Open Access. Powered by Scholars. Published by Universities.®
Materials Science and Engineering
Materials Research Science and Engineering Center: Faculty Publications
- Keyword
-
- Permanent magnet (2)
- Anisotropy (1)
- Coercive force (1)
- Coercivity (1)
- Discrete domain-wall pinning (1)
-
- Exchange-coupling (1)
- FePt (1)
- FePt thin films (1)
- Grain refinement (1)
- Granular films (1)
- High anisotropy (1)
- L10 (1)
- L10structure (1)
- Magnetic anisotropy (1)
- Magnetic films (1)
- Magnetic recording (1)
- Micromagnetic simulations (1)
- Nanocluster (1)
- Permanent magnets (1)
- R2Fe14B –Fe nanocomposite (1)
- Rapid solidification (1)
- Remanence enhancement (1)
- Samarium alloys. (1)
- Samarium–cobalt films (1)
- SmCo alloys (1)
- Thermal stability (1)
Articles 1 - 13 of 13
Full-Text Articles in Engineering
Oscillatory Interlayer Exchange Coupling In [Pt/Co]N/Nio/[Co/Pt]N Multilayers With Perpendicular Anisotropy: Dependence On Nio And Pt Layer Thicknesses, Z. Y. Liu, Lanping Yue, D. J. Keavney, Shireen Adenwalla
Oscillatory Interlayer Exchange Coupling In [Pt/Co]N/Nio/[Co/Pt]N Multilayers With Perpendicular Anisotropy: Dependence On Nio And Pt Layer Thicknesses, Z. Y. Liu, Lanping Yue, D. J. Keavney, Shireen Adenwalla
Materials Research Science and Engineering Center: Faculty Publications
Interlayer exchange coupling has been studied in a series of [Pt( tPt Å)/Co(4 Å)]n/NiO( tNiO)/[Co(4 Å)/Pt( tPt Å)]n multilayers with perpendicular anisotropy. The coupling oscillates between antiferromagnetic and ferromagnetic as a function of tNiO with a period of ~5 Å, and the oscillatory behavior is related to the antiferromagnetic ordering of the NiO layer. This interlayer coupling between two Co/Pt multilayers is shown to occur domain by domain by magnetic force microscopy imaging. For the strongest antiferromagnetic coupling at tNiO = 11 Å, an oscillation with a period of ~6 Å is superposed …
Quantum Entanglement Of Anisotropic Magnetic Nanodots, Ralph Skomski, Andrei Y. Istomin, Anthony F. Starace, David J. Sellmyer
Quantum Entanglement Of Anisotropic Magnetic Nanodots, Ralph Skomski, Andrei Y. Istomin, Anthony F. Starace, David J. Sellmyer
Materials Research Science and Engineering Center: Faculty Publications
Anisotropic magnetic nanodots are promising physical realizations of qubits for quantum computing at finite temperature owing to their well-separated low-lying energy levels and scalability. The entanglement of two interacting magnetic nanodots is investigated and shown both analytically and numerically to be resonantly dependent on their interaction strength and on differences in their properties. These results provide criteria for fabricating and coupling magnetic nanodots so that their low-lying eigenstates can be significantly entangled.
Disorder-Induced Depression Of The Curie Temperature In Mechanically Milled Gdal2, Marco Morales Torres, D. S. Williams, Paul M. Shand, C. Stark, Thomas M. Pekarek, Lanping Yue, Valeri G. Petkov, Diandra Leslie-Pelecky
Disorder-Induced Depression Of The Curie Temperature In Mechanically Milled Gdal2, Marco Morales Torres, D. S. Williams, Paul M. Shand, C. Stark, Thomas M. Pekarek, Lanping Yue, Valeri G. Petkov, Diandra Leslie-Pelecky
Materials Research Science and Engineering Center: Faculty Publications
The effect of disorder on the ferromagnetic transition is investigated in mechanically milled GdAl2. GdAl2is a ferromagnet when crystalline and a spin glass when amorphous. Mechanical milling progressively disorders the alloy, allowing observation of the change from ferromagnetic to a disordered magnetic state. X-ray diffraction and pair-distribution-function analysis are used to determine the grain size, lattice parameter, and mean-squared atomic displacements. The magnetization as a function of temperature is described by a Gaussian distribution of Curie temperatures. The mean Curie temperature decreases with decreasing lattice parameter, where lattice parameter serves as a measure of defect concentration. …
First-Principles Study Of Adsorption Of Methanethiol On Co(0001), Ligen Wang, Evgeny Y. Tsymbal, Sitaram Jaswal
First-Principles Study Of Adsorption Of Methanethiol On Co(0001), Ligen Wang, Evgeny Y. Tsymbal, Sitaram Jaswal
Materials Research Science and Engineering Center: Faculty Publications
Investigation of the resident site and the adsorption phase structure of thiolates is of fundamental importance for understanding the formation of self-assembled organic monolayers on metal substrate surfaces. In the present study, we have investigated adsorption of methanethiol, CH3SH, on the ferromagnetic Co (0001) surface using density functional theory calculations.We find that the dissociative adsorption of CH3SH forming an adsorbed methylthiolate (CH3S) and an adsorbed H atom is energetically favorable, and that the CH3S molecule adsorbed at the threefold fcc and hcp hollow sites is most stable. The adsorption energy at the …
