Workshop Agenda
Workshop Agenda
08.30 Hansel Center for Research on Adaptive Nanostructures and Nanodevices. Trinity College, Dublin
Eddy currents and measurements in pulsed magnetic fields
Performing experiments in pulsed magnetic fields, eddy currents are the effect that you love to ignore whenever you don't attach wires to your reasonably well conducting sample. However, even optical investigations in pulsed field, especially the single turn coil, have been shown do be considerably affected by them. I am going to present a very basic theory for their quantification and show how to estimate their effects such as voltages, heating and internally applied pressure and thus understand experimental curves or even correct them into more reasonable ones. Moreover, I am going to show how lessons learned from the single turn coil enable us to develop measurement techniques based on eddy currents effects such as quantitative resonant circuits experiments simultaneously determining susceptibility and conductivity contactlessly.
09.05 Chuck Mielke NHMFL –PFF Los Alamos National laboratory
Extreme Perturbations: Beyond 100 T
Magnetic field generation in excess of 100 tesla currently requires a system that is in part destructive to the magnet itself.
At the NHMFL-PFF a system which employs the Single Turn technique is now mature and routinely delivering a research magnetic field of 170 tesla with successful tests to 240 tesla. Measurement techniques in this hostile environment with dB/dt rates in excess of 100 million tesla/second are extreme challenges in themselves. Optical techniques have produced some of the best achievable signal:noise and will be highlighted as applied to condensed matter systems. A significant effort towards realization of a resistivity technique in which inductive coupling to the metallic sample will be discussed along with preliminary results.
09.40 Oliver Portugal Laboratoire National des Champs Magnétiques Intenses CNRS, Toulouse, FRANCE
The Toulouse pulsed magnet facility - recent developments and future plans
The main part of this talk will be dedicated to a general overview over the experimental possibilities of the Toulouse pulsed magnet facility (generators, magnets, cryogenic equipment and experimental techniques) as well as selected scientific results. I will then discuss some of the ongoing technical developments and projects, in particular the construction of a 6 MJ mobile capacitor bank and the development of new experimental techniques to be used in connection with highly transient (< 10 us) Megagauss fields (> 100 T). The talk will also include a brief explanation of the current organization and future plans of the EuroMagNET consortium which comprises the four major high-field facilities in Europe.
--10.15 coffee break--
10.30 Doug Tasker High Explosives Applications and Special Projects. Los Alamos National Laboratory
Isentropic compression studies using the NHMFL Single Turn
Magnetic isentropic compression experiments (ICE) provide the most accurate shock free compression data for materials at megabar pressures. Recent ICE experiments performed on the Sandia Z-machine and at the Los Alamos High Explosive Pulsed Power facility are providing our nation with data on material properties in extreme dynamic high pressure environments. The NHMFL can offer a less complex ICE experiment at modest pressures (up to 1 Mbar) with a high sample throughput and relatively low cost. We will discuss the physics of the NHMFL-ICE experiments and present data from the first proof-of-principle experiments.
11.05 Madalina Furis University of Vermont Burlington, VT
Challenges of Optical Spectroscopy in High Magnetic Fields
High magnetic fields play a crucial role in the investigation of spin-dependent phenomena in a large variety of materials ranging from semiconductors, ferroic materials, and superconductors to biomolecules and living tissues. Many of these phenomena leave their signature on the optical properties of these materials. Examples include the magnetization-induced circular birefringence (Faraday and Kerr effects) observed in ferromagnetic or paramagnetic systems, magnetic circular dichroism (MCD) of semiconductors or organic molecules, circularly-polarized radiative recombination of spin-polarized electrons in semiconductor nanostructures, luminescence from optically-forbidden states in carbon nanotubes and semiconductors nanocrystals, spin-flip Raman transitions. In this talk I will review the principles and challenges of high magnetic field optical spectroscopy experiments that investigate these phenomena, focusing on the successes as well as limitations of fiber-coupled optical techniques in pulsed magnetic fields. Examples of unique observations enabled by non-destructive pulsed B fields larger than 60T include a dark exciton ground state and an Aharonov –Bohm phase in carbon nanotubes, or exciton g-factors in semiconductor nanocrystals. At the same time, the short duration of pulses (< 2 sec) and, in some cases, the lack of polarization control, limits severely limits studies of magnetic circular dichroism in thin films or ultrafast spin dynamics.
11.40 Philip Moll Laboratory for Solid State Physics, ETH Zurich, Switzerland
Ion Beam Sample Preparation for Pulsed Magnetic Fields: Application to Pnictides
The Focused Ion Beam (FIB) is a versatile high precision tool for material manipulation on the micro- and nanoscale. We present recently developed FIB based techniques giving precise control over the sample geometry and electrical behavior. This technique has in the past proven to be an ideal method to prepare sophisticated electronic transport samples out of microscopic crystals. These samples feature controllable absolute resistance, very low contact resistances, multiple measurements on one crystal, selection of crystal axes and extremely large Signal-to-Noise ratios, even in pulsed magnetic fields. We have very successfully applied this technique to study the anisotropy of the superconducting properties and critical currents in the pnictide superconductor SmFeAs(O,F) (Tc~55K) to assess the materials potential for application. The intragrain low temperature properties are promising: We found a combination of high (> 106 A/cm2) and almost isotropic critical currents and only little influence of the current orientation in the crystal.
