Open Access. Powered by Scholars. Published by Universities.®

Physics Commons

Open Access. Powered by Scholars. Published by Universities.®

Series

Magnetic fields

Discipline
Institution
Publication Year
Publication

Articles 1 - 30 of 60

Full-Text Articles in Physics

All-Optical Atom Trap As A Target For Motrims-Like Collision Experiments, S. Sharma, B. P. Acharya, Daniel Fischer, For Full List Of Authors, See Publisher's Website. Apr 2018

All-Optical Atom Trap As A Target For Motrims-Like Collision Experiments, S. Sharma, B. P. Acharya, Daniel Fischer, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

Momentum-resolved scattering experiments with laser-cooled atomic targets have been performed since almost two decades with magneto-optical trap recoil ion momentum spectroscopy (MOTRIMS) setups. Compared to experiments with gas-jet targets, MOTRIMS features significantly lower target temperatures allowing for an excellent recoil ion momentum resolution. However, the coincident and momentum-resolved detection of electrons was long rendered impossible due to incompatible magnetic field requirements. Here we report on an experimental approach which is based on an all-optical 6Liatom trap that--in contrast to magneto-optical traps--does not require magnetic field gradients in the trapping region. Atom temperatures of about 2 mK and number densities ...


Ion Parallel Closures, Jeong-Young Ji, Hankyu Q. Lee, Eric D. Held Dec 2017

Ion Parallel Closures, Jeong-Young Ji, Hankyu Q. Lee, Eric D. Held

All Physics Faculty Publications

Ion parallel closures are obtained for arbitrary atomic weights and charge numbers. For arbitrary collisionality, the heat flow and viscosity are expressed as kernel-weighted integrals of the temperature and flow-velocity gradients. Simple, fitted kernel functions are obtained from the 1600 parallel moment solution and the asymptotic behavior in the collisionless limit. The fitted kernel parameters are tabulated for various temperature ratios of ions to electrons. The closures can be used conveniently without solving the kinetic equation or higher order moment equations in closing ion fluid equations.


Engineering Electron Superpositions Using A Magnetic Field, Zoe A. Rowley, Bianca R. Gualtieri Jul 2017

Engineering Electron Superpositions Using A Magnetic Field, Zoe A. Rowley, Bianca R. Gualtieri

Physics and Astronomy Summer Fellows

A Rydberg atom has a highly excited valence electron which is weakly bound and far from the nucleus. These atoms have exaggerated properties that make them attractive candidates for quantum computation and studies of fundamental quantum mechanics. The discrete energy levels of Rydberg atoms are shifted in the presence of an electric field by the Stark effect and are similarly shifted due to a magnetic field by the Zeeman effect. These effects couple the energy levels together, creating avoiding crossings. At these avoided crossings, an electron in one energy level can jump to the other.

Our goal is to be ...


Interactions Between Uniformly Magnetized Spheres, Boyd F. Edwards, D. Mark Riffe, Jeong-Young Ji, William A. Booth Feb 2017

Interactions Between Uniformly Magnetized Spheres, Boyd F. Edwards, D. Mark Riffe, Jeong-Young Ji, William A. Booth

All Physics Faculty Publications

We use simple symmetry arguments suitable for undergraduate students to demonstrate that the magnetic energy, forces, and torques between two uniformly magnetized spheres are identical to those between two point magnetic dipoles. These arguments exploit the equivalence of the field outside of a uniformly magnetized sphere with that of a point magnetic dipole, and pertain to spheres of arbitrary sizes, positions, and magnetizations. The point dipole/sphere equivalence for magnetic interactions may be useful in teaching and research, where dipolar approximations for uniformly magnetized spheres can now be considered to be exact. The work was originally motivated by interest in ...


Magnetization Reversal In Ferromagnetic Spirals Via Domain Wall Motion, Ryan D. Schumm, Andrew Kunz Nov 2016

Magnetization Reversal In Ferromagnetic Spirals Via Domain Wall Motion, Ryan D. Schumm, Andrew Kunz

Physics Faculty Research and Publications

Domain wall dynamics have been investigated in a variety of ferromagnetic nanostructures for potential applications in logic, sensing, and recording. We present a combination of analytic and simulated results describing the reliable field driven motion of a domain wall through the arms of a ferromagnetic spiral nanowire. The spiral geometry is capable of taking advantage of the benefits of both straight and circular wires. Measurements of the in-plane components of the spirals' magnetization can be used to determine the angular location of the domain wall, impacting the magnetoresistive applications dependent on the domain wall location. The spirals' magnetization components are ...


