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

Physics Commons

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

Articles 1 - 19 of 19

Full-Text Articles in Physics

Morphological Transformations In The Magnetite Biomineralizing Protein Mms6 In Iron Solutions: A Small-Angle X‑Ray Scattering Study, Honghu Zhang, Xunpei Liu, Shuren Feng, Wenjie Wang, Klaus Schmidt-Rohr, Mufit Akinc, Marit Nilsen-Hamilton, David Vaknin, Surya K. Mallapragada Feb 2015

Morphological Transformations In The Magnetite Biomineralizing Protein Mms6 In Iron Solutions: A Small-Angle X‑Ray Scattering Study, Honghu Zhang, Xunpei Liu, Shuren Feng, Wenjie Wang, Klaus Schmidt-Rohr, Mufit Akinc, Marit Nilsen-Hamilton, David Vaknin, Surya K. Mallapragada

Chemical and Biological Engineering Publications

Magnetotactic bacteria that produce magnetic nanocrystals of uniform size and well-defined morphologies have inspired the use of biomineralization protein Mms6 to promote formation of uniform magnetic nanocrystals in vitro. Small angle X-ray scattering (SAXS) studies in physiological solutions reveal that Mms6 forms compact globular threedimensional (3D) micelles (approximately 10 nm in diameter) that are, to a large extent, independent of concentration. In the presence of iron ions in the solutions, the general micellar morphology is preserved, however, with associations among micelles that are induced by iron ions. Compared with Mms6, the m2Mms6 mutant (with the sequence of hydroxyl/carboxyl containing ...


Rhombohedral Magnetostriction In Dilute Iron (Co) Alloys, Nicholas J. Jones, Gabriela Petculescu, Marilyn Wun-Fogle, James B. Restorff, Arthur E. Clark, Kristi B. Hathaway, Deborah L. Schlagel, Thomas A. Lograsso Jan 2015

Rhombohedral Magnetostriction In Dilute Iron (Co) Alloys, Nicholas J. Jones, Gabriela Petculescu, Marilyn Wun-Fogle, James B. Restorff, Arthur E. Clark, Kristi B. Hathaway, Deborah L. Schlagel, Thomas A. Lograsso

Ames Laboratory Publications

Iron is a well-utilized material in structural and magnetic applications. This does not mean, however, that it is well understood, especially in the field of magnetostriction. In particular, the rhombohedral magnetostriction of iron, λ111 , is anomalous in two respects: it is negative in sign, in disagreement with the prediction of first principles theory, and its magnitude decreases with increasing temperature much too rapidly to be explained by a power law dependence on magnetization. These behaviors could arise from the location of the Fermi level, which leaves a small region of the majority 3d t2g states unfilled, possibly favoring small internal ...


Magneto-Structural Transformations Via A Solid-State Nudged Elastic Band Method: Application To Iron Under Pressure, Nikolai A. Zarkevich, Duane D. Johnson Jan 2015

Magneto-Structural Transformations Via A Solid-State Nudged Elastic Band Method: Application To Iron Under Pressure, Nikolai A. Zarkevich, Duane D. Johnson

Ames Laboratory Publications

We extend the solid-state nudged elastic band method to handle a non-conserved order parameter, in particular, magnetization, that couples to volume and leads to many observed effects in magnetic systems. We apply this formalism to the well-studied magneto-volumecollapse during the pressure-induced transformation in iron—from ferromagnetic body-centered cubic (bcc) austenite to hexagonal close-packed (hcp) martensite. We find a bcc-hcp equilibrium coexistence pressure of 8.4 GPa, with the transition-state enthalpy of 156 meV/Fe at this pressure. A discontinuity in magnetization and coherent stress occurs at the transition state, which has a form of a cusp on the potential-energy surface ...