Field-Controlled Domain-Wall Resistance In Magnetic Nanojunctions, John D. Burton, Arti Kashyap, Mikhail Ye. Zhuravlev, Ralph Skomski, Evgeny Y. Tsymbal, Sitaram Jaswal, O.N. Mryasov, R.W. Chantrell
Field-Controlled Domain-Wall Resistance In Magnetic Nanojunctions, John D. Burton, Arti Kashyap, Mikhail Ye. Zhuravlev, Ralph Skomski, Evgeny Y. Tsymbal, Sitaram Jaswal, O.N. Mryasov, R.W. Chantrell
Materials Research Science and Engineering Center: Faculty Publications
The electrical resistance of a constrained domain wall in a nanojunction is investigated using micromagnetic modeling and ballistic conductance calculations. The nanojunction represents two ferromagnetic electrodes connected by a ferromagnetic wire of 10 nm in length and of a few nanometers in cross section. We find that the anisotropy of the electrodes favors a localization of the domain wall within the constriction (wire) revealing a positive domain-wall resistance. An applied magnetic field moves the domain wall toward one of the electrodes and reduces its width. This compression of the domain wall leads to a sizeable enhancement of the domain-wall resistance.
L10 Ordered Fept:C Composite Films With (001) Texture, M. L. Yan, Renat F. Sabiryanov, Yinfan Xu, Xingzhong Li, David J. Sellmyer
L10 Ordered Fept:C Composite Films With (001) Texture, M. L. Yan, Renat F. Sabiryanov, Yinfan Xu, Xingzhong Li, David J. Sellmyer
Materials Research Science and Engineering Center: Faculty Publications
Highly textured (001) FePt:C nanocomposite thin films, deposited directly on thermally oxidized Si wafers, are obtained by multilayer deposition plus subsequent thermal annealing. Nanostructures, crystalline orientations, interactions, and magnetic properties are investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), magnetic force microscopy, and magnetic measurements. The formation of the ordered L10 phase is confirmed by XRD, and only visible (00 ) peaks indicate a high degree of the (001) texture. TEM observation reveals that FePt grains are embedded in the C matrix and appear to be well isolated.
Nanostructure And Magnetic Properties Of Fept :C Cluster Films, Yinfan Xu, M. L. Yan, David J. Sellmyer
Nanostructure And Magnetic Properties Of Fept :C Cluster Films, Yinfan Xu, M. L. Yan, David J. Sellmyer
Materials Research Science and Engineering Center: Faculty Publications
Magnetic properties and nanostructure of FePt : C cluster-deposited films with C volume fraction of 7%, 14%, 33%, and 45% have been studied. As-deposited FePt : C films were prepared by a multilayer method in which FePt layers were deposited from a cluster source employing a gas-aggregation technique and C layers from a normal sputtering gun. In the as-deposited films, FePt clusters with fcc structure are embedded in the C matrix. The high anisotropy FePt L10 cluster structure was realized in the films via post-deposition annealing and the nanostructure of the films was observed by high-resolution transmission electron microscope …
The Effect Of Transition Metal Additions On The Microstructure And Properties Of Nanocomposite Pr–Fe–B Permanent Magnets, Jeffrey E. Shield, Yi Liu, R. Marr, Z. Chen, Baomin Ma
The Effect Of Transition Metal Additions On The Microstructure And Properties Of Nanocomposite Pr–Fe–B Permanent Magnets, Jeffrey E. Shield, Yi Liu, R. Marr, Z. Chen, Baomin Ma
Materials Research Science and Engineering Center: Faculty Publications
Permanent magnets with the general composition Pr9 (Fe0.95Co0.05)85.5M0.5B5, where M denotes a transition metal, have been produced by melt spinning. The effect on the microstructure and magnetic properties of eight different alloying elements has been examined. The grain size and distribution have been correlated to the maximum energy product obtained. The grain size of the Pr9 (Fe0.95Co0.05) 85.5B5 control alloy was determined to be 17.5 nm, and it was found that the grain size was not significantly reduced compared to the control …
Magnetization Reversal And Giant Coercivity In Sm-Co/Cu-Ti Particulate Films, Jian Zhou, Arti Kashyap, Yi Liu, Ralph Skomski, David J. Sellmyer
Magnetization Reversal And Giant Coercivity In Sm-Co/Cu-Ti Particulate Films, Jian Zhou, Arti Kashyap, Yi Liu, Ralph Skomski, David J. Sellmyer
Materials Research Science and Engineering Center: Faculty Publications