Orion's Veil: Magnetic Field Strengths And Other Properties Of A Pdr In Front Of The Trapezium Cluster, Thomas H. Troland, W. M. Goss, C. L. Brogan, R. M. Crutcher, D. A. Roberts Jun 2016

Orion's Veil: Magnetic Field Strengths And Other Properties Of A Pdr In Front Of The Trapezium Cluster, Thomas H. Troland, W. M. Goss, C. L. Brogan, R. M. Crutcher, D. A. Roberts

Physics and Astronomy Faculty Publications

We present an analysis of physical conditions in the Orion Veil, an atomic photon-dominated region (PDR) that lies just in front (≈2 pc) of the Trapezium stars of Orion. This region offers an unusual opportunity to study the properties of PDRs, including the magnetic field. We have obtained 21 cm H i and 18 cm (1665 and 1667 MHz) OH Zeeman effect data that yield images of the line-of-sight magnetic field strength B los in atomic and molecular regions of the Veil. We find B los ≈ −50 to −75 μG in the atomic gas across much of the Veil ...


Orion's Veil. Iv. H2 Excitation And Geometry, N. P. Abel, Gary J. Ferland, C. R. O'Dell, Thomas H. Troland Mar 2016

Orion's Veil. Iv. H2 Excitation And Geometry, N. P. Abel, Gary J. Ferland, C. R. O'Dell, Thomas H. Troland

Physics and Astronomy Faculty Publications

The foreground Veil of material that lies in front of the Orion Nebula is the best studied sample of the interstellar medium because we know where it is located, how it is illuminated, and the balance of thermal and magnetic energy. In this work, we present high-resolution STIS observations toward the Trapezium, with the goal of better understanding the chemistry and geometry of the two primary Veil layers, along with ionized gas along the line of sight. The most complete characterization of the rotational/vibrational column densities of H2 in the almost purely atomic components of the Veil are ...


Selection And Control Of Individual Domain Walls In Nanowire Arrays Via Asymmetric Depinning Fields, Andrew Kunz, H. Henry Le, Demetrious Kutzke, Jesse Vogeler-Wunsch Feb 2016

Selection And Control Of Individual Domain Walls In Nanowire Arrays Via Asymmetric Depinning Fields, Andrew Kunz, H. Henry Le, Demetrious Kutzke, Jesse Vogeler-Wunsch

Physics Faculty Research and Publications

Artificially inscribed notches are often used to pin domain walls (DWs) in ferromagnetic nanowires. The process of selecting and moving the trapped DW in nanowire arrays is an important step for potential applications. The chirality of a DW leads to a pair of pinning positions at the inscribed notches, which can be modeled by a symmetric double well. The depinning field depends on the side of the well, the DW is trapped with respect to the applied field direction, and the DWs can also be transitioned between the two wells without depinning. We demonstrate how manipulating the double well improves ...


Electron Heat Flow Due To Magnetic Field Fluctuations, Jeong-Young Ji, Gunyoung Park, Sung Sik Kim, Eric D. Held Jan 2016

Electron Heat Flow Due To Magnetic Field Fluctuations, Jeong-Young Ji, Gunyoung Park, Sung Sik Kim, Eric D. Held

All Physics Faculty Publications

Radial heat transport induced by magnetic field line fluctuations is obtained from the integral parallel heat flow closure for arbitrary collisionality. The parallel heat flow and its radial component are computed for a single harmonic sinusoidal field line perturbation. In the collisional and collisionless limits, averaging the heat flow over an unperturbed surface yields Rechester-Rosenbluth like formulae with quantitative factors. The single harmonic result is generalized to multiple harmonics given a spectrum of small magnetic perturbations. In the collisionless limit, the heat and particle transport relations are also derived. © 2016 IOP Publishing Ltd.


