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Search Publications by: Robert D. Shull (Assoc)

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Displaying 51 - 75 of 94

Structure and Magnetocaloric Properties of the Fe-Doped HoTiGe Alloy

April 20, 2006
Author(s)
Virgil Provenzano, B Baumgold, Robert D. Shull, Alexander J. Shapiro, Keiichi Koyama, Kazuo Watanabe, N K. Singh, K G. Suresh, A K. Nigam, S K. Malik
The structure and magnetocaloric properties of the Fe-doped HoTiGe compound were investigated by means of scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), x-ray diffraction (XRD), superconducting quantum interference device (SQUID)

Magnetic Fluids' Phase Transition Between Micelle and Mono-Dispersed Phases

April 18, 2006
Author(s)
S Taketomi, R V. Drew, Robert D. Shull
A very stably dispersed magnetic fluid (Mother MF) and its 1000-times diluted solution were independently zero-field-cooled from room temperature to 5 K followed by application of a magnetic field of 2.86 MA/m for 300 seconds. After the field was removed

Performance of Electret Ionization Chambers in Magnetic Field

April 7, 2006
Author(s)
P Kotrappa, L R. Stieff, Timothy F. Mengers, Robert McMichael, Robert D. Shull
Electret Ionization Chambers (EIC) are widely used for measuring radon and radiation. The radiation measured includes alpha, beta and gamma radiation. These detectors do not have any electronics and as such can be introduced into magnetic field regions. It

High Field X-Ray Diffraction Studies on Gd 5 (Ge 2-x Fe x )Si 2 (x = 0.05 and 0.2)

September 15, 2005
Author(s)
Jim L. Her, Keiichi Koyama, Kazuo Watanabe, Virgil Provenzano, F Fu, Robert D. Shull
We performed the X-ray diffraction measurements in magnetic fields up to 5 T for Gd5(Ge1.95Fe0.05)Si2 and Gd5(Ge1.8Fe0.2)Si2 which are noted recently as related materials for magnetic refrigerants. With heating from 8 K, the matrix of Gd5(Ge1.95Fe0.05)Si2

Details of the Sequential Steps in Magnetocaloric Regeneration

June 8, 2005
Author(s)
F Shir, Lawrence H. Bennett, Edward Della Torre, C Mavriplis, L Yanik, Robert D. Shull
We report on the first demonstration of the four sequential steps in magnetocaloric regeneration of a magnetocaloric material: magnetization, warm blow, demagnetization, and cold blow. The experimental results display temperature divergence due to

Antisymmetric Magnetoresistance in Magnetic Multilayers With Perpendicular Anisotropy

January 6, 2005
Author(s)
X M. Cheng, Sergei Urazhdin, T Tchernyshyov, C L. Chien, Valerian I. Nikitenko, Alexander J. Shapiro, Robert D. Shull
While magnetoresistance (MR) has generally been found to be symmetric in applied field H in non-magnetic or magnetic metals, we have observed antisymmetric MR in Co/Pt multilayers. Simultaneous domain imaging and transport measurements show that the

Modeling of Magnetization and Demagnetization in Magnetic Regenerative Refrigeration

July 2, 2004
Author(s)
F Shir, Edward Della Torre, Lawrence H. Bennett, C Mavriplis, Robert D. Shull
A time-dependent model of magnetization and demagnetization temperature profile is developed based on thermodynamic and heat transfer laws, material properties, and variable-field magnet parameters. Test results of a magnetic refrigeration test bed

Peak Magnetocaloric Effects in Al-Gd-Fe Alloys

June 1, 2004
Author(s)
Virgil Provenzano, Alexander J. Shapiro, T T. King, E R. Canavan, P Shirron, M J. DiPirro, Robert D. Shull
The magnetocaloric properties of several AlxGdyFez (with x+y+z=100) ternary alloys have been determined between 2-300 K. Three distinct peaks in the magnetic entropy change Sm vs T were found: a low temperature peak (near 10 K), an intermediate temperature

