J. J. Rhyne

National Institute of Standards and Technology

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Hugh C. Wolfe

Childrens Cardiomyopathy Foundation

247

C. D. Graham

Centre de Mathématiques Appliquées

215

J. A. Borchers

NIST Center for Neutron Research

C. P. Flynn

University of Illinois Urbana-Champaign

C. D. Graham

South Puget Sound Community College

R. W. Erwin

NIST Center for Neutron Research

Christopher D. Graham

University of Strathclyde

M. B. Salamon

Los Alamos National Laboratory

G. E. Fish

Rao Research and Consulting (United States)

S. J. Pickart

University of Rhode Island

Cooperative Institutions

National Institute of Standards and Technology

Argonne National Laboratory

Centre National de la Recherche Scientifique

IBM (United States)

Massachusetts Institute of Technology

Oak Ridge National Laboratory

University of Illinois Urbana-Champaign

Nokia (United States)

Brookhaven National Laboratory

IBM Research - Thomas J. Watson Research Center

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Review of the Lujan neutron scattering center: basic energy sciences prereport February 2009

Alan J. Hurd J. J. Rhyne Paul Spurgeon Lewis

The Lujan Neutron Scattering Center (Lujan Center) at LANSCE is a designated National User Facility for neutron scattering and nuclear physics studies with pulsed beams of moderated neutrons (cold, thermal, and epithermal). As one of five experimental areas at the Los Alamos Neutron Science Center (LANSCE), the Lujan Center hosts engineers, scientists, and students from around the world. The Lujan Center consists of Experimental Room (ER) 1 (ERl) built by the Laboratory in 1977, ER2 built by the Office of Basic Energy Sciences (BES) in 1989, and the Office Building (622) also built by BES in 1989, along with a chem-bio lab, a shop, and other out-buildings. According to a 1996 Memorandum of Agreement (MOA) between the Defense Programs (DP) Office of the National Nuclear Security Agency (NNSA) and the Office of Science (SC, then the Office of Energy Research), the Lujan Center flight paths were transferred from DP to SC, including those in ERI. That MOA was updated in 2001. Under the MOA, NNSA-DP delivers neutron beam to the windows of the target crypt, outside of which BES becomes the 'landlord.' The leveraging nature of the Lujan Center on the LANSCE accelerator is a substantial annual leverage to themore » $11 M BES operating fund worth approximately $56 M operating cost of the linear accelerator (LINAC)-in beam delivery.« less

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Center (category theory)

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Magnetic Multilayers

Physica Scripta (1989)

J. J. Rhyne R. W. Erwin J. A. Borchers M. B. Salamon R. Du

Single crystal multilayer films with alternate heavy rare earth and yttrium layers have been shown by neutron diffraction to exhibit long-range magnetic order. Analysis of the neutron results on Dy|Y and Er|Y superlattices shows that the phase of the modulated magnetic structures in the Dy and Er is preserved across the intervening Y non-magnetic layers and corresponds to a "pseudo turn-angle" near 51 degrees in the Y, which is in accord with theoretical calculations from the band structure. This suggests that the exchange coupling is via a conduction band spin density wave in both Y and Dy, stabilized by the 4f spins of the Dy. The magnetic coherence length, determined from the neutron linewidth, exhibits a 1/r dependence on the Y layer thickness for a fixed number of Dy planes. The ferromagnetic transitions occurring in the pure elements are completely suppressed in the multilayers due to epitaxial "clamping" by the Y layers which exhibits the development of sufficient magnetostrictive strain to induce the phase transition. The temperature of the intermediate transitions in Er|Y multilayers is also modified by magnetostriction and evidence is found for different turn angles for c-axis and basal plane moment components.