Multi-Frequency Ferromagnetic Resonance Investigation Of Nickel Nanocubes Encapsulated In Diamagnetic Magnesium Oxide Matrix, Saritha Nellutla, Sudhakar Nori, Srinivasa R. Singamaneni, John T. Prater, Jagdish Narayan, Alix I. Smirnov Jan 2016

Multi-Frequency Ferromagnetic Resonance Investigation Of Nickel Nanocubes Encapsulated In Diamagnetic Magnesium Oxide Matrix, Saritha Nellutla, Sudhakar Nori, Srinivasa R. Singamaneni, John T. Prater, Jagdish Narayan, Alix I. Smirnov

Chemical Sciences Faculty Publications

Partially aligned nickel nanocubes were grown epitaxially in a diamagnetic magnesium oxide (MgO:Ni) host and studied by a continuous wave ferromagnetic resonance (FMR) spectroscopy at the X-band (9.5 GHz) from ca. 117 to 458 K and then at room temperature for multiple external magnetic fields/resonant frequencies from 9.5 to 330 GHz. In contrast to conventional magnetic susceptibility studies that provided data on the bulk magnetization, the FMR spectra revealed the presence of three different types of magnetic Ni nanocubes in the sample. Specifically, three different ferromagnetic resonances were observed in the X-band spectra: a line 1 ...


A Method For Measuring The Néel Relaxation Time In A Frozen Ferrofluid, Ronald J. Tackett, Jagdish Thakur, Nathaniel Mosher, Emily Perkins-Harbin, Ronald E. Kumon, Lihua Wang, Corneliu Rablau, Prem P. Vaishnava Aug 2015

A Method For Measuring The Néel Relaxation Time In A Frozen Ferrofluid, Ronald J. Tackett, Jagdish Thakur, Nathaniel Mosher, Emily Perkins-Harbin, Ronald E. Kumon, Lihua Wang, Corneliu Rablau, Prem P. Vaishnava

Physics Publications

We report a novel method of determining the average Néel relaxation time and its temperature dependence by calculating derivatives of the measured time dependence of temperature for a frozen ferrofluid exposed to an alternating magnetic field. The ferrofluid, composed of dextran-coated Fe3O4 nanoparticles (diameter 13.7 nm ± 4.7 nm), was synthesized via wet chemical precipitation and characterized by x-ray diffraction and transmission electron microscopy. An alternating magnetic field of constant amplitude (H0=20H0=20 kA/m) driven at frequencies of 171 kHz, 232 kHz, and 343 kHz was used to determine the temperature dependent magnetic energy absorption rate in ...


A Sensitive Faraday Rotation Setup Using Triple Modulation, G. Phelps, Josh Abney, Mark Broering, Wolfgang Korsch Jul 2015

A Sensitive Faraday Rotation Setup Using Triple Modulation, G. Phelps, Josh Abney, Mark Broering, Wolfgang Korsch

Physics and Astronomy Faculty Publications

The utilization of polarized targets in scattering experiments has become a common practice in many major accelerator laboratories. Noble gases are especially suitable for such applications, since they can be easily hyper-polarized using spin exchange or metastable pumping techniques. Polarized helium-3 is a very popular target because it often serves as an effective polarized neutron due to its simple nuclear structure. A favorite cell material to generate and store polarized helium-3 is GE-180, a relatively dense aluminosilicate glass. In this paper, we present a Faraday rotation method, using a new triple modulation technique, where the measurement of the Verdet constants ...


Phenomenology Of N- Oscillations Revisited, Susan Gardner, Ehsan Jafari May 2015

Phenomenology Of N-N̄ Oscillations Revisited, Susan Gardner, Ehsan Jafari

Physics and Astronomy Faculty Publications

We revisit the phenomenology of n−n̄ oscillations in the presence of external magnetic fields, highlighting the role of spin. We show, contrary to long-held belief, that the n−n̄ transition rate need not be suppressed, opening new opportunities for its empirical study.


A Slow Neutron Polarimeter For The Measurement Of Parity-Odd Neutron Rotary Power, W. M. Snow, E. Anderson, L. Barrón-Palos, C. D. Bass, T. D. Bass, B. E. Crawford, Christopher Crawford, J. M. Dawkins, D. Esposito, J. Fry, H. Gardiner, K. Gan, C. Haddock, B. R. Heckel, A. T. Holley, J. C. Horton, C. Huffer, J. Lieffers, D. Luo, M. Maldonado-Velázquez, D. M. Markoff, A. M. Micherdzinska, H. P. Mumm, J. S. Nico, M. Sarsour, S. Santra, E. I. Sharapov, H. E. Swanson, S. B. Walbridge, V. Zhumabekova May 2015