Anomalous Magnetic Aftereffect of a Frozen Magnetic Fluid

January 1, 2004
Author(s)
S Taketomi, R V. Drew, Robert D. Shull
A very stably dispersed magnetic fluid (MF) was zero-field-cooled from room temperature of 5 K followed by the application of a magnetic field of 2.86 MA/m for 300 seconds. After the field was removed (t = 0), its residual magnetization M was measured as a

Flux Loss Measurements of Ag- Sheathed Bi-2223 Tapes

January 1, 2004
Author(s)
Mi-Hye Jang, Winnie K. Wong-Ng, Robert D. Shull, Lawrence P. Cook, DeaSik Suh
Alternating current (AC) losses of two Bi-2223 ([Bi, Pb] : Sr : Ca : Cu :O = 2:2:2:3) tapes [one untwisted (Tape I, twist-pitch of mm) and the other with a twist-pitch of 8mm (Tape II)] were measured and compared. These samples, produced by the powder-in

Nucleation and Evolution of Hybrid Spin Spiral in Soft/Hard Ferromagnetic Bilayer

May 15, 2003
Author(s)
Yury P. Kabanov, V S. Gornakov, Valerian I. Nikitenko, Alexander J. Shapiro, Robert D. Shull
The hybrid exchange spring behavior in a bilayer consisting of an epitaxial film of Fe (500 A)/Smu2^}Co 7}(350 A) deposited onto a Cr(200 A) buffered MgO(110) substrate was investigated using the magneto-optical indicator film technique. Two critical

Room Temperature Active Regenerative Magnetic Refrigeration: Magnetic Nanocomposites

May 15, 2003
Author(s)
F Shir, L Yanik, Lawrence H. Bennett, Edward Della Torre, Robert D. Shull
Nanocomposites have several advantages as a refrigerant for 100 -300 K applications, compared to the other common methods of assembling a magnetic refrigeration bed, such as a layered arrangement of the thermal bed or mixing of different magnetic materials

Ru Spacer Thickness Dependences of the Domain Nucleation and Growth in Co/Ru/Co Synthetic Antiferromagnet

March 1, 2003
Author(s)
V S. Gornakov, Valerian I. Nikitenko, William F. Egelhoff Jr., Robert D. McMichael, Alexander J. Shapiro, Robert D. Shull
The relative orientation of Co magnetization vectors in a Co/Ru/Co/Ta structure vary gradually from parallel to antiparallel orientation as a function of Ru thickness varying from 0 nm to 1.0 nm. At intermediate average Ru thicknesses from 0.2 nm to 0.35

Enhanced Magnetocaloric Effects in R 3 (Ga 1-x Fe x ) 5 O 12 (R=Gd, Dy, Ho; 0

January 31, 2003
Author(s)
Virgil Provenzano, J Li, T T. King, E R. Canavan, P Shirron, M J. DiPirro, Robert D. Shull
A series of R 3(Ga1-xFex)5O12 (R=Gd, Dy, Ho; 0 3(Ga0.5Fe0.5)5O12 compound, which was reported in 1992 with possessing enhanced magnetocaloric effects, may be achieved by equilibrating at 1200 degrees C for 15 h, rather than at 900 degrees C for 15 h as it

Rotational Hysteresis of Exchange-Spring Magnets

September 13, 2002
Author(s)
J.S. Jiang, S D. Bader, H Kaper, G Leaf, Robert D. Shull, Alexander J. Shapiro, V S. Gornakov, Valerian I. Nikitenko, C L. Platt, A. E. Berkowitz, S David, E E. Fullerton
We highlight our experimental studies and micromagnetic simulations of the rotational hysteresis in exchange-spring magnets. Magneto-optical imaging and torque magnetometry measurements for SmCo/Fe exchange-spring films with uniaxial in-plane anisotropy