Magnetic Interactions In Low-Dimensional Iron Nanostructures, Rui Zhang Jul 2013

Magnetic Interactions In Low-Dimensional Iron Nanostructures, Rui Zhang

Theses, Dissertations, and Student Research: Department of Physics and Astronomy

Three systems involving low-dimensional magnetic nanostructures, namely the Kondo Effect in Isolated Cu(Fe) Clusters, Magnetization Reversal in Transition-Metal/Fe:SiO2 Thin Films, and Anisotropy and Micromagnetism of Fe/CrPt Bilayers, have been investigated to understand the magnetic interactions in iron nanostructures.

Kondo Effect in Isolated Cu(Fe) Clusters —Iron impurities were added into copper clusters embedded in an insulating matrix to ensure that the Kondo effect is strictly confined by the size of the cluster. The Kondo temperature of our naoscale system is 0.7 K, which is greatly suppressed from its bulk value of 29 K and ...


Magnetic And Structural Transitions In The Iron-Chalcogenide High-Tc Superconductor: K0.8fe1.76se2.00, W. N. Rowan-Weetaluktuk, D. H. Ryan, J. M. Cadogan, R. Hu, Sergey L. Bud'ko, Paul C. Canfield Jan 2012

Magnetic And Structural Transitions In The Iron-Chalcogenide High-Tc Superconductor: K0.8fe1.76se2.00, W. N. Rowan-Weetaluktuk, D. H. Ryan, J. M. Cadogan, R. Hu, Sergey L. Bud'ko, Paul C. Canfield

Ames Laboratory Publications

57Fe Mössbauer spectroscopy was used to study single-crystals of K0.8Fe1.76Se2.00 from 6 K to 673 K. At 6 K, the hyperfine field (B hf) is canted away from the c-axis by 18 ± 3°. The temperature dependence of B hf follows a spin wavemodel with a spin excitation gap of 9 ± 1 meV. A sudden increase in the linewidth and a corresponding drop in (1/2)eQVzz at TN  = 532 K are indications of strong coupling between the magnetic and structural transitions.


Experimental Exploration Of The Origin Of Magnetostriction In Single Crystalline Iron, Qingfeng Xing, Thomas A. Lograsso, M. P. Ruffoni, C. Azimonte, S. Pascarelli, D. J. Miller Aug 2010

Experimental Exploration Of The Origin Of Magnetostriction In Single Crystalline Iron, Qingfeng Xing, Thomas A. Lograsso, M. P. Ruffoni, C. Azimonte, S. Pascarelli, D. J. Miller

Ames Laboratory Publications

The magnetostrictive atomic strain in a pure Fe single crystal was measured by differential x-ray absorption spectroscopy. The obtained tetragonal magnetostriction constant, (3/2)λ100, was determined to be 45 ppm, consistent with the previously reported theoretical value calculated from a spin-orbit coupling theory. These results provide a foundation for understanding the origin of magnetostriction in pure Fe as well as Fe-based binary alloys.


Fabrication And Magnetic Properties Of Fe Nanostructures In Anodic Alumina Membrane, J H. Lim, W S. Chae, H O. Lee, L Malkinski, S G. Min, J B. Wiley, J H. Jun, S H. Lee, J S. Jung Jan 2010

Fabrication And Magnetic Properties Of Fe Nanostructures In Anodic Alumina Membrane, J H. Lim, W S. Chae, H O. Lee, L Malkinski, S G. Min, J B. Wiley, J H. Jun, S H. Lee, J S. Jung

Physics Faculty Publications

Several Fe nanostructures with different lengths, diameters, and separations of the constituting magnetic components have been synthesized using anodized alumina membranes (AAMs) to understand the influence of these parameters on their magnetic properties. Fe nanostructures with high crystallinity and (110) orientation were synthesized by electrodeposition at room temperature in regular AAMs and mild-hard AAM (Mi-Ha AAM). Fe nanostructures with different aspect ratios (1:1, 1:10, and 1:75) in the form of nanodots, nanorods, or nanowires were synthesized in regular AAMs with the 100 nm interpore distance. Mi-Ha AAMs with two different pore sizes (70 and 120 nm) and ...