A Slow Neutron Polarimeter For The Measurement Of Parity-Odd Neutron Rotary Power, W. M. Snow, E. Anderson, L. Barrón-Palos, C. D. Bass, T. D. Bass, B. E. Crawford, Christopher Crawford, J. M. Dawkins, D. Esposito, J. Fry, H. Gardiner, K. Gan, C. Haddock, B. R. Heckel, A. T. Holley, J. C. Horton, C. Huffer, J. Lieffers, D. Luo, M. Maldonado-Velázquez, D. M. Markoff, A. M. Micherdzinska, H. P. Mumm, J. S. Nico, M. Sarsour, S. Santra, E. I. Sharapov, H. E. Swanson, S. B. Walbridge, V. Zhumabekova

Physics and Astronomy Faculty Publications

We present the design, description, calibration procedure, and an analysis of systematic effects for an apparatus designed to measure the rotation of the plane of polarization of a transversely polarized slow neutron beam as it passes through unpolarized matter. This device is the neutron optical equivalent of a crossed polarizer/analyzer pair familiar from light optics. This apparatus has been used to search for parity violation in the interaction of polarized slow neutrons in matter. Given the brightness of existing slow neutron sources, this apparatus is capable of measuring a neutron rotary power of dϕ/dz = 1 × 10−7 rad ...


Magnetic Fields, Voltage, And Currents Problems (Practice Questions), Arun Saha Apr 2015

Magnetic Fields, Voltage, And Currents Problems (Practice Questions), Arun Saha

Physics and Astronomy Ancillary Materials

This set of lecture-oriented practice questions was developed under a Round One ALG Textbook Transformation Grant.


Magnetic Response Of Aperiodic Wire Networks Based On Fibonacci Distortions Of Square Antidot Lattices, Barry Farmer, Vinayak Bhat, J. Sklenar, Eric Teipel, Justin Woods, J. B. Ketterson, J. Todd Hastings, Lance Delong Mar 2015

Magnetic Response Of Aperiodic Wire Networks Based On Fibonacci Distortions Of Square Antidot Lattices, Barry Farmer, Vinayak Bhat, J. Sklenar, Eric Teipel, Justin Woods, J. B. Ketterson, J. Todd Hastings, Lance Delong

Physics and Astronomy Faculty Publications

The static and dynamic magnetic responses of patterned ferromagnetic thin films are uniquely altered in the case of aperiodic patterns that retain long-range order (e.g., quasicrystals). We have fabricated permalloy wire networks based on periodic square antidot lattices (ADLs) distorted according to an aperiodic Fibonacci sequence applied to two lattice translations, d1  = 1618 nm and d2  = 1000 nm. The wire segment thickness is fixed at t = 25 nm, and the width W varies from 80 to 510 nm. We measured the DC magnetization between room temperature and 5 K. Room-temperature, narrow-band (9.7 GHz) ferromagnetic resonance (FMR ...


Temperature Dependence Of Anisotropic Magnetoresistance In Antiferromagnetic Sr2Iro4, C. Wang, H. Seinige, Gang Cao, J.-S. Zhou, J. B. Goodenough, M. Tsoi Feb 2015

Temperature Dependence Of Anisotropic Magnetoresistance In Antiferromagnetic Sr2Iro4, C. Wang, H. Seinige, Gang Cao, J.-S. Zhou, J. B. Goodenough, M. Tsoi

Center for Advanced Materials Faculty Publications

Temperature-dependent magnetotransport properties of the antiferromagnetic semiconductor Sr2IrO4 are investigated with point-contact devices. The point-contact technique allows to probe very small volumes and, therefore, to look for electronic transport on a microscopic scale. Point-contact measurements with single crystals of Sr2IrO4 were intended to see whether the additional local resistance associated with a small contact area between a sharpened Cu tip and the antiferromagnet shows magnetoresistance (MR) such as that seen in bulk crystals. Point-contact measurements at liquid nitrogen temperature revealed large MRs (up to 28%) for modest magnetic fields (250 mT) applied within an ...


Electromechanical Magnetization Switching, Eugene M. Chudnovsky, Reem Jaafar Feb 2015

Electromechanical Magnetization Switching, Eugene M. Chudnovsky, Reem Jaafar

Publications and Research

We show that the magnetization of a torsional oscillator that, in addition to the magnetic moment also possesses an electrical polarization, can be switched by the electric field that ignites mechanical oscillations at the frequency comparable to the frequency of the ferromagnetic resonance. The 180° switching arises from the spin-rotation coupling and is not prohibited by the different symmetry of the magnetic moment and the electric field as in the case of a stationary magnet. Analytical equations describing the system have been derived and investigated numerically. Phase diagrams showing the range of parameters required for the switching have been obtained.


