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Articles 1 - 12 of 12
Full-Text Articles in Physics
Effect On Focusing Fields By Ferromagnetic Cell Cores In Linear Induction Accelerators, Cooper Guillaume
Effect On Focusing Fields By Ferromagnetic Cell Cores In Linear Induction Accelerators, Cooper Guillaume
Senior Honors Theses
In the Los Alamos National Laboratories DARHT facility, there are two perpendicular linear induction accelerators, LIAs. The LIAs’ solenoids produce magnetic fields which focus the electron beam. Simultaneously, the accelerating pulse creates a magnetic field. These two field intensities act upon a ferromagnetic material in the cells to enhance magnetic flux density. Due to the nonlinearity of the material, this flux density will reach a saturation point. In turn, the magnetic field intensity of the axial solenoidal magnetic field will be affected and slightly altered. The width of the electron beam will increase, causing a decrease in effectiveness. Through simulation, …
The Influence Of A Surface On Hysteresis Loops For Single-Domain Ferromagnetic Nanoparticles, Saad Alsari
The Influence Of A Surface On Hysteresis Loops For Single-Domain Ferromagnetic Nanoparticles, Saad Alsari
Browse all Theses and Dissertations
The influence of surface effects on a hysteresis loop for single domain, ferromagnetic nanoparticles was examined. Theoretical equations were derived to describe the magnetic behavior of the domains and a MATLAB program was used to solve them. M-H curves were calculated for the case when a magnetic field is applied in the favorable magnetization direction (easy axis). In contrast, the calculations show there were no hysteresis loops when the magnetic field was applied perpendicular to the easy axis. Our studies showed how parameters of the surface such as a associated with saturation magnetization near the surface of nanoparticles and Ks …
Class Of Ferromagnetic Semiconductors, Larysa Shlyk, Sergiy A. Kryukov, Lance E. De Long, Barbara Schüpp-Niewa, Rainer Niewa
Class Of Ferromagnetic Semiconductors, Larysa Shlyk, Sergiy A. Kryukov, Lance E. De Long, Barbara Schüpp-Niewa, Rainer Niewa
Physics and Astronomy Faculty Patents
Single crystal and polycrystal oxoruthenates having the generalized compositions (Baz,Sr1−z)FexCoyRu6−(x+y)O11 (1≦(x+y)≦5; 0≦z≦1) and (Ba,Sr)M2±xRu4∓xO11 (M=Fe,Co) belong to a novel class of ferromagnetic semiconductors with applications in spin-based field effect transistors, spin-based light emitting diodes, and magnetic random access memories.
Superspin Glass Behaviour Of Interacting Ferromagnetic Nanoparticles In Discontinuous Magnetic Multilayers, Christian Binek
Superspin Glass Behaviour Of Interacting Ferromagnetic Nanoparticles In Discontinuous Magnetic Multilayers, Christian Binek
Christian Binek
Discontinuous magnetic multilayers [Co80Fe20(t)/Al2O3(3nm)]10 with t = 0.9 and 1.0nm are studied by SQUID magnetometry and ac susceptibility. Owing to dipolar interaction the superparamagnetic cluster systems undergo collective glass-like freezing upon cooling. While both samples exhibit very similar glass temperatures Tg » 45 K and critical exponents zn » 10 and g » 1.4 as obtained from the temperature dependencies of the relaxation time, t, and the nonlinear susceptibility, c3, dynamical scaling reveals different critical exponents, b(0.9nm) »1.0 and b(1.0nm) » 0.6, respectively.
Temperature Dependence Of The Training Effect In Exchange Coupled Ferromagnetic Bilayers, Christian Binek, Srinivas Polisetty, Sarbeswar Sahoo
Temperature Dependence Of The Training Effect In Exchange Coupled Ferromagnetic Bilayers, Christian Binek, Srinivas Polisetty, Sarbeswar Sahoo
Christian Binek
The temperature dependence of the training effect is studied in an exchange coupled thin-film bilayer composed of a hard ferromagnetic pinning (CoPtCrB) layer in proximity of a soft ferromagnetic pinned (CoCr) layer. Interlayer exchange shifts the hysteresis loops of the soft layer along the magnetic-field axis. This shift is quantified by the bias field in far reaching analogy to the exchange bias field of conventional antiferromagnetic/ferromagnetic heterostructures. A ferromagnetic domain state induced in the hard layer experiences aging very similar to the training behavior of the antiferromagnetic domain state in conventional exchange bias systems. Training originates from changes in the …
Radio-Frequency Heating Of Magnetic Nanoparticles, Mohammud Zafrullah Jagoo
Radio-Frequency Heating Of Magnetic Nanoparticles, Mohammud Zafrullah Jagoo
Browse all Theses and Dissertations
In the present study, a power supply capable of converting a direct current into an alternating current was built. The frequency of oscillation of the output current could be varied from 174.8 kHz to 726.0 kHz by setting a set of capacitors in resonance. To this power supply is attached a 20-turns copper coil in the shape of a spiral. Because of the high heat generated in the coil, the latter has to be permanently water-cooled. A vacuum pump removes the air between the sample holder and the coil. A fiber optic temperature sensor with an accuracy of 0.001 K …
Temperature Dependence Of The Training Effect In Exchange Coupled Ferromagnetic Bilayers, Christian Binek, Srinivas Polisetty, Sarbeswar Sahoo
Temperature Dependence Of The Training Effect In Exchange Coupled Ferromagnetic Bilayers, Christian Binek, Srinivas Polisetty, Sarbeswar Sahoo
Christian Binek Publications