--12.15 Lunch and badging--
13.45 Zahirul Islam Advanced Photon Source, Argonne National Laboratory
Tools and techniques for precision x-ray studies of materials in pulsed magnetic fields
Pulsed magnets have emerged as a viable tool for studying materials using high-resolution structural probes at modern synchrotron facilities. A diversity of condensed-matter systems are being studied to determine field-induced structural and magnetic effects such as magneto-striction, Jahn-Teller distortions, and phase transitions using a number of x-ray diffraction and spectroscopic techniques. An overview of some representative x-ray studies is presented in this talk. At the APS efforts have been underway for advancing the use of three complementary 30 Tesla pulsed magnet systems. Two unique instruments have already been developed, which are compact, portable, and do not require special infrastructure. The first magnet is a split pair of mini-coils (pulse duration ~1ms) with applied field normal to the scattering plane [1], which has recently been used in the study of magneto-elastics of a spin-liquid system [2]. The second is a large-bore solenoid (pulse duration ~4ms) that allows fields to be in the scattering plane. The coils have been designed and built at Tohoku University. Finally, a conceptual design for a novel asymmetric “hour-glass” magnet has been developed in collaboration with NHMFL-PFF. This set of three pulsed-magnet instruments would allow a wide range of problems to be studied using various x-ray scattering and spectroscopic techniques.
[1] Zahirul Islam, Jacob P. C. Ruff, Hiroyuki Nojiri, Yasuhiro H. Matsuda, Kathryn A. Ross, Bruce D. Gaulin, Zhe Qu, Jonathan C. Lang, Rev. Sci. Instrum. 80, 113902 (2009).
[2] J. P. C. Ruff, Z. Islam, J. P. Clancy, K. A. Ross, H. Nojiri, Y. H. Matsuda, K. A. Ross, H. A. Dabkowska, and B. D. Gaulin, Phys. Rev. Lett. 105, 077203 (2010).
Use of the APS is supported by the U. S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
14.20 David Morris Director, Center for Integrated Nanotechnologies (CINT) Los Alamos
Research Opportunities at CINT: A DOE / BES Nanoscale Science Research Center
CINT, the Center for Integrated Nanotechnologies, is one of five Nanoscale Science Research Centers operated by the US Department of Energy Office of Science as a national user facility resource to promote and enable research in all aspects of nanoscience. CINT is differentiated from the other DOE NSRCs by its focus on nanoscience integration and by the fact that it is a joint venture of two DOE national laboratories; Los Alamos and Sandia National Laboratories. CINT also benefits from its colocation and historic strong collaborative interactions at Los Alamos with the National High Magnetic Field Lab and the Lujan Neutron Scattering Center. Together, these three national user facilities with operations at LANL comprise an enormous opportunity for discovery science that spans biology, chemistry, materials science, and physics. The focus of this talk will be on the structure of CINT and the extant capabilities for nanomaterials science research at both LANL Gateway and Sandia Core facilities, and details of our user facility operations including our user proposal process.
14.55 Alan Hurd Los Alamos Neutron Science Center (LANSCE)
Research opportunities and neutron scattering for complex materials
Human ingenuity continues to produce new materials that require a fresh look at how we solve materials physics problems with neutrons, which have a particular advantage in magnetically active materials. The trend in synthesis is toward ever finer inhomogeneity of ever greater differences, which has been fruitful for pursuing ever higher performance density. Practitioners of neutron diffraction, inelastic scattering, and large-scale scattering techniques have sharpened their pencils significantly in the last decade, with higher flux sources and better detectors, to study exotic materials such as MAX phases, Laves phases, metal-oxide frameworks, archaeological speciments, and nanostructured materials to name just a few. Many new techniques have been developed, notably “total scattering” to obtain pair distribution functions (pdf) and dynamic pdfs. Perhaps the greatest progress has been in sample environments and auxiliary equipment: For example, it is now possible to apply over 200 kN to a sample in a neutron beam at temperatures from liquid nitrogen to 2200C. A dilution refrigerator is under commissioning as well. Through a call for Letters of Intent, users have grouped around fresh new instrumentation ideas as part of the Enhanced Lujan Program. Recent results taken mostly from LANSCE will be reviewed, highlighting cases where new techniques have encouraged the unearthing of complexity in behaviour.
15.30 Marcelo Jaime NHMFL –PFF Los Alamos National Laboratory
Modulation calorimetry in Pulsed magnetic fields
A new calorimeter for measurements of the heat capacity and magnetocaloric effect of small samples in pulsed magnetic fields is discussed for the exploration of thermal properties at temperatures down to 1 K. We tested the method in both DC and pulsed magnetic fields up to m0H = 55 Tesla, but it could be extended to higher fields. Heat capacity and magnetocaloric effect for the spin-dimer compound Sr3Cr2O8, the triangular lattice antiferromagnet RbFe(MoO4)2, the quantum magnet Pb2V3O9 and the heavy fermion CeIrIn5 will be discussed as illustration of the capability.