Second Order Phase Transition Temperature Of Single Crystals Of Gd5si1.3ge2.7 And Gd5si1.4ge2.6, Ravi L. Hadimani, Yevgen Melikhov, Deborah L. Schlagel, Thomas A. Lograsso, Kevin W. Dennis, R. William Mccallum, David C. Jiles Jan 2015

Second Order Phase Transition Temperature Of Single Crystals Of Gd5si1.3ge2.7 And Gd5si1.4ge2.6, Ravi L. Hadimani, Yevgen Melikhov, Deborah L. Schlagel, Thomas A. Lograsso, Kevin W. Dennis, R. William Mccallum, David C. Jiles

Electrical and Computer Engineering Publications

Gd5(Six Ge 1−x)4 has mixed phases in the composition range 0.32 < x < 0.41, which have not been widely studied. In this paper, we have synthesized and indexed single crystal samples of Gd5Si1.3 Ge 2.7 and Gd5Si1.4 Ge 2.6. We have investigated the first order and second orderphase transition temperatures of these samples using magnetic moment vs. temperature andmagnetic moment vs. magnetic field at different temperatures. We have used a modified Arrott plot technique that was developed and reported by us previously to determine the “hidden” second order phase transition temperature of the orthorhombic II phase.


Deep Brain Transcranial Magnetic Stimulation Using Variable “Halo Coil” System, Y. Meng, Ravi L. Hadimani, Lawrence J. Crowther, Z. Xu, J. Qu Jan 2015

Deep Brain Transcranial Magnetic Stimulation Using Variable “Halo Coil” System, Y. Meng, Ravi L. Hadimani, Lawrence J. Crowther, Z. Xu, J. Qu

Electrical and Computer Engineering Publications

Transcranial Magnetic Stimulation has the potential to treat various neurological disorders non-invasively and safely. The “Halo coil” configuration can stimulate deeper regions of the brainwith lower surface to deep-brain field ratio compared to other coil configurations. The existing “Halo coil” configuration is fixed and is limited in varying the site of stimulation in the brain. We have developed a new system based on the current “Halo coil” design along with a graphicaluser interface system that enables the larger coil to rotate along the transverse plane. The new system can also enable vertical movement of larger coil. Thus, this adjustable “Halo ...


A Facility For Magnetic Field Penetration Measurements On Multilayer S-I-S Structures, Oleg B. Malyshev, Lewis Gurran, Shrikant Pattalwar, Ninad Pattalwar, Keith D. Dumbell, Reza Valizadeh, Alex Gurevich Jan 2015

A Facility For Magnetic Field Penetration Measurements On Multilayer S-I-S Structures, Oleg B. Malyshev, Lewis Gurran, Shrikant Pattalwar, Ninad Pattalwar, Keith D. Dumbell, Reza Valizadeh, Alex Gurevich

Physics Faculty Publications

Superconducting RF cavities made of bulk Nb has reached a breakdown field of about 200 mT which is close to the superheating field for Nb. As it was theoretically shown a multilayer coating can be used to enhance the breakdown field of SRF cavities. The simple example is a superconductor-insulator-superconductor (S-I-S), for example bulk niobium (S) coated with a thin film of insulator (I) followed by a thin layer of a superconductor (S) which could be a dirty niobium. To verify such an enhancement in a presence of a DC magnetic field at 4.2 K a simple experimental facility ...


Magnet Traveling Through A Conducting Pipe: A Variation On The Analytical Approach, Benjamin Irvine, Matthew Kemnetz, Asim Gangopadhyaya, Thomas Ruubel Apr 2014

Magnet Traveling Through A Conducting Pipe: A Variation On The Analytical Approach, Benjamin Irvine, Matthew Kemnetz, Asim Gangopadhyaya, Thomas Ruubel

Physics: Faculty Publications and Other Works

We present an analytical study of magnetic damping. In particular, we investigate the dynamics of a cylindrical neodymium magnet as it moves through a conducting tube. Owing to the very high degree of uniformity of the magnetization for neodymium magnets, we are able to provide completely analytical results for the electromotive force generated in the pipe and the consequent retarding force. Our analytical expressions are shown to have excellent agreement with experimental observations.