The temperature dependence of the training effect is studied in an exchange coupled thin-film bilayer composed of a hard ferromagnetic pinning (CoPtCrB) layer in proximity of a soft ferromagnetic pinned (CoCr) layer. Interlayer exchange shifts the hysteresis loops of the soft layer along the magnetic-field axis. This shift is quantified by the bias field in far reaching analogy to the exchange bias field of conventional antiferromagnetic/ferromagnetic heterostructures. A ferromagnetic domain state induced in the hard layer experiences aging very similar to the training behavior of the antiferromagnetic domain state in conventional exchange bias systems. Training originates from changes in the …
Effect Of Tip Resonances On Tunnelling Anisotropic Magnetoresistance In Ferromagnetic Break Junctions: A First-Principles Study, John D. Burton, Renat F. Sabirianov, Julian P. Velev, O. N. Mryasov, Evgeny Y. Tsymbal
Effect Of Tip Resonances On Tunnelling Anisotropic Magnetoresistance In Ferromagnetic Break Junctions: A First-Principles Study, John D. Burton, Renat F. Sabirianov, Julian P. Velev, O. N. Mryasov, Evgeny Y. Tsymbal
Materials Research Science and Engineering Center: Faculty Publications
First-principles calculations of electron tunneling transport in nanoscale Ni and Co break-junctions reveal strong dependence of the conductance on the magnetization direction, an effect known as tunneling anisotropic magnetoresistance TAMR. An important aspect of this phenomenon stems from resonant states localized in the electrodes near the junction break. The energy and broadening of these states is strongly affected by the magnetization orientation due to spin-orbit coupling, causing TAMR to be sensitive to bias voltage on a scale of a few millivolts. Our results bear a resemblance to recent experimental data and suggest that TAMR driven by resonant states is a …
Domain-Wall Magnetoresistance Of Co Nanowires, Renat F. Sabirianov, Ashok K. Solanki, J. D. Burton, Sitaram S. Jaswal, Evgeny Y. Tsymbal
Domain-Wall Magnetoresistance Of Co Nanowires, Renat F. Sabirianov, Ashok K. Solanki, J. D. Burton, Sitaram S. Jaswal, Evgeny Y. Tsymbal
Physics Faculty Publications
Using density functional theory implemented within a tight-binding linear muffin-tin orbital method we perform calculations of electronic, magnetic, and transport properties of ferromagnetic free-standing fcc Co wires with diameters up to 1.5 nm. We show that finite-size effects play an important role in these nanowires resulting in oscillatory behavior of electronic charge and the magnetization as a function of the wire thickness, and a nonmonotonic behavior of spin-dependent quantized conductance. We calculate the magnetoresistance (MR) of a domain wall (DW) modeled by a spin-spiral region of finite width sandwiched between two semi-infinite Co wire leads. We find that the DW …
Superspin Glass Behaviour Of Interacting Ferromagnetic Nanoparticles In Discontinuous Magnetic Multilayers, Christian Binek
Superspin Glass Behaviour Of Interacting Ferromagnetic Nanoparticles In Discontinuous Magnetic Multilayers, Christian Binek
Christian Binek Publications
Discontinuous magnetic multilayers [Co80Fe20(t)/Al2O3(3nm)]10 with t = 0.9 and 1.0nm are studied by SQUID magnetometry and ac susceptibility. Owing to dipolar interaction the superparamagnetic cluster systems undergo collective glass-like freezing upon cooling. While both samples exhibit very similar glass temperatures Tg » 45 K and critical exponents zn » 10 and g » 1.4 as obtained from the temperature dependencies of the relaxation time, t, and the nonlinear susceptibility, c3, dynamical scaling reveals different critical exponents, b(0.9nm) »1.0 and b(1.0nm) » 0.6, respectively.
Optical And Magneto-Optical Properties Of Mnpt3 Films (Abstract), Segate Corporation, Pittsburgh, Pa, J. N. Hilfiker, Renat F. Sabirianov, Sitaram S. Jaswal, Roger D. Kirby, John A. Woollam
Optical And Magneto-Optical Properties Of Mnpt3 Films (Abstract), Segate Corporation, Pittsburgh, Pa, J. N. Hilfiker, Renat F. Sabirianov, Sitaram S. Jaswal, Roger D. Kirby, John A. Woollam
Physics Faculty Publications
Optically thick films of MnPt3 were prepared by magnetron sputtering onto quartz substrates. Postdeposition annealing at 850 °C resulted in highly textured (111) films with the L12 (Cu3Au) structure. MnPt3 films are ferromagnetic with a Curie temperature of 380 °C, and they show large magneto-optical effects in the visible.1,2 These films also show a high degree of long-range order. The diagonal components of the dielectric tensor were determined using variable angle spectroscopic ellipsometry measurements over the spectral range 1.2–2.4 eV. Magneto-optic Kerr rotation and ellipticity measurements were made at near normal incidence over the …
A Method For Measuring Magnetization To High Pressures, C. R. Johansen, Mark H. Nelson, J. H. Gardner
A Method For Measuring Magnetization To High Pressures, C. R. Johansen, Mark H. Nelson, J. H. Gardner
Faculty Publications
A partially successful attempt has been made to measure the magnetic moment per unit volume of ferromagnetic materials as a function of pressure to the 100-kbar region. The apparatus, an early version of which has been described previously, consists basically of two opposed Bridgman flat anvils of alumina. One anvil also acts as a dielectric-filled microwave resonant cavity for an x-band spectrometer, allowing electron spin resonance studies to be made to high pressure. The sample to be studied is placed in contact with the anvil-cavity and covered with a pressure-transmitting medium which in turn is encircled by a flat pyrophyllite …