Arabidopsis Thaliana Glx2-1 Contains A Dinuclear Metal Binding Site, But Is Not A Glyoxalase 2, Pattraranee Limphong, Michael W. Crowder, Brian Bennett, Christopher A. Makaroff Jan 2009

Arabidopsis Thaliana Glx2-1 Contains A Dinuclear Metal Binding Site, But Is Not A Glyoxalase 2, Pattraranee Limphong, Michael W. Crowder, Brian Bennett, Christopher A. Makaroff

Physics Faculty Research and Publications

In an effort to probe the structure and function of a predicted mitochondrial glyoxalase 2, GLX2-1, from Arabidopsis thaliana, GLX2-1 was cloned, overexpressed, purified and characterized using metal analyses, kinetics, and UV–visible, EPR, and 1H-NMR spectroscopies. The purified enzyme was purple and contained substoichiometric amounts of iron and zinc; however, metal-binding studies reveal that GLX2-1 can bind nearly two equivalents of either iron or zinc and that the most stable analogue of GLX2-1 is the iron-containing form. UV–visible spectra of the purified enzyme suggest the presence of Fe(II) in the protein, but the Fe(II) can ...


The Effect Of Copt Crystallinity And Grain Texturing On Properties Of Exchange-Coupled Fe/Copt Systems, H. Oguchi, A. Zambano, M. Yu, Jason R. Hattrick-Simpers, D. Banerjee, Y. Liu, Z. L. Wang, J. P. Liu, S. E. Lofland, D. Josell, I. Takeuchi Jan 2009

The Effect Of Copt Crystallinity And Grain Texturing On Properties Of Exchange-Coupled Fe/Copt Systems, H. Oguchi, A. Zambano, M. Yu, Jason R. Hattrick-Simpers, D. Banerjee, Y. Liu, Z. L. Wang, J. P. Liu, S. E. Lofland, D. Josell, I. Takeuchi

Faculty Publications

The effect of the crystallinity and the grain texturing of CoPt hard layers on exchange coupled Fe/CoPt soft/hard magnetic systems was studied using gradient thickness multilayer thin films. We have studied the hard layer structures by transmission electron microscopy and x-ray diffraction, and characterized the exchange coupling interaction through magnetization loops obtained by the magneto-optical Kerr effect measurement. We found that exchange coupling strongly depends on the crystalline characteristics of the CoPt hard layer. There is correlation between the mixture of different grain orientations of the CoPt hard layer and coupling efficiency. In particular, interlayer coupling is enhanced ...


The Evolution Of Ga And As Core Levels In The Formation Of Fe/Gaas (001): A High Resolution Soft X-Ray Photoelectron Spectroscopic Study, Tiehan H. Shen, Denis Greig, Mark Hopkinson, George Daniel Waddill, Jamie D. W. Thompson, James R. Neal, Simon A. Morton, James G. Tobin, Jim A. D. Matthew Jul 2008

The Evolution Of Ga And As Core Levels In The Formation Of Fe/Gaas (001): A High Resolution Soft X-Ray Photoelectron Spectroscopic Study, Tiehan H. Shen, Denis Greig, Mark Hopkinson, George Daniel Waddill, Jamie D. W. Thompson, James R. Neal, Simon A. Morton, James G. Tobin, Jim A. D. Matthew

Physics Faculty Research & Creative Works

A high resolution soft x-ray photoelectron spectroscopic study of Ga and as 3d core levels has been conducted for Fe/GaAs (001) as a function of Fe thickness. This work has provided unambiguous evidence of substrate disrupting chemical reactions induced by the Fe overlayer—a quantitative analysis of the acquired spectra indicates significantly differing behavior of Ga and as during Fe growth, and our observations have been compared with existing theoretical models. Our results demonstrate that the outdiffusing Ga and as remain largely confined to the interface region, forming a thin intermixed layer. Whereas at low coverages Fe has little ...