The Creation Of 360° Domain Walls In Ferromagnetic Nanorings By Circular Applied Magnetic Fields, Jessica E. Bickel, Spencer A. Smith, Katherine E. Aidala Feb 2014

The Creation Of 360° Domain Walls In Ferromagnetic Nanorings By Circular Applied Magnetic Fields, Jessica E. Bickel, Spencer A. Smith, Katherine E. Aidala

Physics Faculty Publications

Switching behavior in ferromagnetic nanostructures is often determined by the formation and annihilation of domain walls (DWs). In contrast to the more familiar 180° DWs found in most nanostructures, 360° DWs are the proposed transition state of nanorings. This paper examines the formation of 360° DWs created by the application of a circular magnetic field using micromagnetic simulations. 360° DWs form from pairs of canting moments that are oppositely aligned, which each grow to form rotated domains bounded by two 180° DWs and the 180° DWs combine to form 360° DWs. The resulting 360° DWs occur in pairs of opposite ...


Phenomenological Modelling Of First Order Phase Transitions In Magnetic Systems, Yevgen Melikhov, Ravi L. Hadimani, Arun Raghunathan Jan 2014

Phenomenological Modelling Of First Order Phase Transitions In Magnetic Systems, Yevgen Melikhov, Ravi L. Hadimani, Arun Raghunathan

Electrical and Computer Engineering Publications

First order phase transitions may occur in several magnetic systems, with two structural phases having different magnetic properties each and a structural transition between them. Here, a novel physics based phenomenological model of such systems is proposed, in which magnetization is represented by the volumetric amounts of ferromagnetism (described by extended Jiles-Atherton theory) and paramagnetism (described by the Curie-Weiss law) in respective phases. An identification procedure to extract material parameters from experimental data is proposed. The proposed phenomenological approach was successfully applied to magnetocaloric Gd5(Six Ge 1−x)4 system and also has the potential to describe the behavior ...


Estimations Of The Magnetic Field Strength In The Torus Of Ic 5063 Using Near-Infrared Polarimetry, E. Lopez-Rodriguez, C. Packham, S. Young, Moshe Elitzur, N. A. Levenson, R. E. Mason, C. Ramos Almeida, A. Alonso-Herrero, T. J. Jones, E. Perlman May 2013

Estimations Of The Magnetic Field Strength In The Torus Of Ic 5063 Using Near-Infrared Polarimetry, E. Lopez-Rodriguez, C. Packham, S. Young, Moshe Elitzur, N. A. Levenson, R. E. Mason, C. Ramos Almeida, A. Alonso-Herrero, T. J. Jones, E. Perlman

Physics and Astronomy Faculty Publications

An optically and geometrically thick torus obscures the central engine of active galactic nuclei (AGN) from some lines of sight. From a magnetohydrodynamical framework, the torus can be considered to be a particular region of clouds surrounding the central engine where the clouds are dusty and optically thick. In this framework, the magnetic field plays an important role in the creation, morphology and evolution of the torus. If the dust grains within the clouds are assumed to be aligned by paramagnetic alignment, then the ratio of the intrinsic polarization and visual extinction, P(per cent)/Av, is a function ...


Strongly Localized Magnetization Modes In Permalloy Antidot Lattices, J. Sklenar, V. S. Bhat, Lance E. De Long, O. Heinonen, J. B. Ketterson Apr 2013

Strongly Localized Magnetization Modes In Permalloy Antidot Lattices, J. Sklenar, V. S. Bhat, Lance E. De Long, O. Heinonen, J. B. Ketterson

Physics and Astronomy Faculty Publications

Antidot lattices (ADLs) patterned into soft magnetic thin films exhibit rich ferromagnetic resonance (FMR) spectra corresponding to many different magnetization modes. One of the predicted modes is highly localized at the edges of the antidots; this mode is difficult to detect experimentally. Here we present FMR data for a permalloy thin film patterned into a square array of square antidots. Comparison of these data with micromagnetic simulations permits identification of several edge modes. Our simulations also reveal the effect of the antidot shape on the mode dispersion.