Magnetic structure

10.1088/0031-8949/1989/t29/005

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Citations (7)

Magnetic structure of Dy-Y superlattices

Physical review. B, Condensed matter (1987)

R. W. Erwin J. J. Rhyne M. B. Salamon J. A. Borchers S.K. Sinha

Two samples of Dy-Y superlattices produced by molecular-beam-epitaxy techniques are shown by neutron diffraction to order magnetically in a helix which is incommensurate with the bilayer thickness. One sample consists of 64 bilayers, each bilayer made up of about 15 growth planes (42 A\r{}) of Dy atoms followed by 14 planes (38 A\r{}) of Y atoms. The second sample has 90 layers, each layer consisting of 9 Dy atomic planes and 8 ${\mathrm{Dy}}_{0.5}$${\mathrm{Y}}_{0.5}$ alloy planes. The phase coherence of this ordering extends over several bilayers, and is especially striking in the sample where the layers of localized Dy spins are separated by 14 atomic planes of nonmagnetic Y. The fact that the helix chirality propagates across several bilayers rules out a simple scalar Ruderman-Kittel-Kasuya-Yosida coupling between the Dy planes on either side of an Y layer, but suggests instead that a helical spin density wave is induced in the Y conduction electrons. A simple model for the superlattice structure factor demonstrates that observed asymmetries in the magnetic diffraction-peak intensities can be ascribed to the existence of different magnetic modulation wave vectors in each layer type (Dy and Y). In these superlattices the strain clamping by the intervening non-Dy layers and the substrate suppresses the first order ferromagnetic transition found in bulk Dy in both zero and finite fields. Although the planar magnetostriction is clamped, it is observed that the application of a magnetic field in the basal plane produces at low temperatures a second order irreversible transition to a metastable ferromagnetic state. At high temperature the magnetization process is initiated by a reduction of the helical coherence length due to a random-field coupling to the uncompensated Dy layer moment. This allows us to estimate the strength of the interaction through the Y layers.

Magnetic structure

10.1103/physrevb.35.6808

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Citations (174)

Ground state spin excitations in HoAl2

Journal of Applied Physics (1982)

J. J. Rhyne N. C. Koon

Inelastic neutron scattering has been used to examine the spin waves in a single crystal of the cubic Laves-phase compound HoAl2, which orders at a TC=28 K. Three pairs of acoustic (in-phase spin precession) and optic (out-of-phase precession) modes were observed in their respective Brillouin zones centered at (220) and (002). Due to the weak Ho–Ho exchange all modes show relatively little dispersion (e.g., the lowest acoustic mode which exhibits a band width of 1.5 meV and a q=0 gap of 1.4 meV). Measurements were made at 4 K for spin waves propagating in three directions [q,q,0], [q,0,0], and [q,q,q]. The spectra showed significant anisotropy in the second half of each zone. The observed inelastic scattering modes have been analyzed using an RPA pseudo-boson formalism with crystal field and exchange parameters consistent with those found for other RAl2 compounds.

Brillouin zone

Spin wave

10.1063/1.330362

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Magnetostriction of Dilute Dysprosium Iron and of Gadolinium Iron Garnets

Journal of Applied Physics (1968)

A. E. Clark J. J. Rhyne Earl R. Callen

λ γ,2 and λε,2 have been measured on a series of partially substituted DyxY1−xIG single crystals between 4.2° and 300°K and in fields up to 110 kOe. Because of the ground-state configuration of the Dy3+ ion (6H15/2) in the crystal field, DyIG has a large magnetostriction. However, since the exchange field on the rare-earth ion is small (Hex ≈ 300 kOe), this magnetostriction is large only at low temperatures. The 4.2°K magnetoelastic energies of the Dy3+ ion in the garnet are: Bγ,2 = λγ,2/2(C11–C12) = − 830 cm−1 and Bε,2 = λ111/4C44 = −1090 cm−1 which are in fact the same order of magnitude as the large energies observed in dysprosium metal. The magnetostriction is found to be linear in Dy concentration, establishing a single-ion source of the magnetostriction. Since the rare-earth exchange field is relatively small, the forced magnetostrictions are extraordinarily large and λ actually decreases from a large value to zero with increasing field strength whenever the iron moment dominates (x < 0.25). To understand these large and unusual temperature and field dependences, crystal-field effects, which affect λγ,2( = 32λ100) and λε,2( = 32λ111) differently, are essential. The magnetostriction in fully substituted GdIG at low temperatures has also been measured. Since the ground state of Gd3+ has zero orbital angular momentum, only a small magnetostriction is expected. This is indeed observed and the magnetostriction of GdIG is of the same magnitude as that of YIG. In particular, at 4.2°K, the contribution of Gd3+ to λγ,2 is 12×10−6, and to λε,2 is 1.8×10−6.