Interphase Exchange Coupling In Fe/Sm-Co Bilayers With Gradient Fe Thickness, Ming-Hui Yu, Jason R. Hattrick-Simpers, Ichiro Takeuchi, Jing Li, Z. L. Wang, J. P. Liu, S. E. Lofland, Somdev Tyagi, J. W. Freeland, D. Giubertoni, M. Bersani, M. Anderle Jan 2005

Interphase Exchange Coupling In Fe/Sm-Co Bilayers With Gradient Fe Thickness, Ming-Hui Yu, Jason R. Hattrick-Simpers, Ichiro Takeuchi, Jing Li, Z. L. Wang, J. P. Liu, S. E. Lofland, Somdev Tyagi, J. W. Freeland, D. Giubertoni, M. Bersani, M. Anderle

Faculty Publications

We have fabricated Fe∕Sm–Co bilayers with gradient Fe thicknesses in order to systematically study the dependence of exchange coupling on the thickness of the Fe layer. The Fe layer was deposited at two different temperatures (150 and 300°C) to study the effect of deposition temperature on the exchange coupling. Magneto-optical Kerr effect and x-ray magnetic circular dichroism (XMCD) have been employed as nondestructive rapid characterization tools to map the magnetic properties of the gradient samples. Systematic enhancement in exchange coupling between the soft layer and the hard layer is observed as the soft layer thickness is decreased ...


Study Of Structural And Magnetic Properties Of Iron-Rich Mixed Rare-Earth Nddyfe (17-Y-X)Coxsiy Compounds, Kishore Kamaraju, Jinbo Yang, William B. Yelon, Oran Allan Pringle, M. S. Kim, Qingsheng Cai, William Joseph James Jan 2004

Study Of Structural And Magnetic Properties Of Iron-Rich Mixed Rare-Earth Nddyfe (17-Y-X)Coxsiy Compounds, Kishore Kamaraju, Jinbo Yang, William B. Yelon, Oran Allan Pringle, M. S. Kim, Qingsheng Cai, William Joseph James

Physics Faculty Research & Creative Works

A series of NdDyFe(17-y-x)CoxSiy solid solutions with = 2 and 3 and = 0.5 1.0 and 1.5 were prepared by induction melting stoichiometric amounts of high-purity elements. The postannealed samples consist of two phases belonging to the space groups R3 m and P63 mmc . The lattice parameters and the unit cell volumes were calculated from the refinements of the magnetic and structural unit cells using the FULLPROF version of the Rietveld program. For a fixed content of Co, the maximum Curie temperatures (305 C to 405 C) were observed in samples with = 1 and having two phases ...


On The Temperature Dependence Of Multiple- And Single-Scattering Contributions In Magnetic Exafs, H. Wende, F. Wilhelm, P. Poulopoulos, K. Baberschke, J. W. Freeland, Y. U. Idzerda, A. Rogalev, Deborah L. Schlagel, Thomas A. Lograsso, D. Arvanitis Sep 1999

On The Temperature Dependence Of Multiple- And Single-Scattering Contributions In Magnetic Exafs, H. Wende, F. Wilhelm, P. Poulopoulos, K. Baberschke, J. W. Freeland, Y. U. Idzerda, A. Rogalev, Deborah L. Schlagel, Thomas A. Lograsso, D. Arvanitis

Ames Laboratory Conference Papers, Posters, and Presentations

We demonstrate that the temperature dependence of structural as well as magnetic fluctuations can be probed by the use of the Magnetic Extended X-ray Absorption Fine Structure (MEXAFS) spectroscopy. We compare those to the dynamic disorder as probed by the EXAFS. Here we present temperature-dependent MEXAFS investigations carried out at the L-edges of a thin Fe film and a Gd single crystal. By comparing the experimental results to ab initio calculations the single-scattering contributions are separated from multiple-scattering contributions. It is found that the multiple-scattering contributions are enhanced for the MEXAFS compared to the normal EXAFS.


Core Loss Reduction In Electrical Steels Through Materials Processing, B. Verbrugge, David C. Jiles Apr 1999

Core Loss Reduction In Electrical Steels Through Materials Processing, B. Verbrugge, David C. Jiles

Electrical and Computer Engineering Publications

Research has been conducted into the effects of laser scribing on the core losses of soft magnetic materials. Various types of lamination steels for use in electric motors and transformers were studied including iron based alloys containing carbon,silicon,nickel, and cobalt. The results show that the change in core losses for carbon,nickel, and cobalt alloys was small for the scribing conditions examined, but core loss reductions of up to 18% were achieved with iron–silicon alloys.