A Novel Approach For X-Ray Scattering Experiments In Magnetic Fields Utilizing Trapped Flux In Type-Ii Superconductors, R. K. Das, Z. Islam, J. P. C. Ruff, R. P. Sawh, R. Winstein, Paul C. Canfield, J.-W. Kim, J. C. Lang Jan 2012

A Novel Approach For X-Ray Scattering Experiments In Magnetic Fields Utilizing Trapped Flux In Type-Ii Superconductors, R. K. Das, Z. Islam, J. P. C. Ruff, R. P. Sawh, R. Winstein, Paul C. Canfield, J.-W. Kim, J. C. Lang

Ames Laboratory Publications

We introduce a novel approach to x-ray scattering studies in applied magnetic fields by exploiting vortices in superconductors. This method is based on trapping magnetic flux in a small disk-shaped superconductor (known as a trapped field magnet, TFM) with a single-crystal sample mounted on or at close proximity to its surface. This opens an unrestricted optical access to the sample and allows magnetic fields to be applied precisely along the x-ray momentum transfer, facilitating polarization-sensitive experiments that have been impractical or impossible to perform to date. The TFMs used in our study remain stable and provide practically uniform magnetic fields ...


A Single-Solenoid Pulsed-Magnet System For Single-Crystal Scattering Studies, Zahirul Islam, Dana Capatina, Jacob P. C. Ruff, Ritesh K. Das, Emil Trakhtenberg, Hiroyuki Nojiri, Yasuo Narumi, Ulrich Welp, Paul C. Canfield Jan 2012

A Single-Solenoid Pulsed-Magnet System For Single-Crystal Scattering Studies, Zahirul Islam, Dana Capatina, Jacob P. C. Ruff, Ritesh K. Das, Emil Trakhtenberg, Hiroyuki Nojiri, Yasuo Narumi, Ulrich Welp, Paul C. Canfield

Ames Laboratory Publications

We present a pulsed-magnet system that enables x-raysingle-crystaldiffraction in addition to powder and spectroscopic studies with the magnetic field applied on or close to the scattering plane. The apparatus consists of a single large-bore solenoid, cooled by liquid nitrogen. A second independent closed-cycle cryostat is used for cooling samples near liquid helium temperatures. Pulsed magnetic fields close to ∼30 T with a zero-to-peak-field rise time of ∼2.9 ms are generated by discharging a 40 kJ capacitor bank into the magnet coil. The unique characteristic of this instrument is the preservation of maximum scattering angle (∼23.6°) on the entrance ...


Quantum Griffiths Phase In The Weak Itinerant Ferromagnetic Alloy Ni1-XVX, Sara Ubaid-Kassis, Thomas Vojta, Almut Schroeder Feb 2010

Quantum Griffiths Phase In The Weak Itinerant Ferromagnetic Alloy Ni1-XVX, Sara Ubaid-Kassis, Thomas Vojta, Almut Schroeder

Physics Faculty Research & Creative Works

We present magnetization (M) data of the d-metal alloy Ni1-xVx at vanadium concentrations close to xx ~ 11.4% where the onset of long-range ferromagnetic (FM) order is suppressed to zero temperature. Above xc, the temperature (T) and magnetic field (H) dependencies of the magnetization are best described by simple nonuniversal power laws. the exponents of M/H ~ T γ and M ~ Hα are related by 1-γ=α for wide temperature (10c to γ<0.1 for x=15%. This behavior is not compatible with either classical or quantum critical behavior in a clean 3D FM. Instead it closely follows the predictions for a quantum Griffiths phase associated with a quantum phase transition in a disordered metal. Deviations at the lowest temperatures hint at a freezing of large clusters and the onset of a cluster glass phase.


Total Solar Eclipse Observations Of Hot Prominence Shrouds, Shadia Rifai Habbal, Miloslav Druckmüller, Huw Morgan, I. Scholl, V. Rusin, Adrian Daw, Judd Johnson, Martina B. Arndt Jan 2010

Total Solar Eclipse Observations Of Hot Prominence Shrouds, Shadia Rifai Habbal, Miloslav Druckmüller, Huw Morgan, I. Scholl, V. Rusin, Adrian Daw, Judd Johnson, Martina B. Arndt

Physics Faculty Publications

Using observations of the corona taken during the total solar eclipses of 2006 March 29 and 2008 August 1 in broadband white light and in narrow bandpass filters centered at Fe x 637.4 nm, Fe xi 789.2 nm, Fe xiii 1074.7 nm, and Fe xiv 530.3 nm, we show that prominences observed off the solar limb are enshrouded in hot plasmas within twisted magnetic structures. These shrouds, which are commonly referred to as cavities in the literature, are clearly distinct from the overlying arch-like structures that form the base of streamers. The existence of these hot ...