Highly coercive granular SmCo/CuTi films were produced by thermal processing of sputtered SmCo5 (CuTi) multilayers and investigated experimentally and theoretically. Electron microscopy shows that the processed films consist of spherical grains that have diameters of 5–10 nm and are embedded in a matrix. Both the grains and the matrix phase exhibit the CaCu5 structure, but the matrix is probably Cu-rich. The films have high coercivities of up to 50.4 kOe at 300 K. Analytical calculations and micromagnetic simulations yield a transition from a nucleation-type weak-interaction regime to a discrete-pinning-type strong-interaction regime. The transition occurs at packing fractions similar …
Domain-Wall Pinning At Inhomogenities Of Arbitrary Cross-Sectional Geometry, Ralph Skomski, Jian Zhou, Arti Kashyap, David J. Sellmyer
Domain-Wall Pinning At Inhomogenities Of Arbitrary Cross-Sectional Geometry, Ralph Skomski, Jian Zhou, Arti Kashyap, David J. Sellmyer
Materials Research Science and Engineering Center: Faculty Publications
Abstract—The coercivity of cellular Sm-Co based permanent magnets is investigated by model calculations. The grain boundaries responsible for the pinning coercivity are modeled as planar inhomogenities with arbitrary cross-sectional geometry. The calculation yields a physically transparent integral equation for the pinning energy, whose derivative is the pinning force. The theory rationalizes experimental data on a semiquantitative level, but without adjustable parameters, and bridges the gap between smooth concentration gradients and abrupt interfaces. Explicit results are obtained for sinoidal profiles, for very thin grain boundaries, and for profiles intermediate between attractive and repulsive pinning. The corrections predicted by the present model …
Magnetization Processes In Melt-Spun Sm-Co-Based Alloys With The Tbcu7-Type Structure, A. Hsiaoa, S. Aich, L. H. Lewis, Jeffrey E. Shield
Magnetization Processes In Melt-Spun Sm-Co-Based Alloys With The Tbcu7-Type Structure, A. Hsiaoa, S. Aich, L. H. Lewis, Jeffrey E. Shield
Materials Research Science and Engineering Center: Faculty Publications
The initial magnetization processes in melt-spun Sm-Co alloys with remanent ratios above 0.7 have been studied. Alloys of (Sm(1/(6+x) Co (5+x)/(6+x) ) 94Nb3C3 (x = 067, 1.7, 2.3 and 3) alloys modified with Nb and C were melt spun at wheel speeds of 20 and 40 m/s, and the compositions span the range between the Sm2Co17 and SmCo5 stoichiometries. Structurally, all alloys formed in the TbCu7-type structure, although a small amount of Sm2Co7 was observed in Sm-rich samples, and a small amount of fcc Co formed …
Exchange Model For Oscillatory Interlayer Coupling And Induced Unidirectional Anisotropy In [Pt/Co]3/Nio/[Pt/Co]3 Multilayers, Mikhail Ye Zhuravlev, Evgeny Y. Tsymbal, Sitaram Jaswal
Exchange Model For Oscillatory Interlayer Coupling And Induced Unidirectional Anisotropy In [Pt/Co]3/Nio/[Pt/Co]3 Multilayers, Mikhail Ye Zhuravlev, Evgeny Y. Tsymbal, Sitaram Jaswal
Materials Research Science and Engineering Center: Faculty Publications
In a recent Letter [1] Liu and Adenwalla found an interesting oscillatory behavior of the interlayer exchange coupling (IEC) through an insulating NiO (111) layer with a period of 2 monolayers (ML). They interpreted this phenomenon in terms of multiple reflections of electronic waves from a periodic atomic potential in the spirit of the model of Ref. [2]. However, this interpretation is not consistent with the tunneling mechanism used by the authors which would result in a modulated exponential decrease of the IEC but no periodic change in sign. In this Comment we show that the observed oscillatory IEC can …
Effect Of Interface Bonding On Spin-Dependent Tunneling From The Oxidized Co Surface, Kirill D. Belashchenko, Evgeny Y. Tsymbal, Mark Van Schilfgaarde, Derek A. Stewart, Ivan I. Oleynik, Sitaram Jaswal
Effect Of Interface Bonding On Spin-Dependent Tunneling From The Oxidized Co Surface, Kirill D. Belashchenko, Evgeny Y. Tsymbal, Mark Van Schilfgaarde, Derek A. Stewart, Ivan I. Oleynik, Sitaram Jaswal
Materials Research Science and Engineering Center: Faculty Publications
We demonstrate that the factorization of the tunneling transmission into the product of two surface transmission functions and a vacuum decay factor allows one to generalize Jullière's formula and explain the meaning of the "tunneling density of states" in some limiting cases. Using this factorization we calculate spin-dependent tunneling from clean and oxidized fcc Co surfaces through vacuum into Al using the principal-layer Green's-function approach. We demonstrate that a monolayer of oxygen on the Co(111) surface creates a spin-filter effect due to the Co-O bonding which produces an additional tunneling barrier in the minority-spin channel. This changes the minority-spin dominated …