The Magnetomechanical Effect In Electrolytic Iron, Michael K. Devine, David C. Jiles Apr 1996

The Magnetomechanical Effect In Electrolytic Iron, Michael K. Devine, David C. Jiles

Ames Laboratory Publications

The effect of stress on the magnetization of high purity iron has been studied systematically at different locations on the M,H plane corresponding to a variety of magnetic states of the material. The results confirm earlier studies that show the sign of the derivative dM/dσ changes at different locations on the M,H plane, and can even change as a result of a monotonic increase of stress either in compression or tension. The observed behavior can be explained on the basis of a recent theory which predicts that the irreversible changes in magnetization resulting from changes in ...


Hydrogen Charging In Nickel And Iron And Its Effect On Their Magnetic Properties, A. Ramesh, Madhav Rao Govindaraju, David C. Jiles, S. B. Biner, J. M. Roderick Apr 1996

Hydrogen Charging In Nickel And Iron And Its Effect On Their Magnetic Properties, A. Ramesh, Madhav Rao Govindaraju, David C. Jiles, S. B. Biner, J. M. Roderick

Materials Science and Engineering Publications

The current study was undertaken to explore the possibility of detecting hydrogen cavitation in magnetic materials through magnetic propertymeasurements. It is known that dissolved hydrogen in a material causes microvoids. These voids may affect the structure‐sensitive magnetic properties such as coercivity and remanence. In this study, hydrogen was introduced into nickel and iron by two processes, namely thermal charging and cathodic charging. The effect on the magnetic properties was measured. In addition, the variation of the magnetic properties with porosity was studied.


Importance Of Boundary Reflections In The Theory Of Diffusive Light Scattering, Douglas J. Durian Nov 1995

Importance Of Boundary Reflections In The Theory Of Diffusive Light Scattering, Douglas J. Durian

Department of Physics Papers

This PDF file contains the letter “Letter: Importance of boundary reflections in the theory of diffusive light scattering [see 33(12)3849-3852(Dec1994)]” for OE Vol. 34 Issue 11


Simultaneous Determination Of Fe 3p Spin-Orbit And Exchange Splittings In Photoemission, D. J. Huang, D. Mark Riffe, J. L. Erskine Jun 1995

Simultaneous Determination Of Fe 3p Spin-Orbit And Exchange Splittings In Photoemission, D. J. Huang, D. Mark Riffe, J. L. Erskine

All Physics Faculty Publications

Spin-resolved core-level photoemission data from the 3p level of ultrathin Fe films [1.4–5.1 monolayers (ML)] epitaxially grown on W(110) have been obtained. A nonlinear least-squares analysis, based on a one-particle Hamiltonian that simultaneously includes core-valence exchange and core-hole spin-orbit interactions, is developed. It is first tested on Fe 2p magnetic circular dichroism (MCD) photoemission spectra and shown to successfully describe the MCD asymmetry data. The model is then used to analyze our thin-film 3p data. With increasing film thickness the spin-orbit splitting (0.67±0.02 eV) remains constant (as expected), the exchange splitting increases from ...


A Masing [Fe Xi] Line, Gary J. Ferland Sep 1993

A Masing [Fe Xi] Line, Gary J. Ferland

Physics and Astronomy Faculty Publications

I draw attention to a maser which occurs within the ground term of Fe10+. In many photoionized environments, infrared fine-structure lines and the [O I] λ6300 line become optically thick but maser amplification of ionic fine-structure lines is unusual. During the course of development of a code designed to simulate gas under radiative-collisional equilibrium, the radiative transfer of roughly 500 ionic/atomic emission lines was treated using escape probabilities. Nearly all forbidden lines can become optically thick under extreme conditions, but the 3Pj = 1, 0 [Fe XI] 6.08 μm transition is the only line which ...