Dysprosium

10.1063/1.2163526

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Citations (35)

Spin and Orbital Susceptibility of Co Impurities

AIP conference proceedings (1973)

A. Ritter J. Bensel John A. Gardner Hugh C. Wolfe C. D. Graham

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation A. L. Ritter, J. Bensel, J. A. Gardner; Spin and Orbital Susceptibility of Co Impurities. AIP Conf. Proc. 1 January 1973; 10 (1): 1639–1643. https://doi.org/10.1063/1.2946869 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioAIP Conference Proceedings Search Advanced Search |Citation Search

10.1063/1.2946869

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Citations (2)

ANOMALOUS HALL EFFECT IN RARE EARTH METALS.

J. J. Rhyne R.S. Lee

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Magnetic structure in Dy/Sc superlattices

Carolina Digital Repository (University of North Carolina at Chapel Hill) (1993)

F. Tsui C. P. Flynn R. S. Beach J. A. Borchers R. W. Erwin

Magnetic structure

10.17615/t374-6y40

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Citations (1)

Spin excitations in [La1−xCaxMnO3] in the mixed-phase region

Journal of Applied Physics (2002)

L. Stumpe B. J. Kirby H. Kaiser J. J. Rhyne J. F. Mitchell

The magnetic excitations and the ferromagnetic order parameter have been studied by neutron scattering in a series of the manganese-based CMR perovskites [La1−xCaxMnO3] (x=0.46, 0.48, 0.50) near the metallic ferromagnetic to insulating antiferromagnetic phase. Well-defined ferromagnetic spin waves were detected for the x=0.46 and x=0.48 compositions. From the measurements of the order parameter, only the x=0.48 sample showed conclusive evidence of a coexistence of an antiferromagnetic phase with the ferromagnetic phase. For this composition, hysteresis was observed in the spin wave intensity but not in the spin stiffness parameter. This effect indicates that the ferromagnetic exchange is not perturbed by the antiferromagnetic ordering. No measurable ferromagnetic magnetization was found in the x=0.50 sample; thus no spin waves could be detected. The results indicate that the onset of the antiferromagnetism upon hole doping for the series occurs in a narrow region of x below the x=0.50 phase boundary.

Spin wave

Phase boundary

10.1063/1.1448307

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Citations (2)

Transition Metal Alloys — A Chemist's View

AIP conference proceedings (1973)

Leo Brewer Hugh C. Wolfe C. D. Graham J. J. Rhyne

The valence‐bond model, so widely used in chemistry, is equally applicable to transition metal alloys. In contrast to models commonly used by physicists, this model emphasizes the distribution of electrons in real space and the differences in spatial distribution of f and d electrons in contrast to s and p electrons. From the energies of the different electronic configurations that are known for almost all of the gaseous atoms and bonding energies for different types of electrons, one can calculate the energies of the electronic configurations in the metal. Thus Ba, Ta, and W with gaseous ground states s2, d3s2, and d4s2 are calculated to have the predominant configurations ds, d4s, and d5s, respectively, in the metal. The determination of the correct electronic configuration in the metal is the keystone to reliable predictions. The bonding energies due to the different types of electrons can be used to readily evaluate thermodynamic data to predict the stable composition range for a given structure, or the crystal structure that is stable at a given composition and temperature, and the effect of pressure, temperature and alloying upon the relative stabilities of different structures as well as the occurrence of magnetism.

Chemist

10.1063/1.2946889

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Citations (3)