeneous cation composition over the complex structure.

关键词： Atomic layer deposition Lead Silicon Semiconductor films Titanium compounds Semiconductor thin films Sputtering Substrates Nonvolatile memory Ferroelectric materials

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1.54 μm Monolithically Integrated GaSb Quantum Well Laser Diode on Silicon Operating at 77K

1.54 μm Monolithically Integrated GaSb Quantum Well Laser D...

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International Nano-Optoelectronics Workshop (i-NOW)

作者： D.L. Huffaker G. Balakrishnan A. Jallipalli M.N. Kutty J. Tatebayashi S.H. Huang L.R. Dawson Z. Mi P. Bhattacharya Center for High Technology Materials University of New Mexico Albuquerque NM USA Solid-State Electronics Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

We present a GaSb quantum well laser diode grown monolithically on a Si(100)-5° substrate. The device lases under pulsed, 77 K conditions at 1.54 μm with threshold current density of 1 kA/cm 2 for a 100 μm tim... 详细信息

关键词： Diode lasers Silicon Substrates Quantum dot lasers Optical materials Semiconductor diodes materials science and technology Threshold current III-V semiconductor materials Lattices

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