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Magnetic Properties of Metal(II) Schiff Base Complexes

Description: Ligands prepared from various combinations of aldehydes and ketones with the appropriate aminealcohol were complexed with cupric acetate monohydrate. The complexes with O,NO or N,N,O donor atoms were synthesized to study the influences of the ligand on molecular structure, spin-spin interaction, and on the value of the exchange integral. The magnetic data indicated that of the eight Cu(II) complexes discussed, two behaved differently from known analogous compounds. Cu (benzoylacetone :ethanolamine) was compared to Cu(acac:ethanolamine), and Cu(pyrr:oaminophenol) was compared to Cu(acac:o-aminophenol). Each pair of complexes was postulated to have the same molecular structure. The synthesis and characterization of Mn(pyrr:oaminophenol) 2H2 is also discussed. The following physical data were collected and discussed: elemental analysis, melting point, molecular weight, infrared spectra, electronic spectra, and magnetic susceptibility.
Date: May 1976
Creator: Hines, Mary Katherine
Partner: UNT Libraries

MINOS Detector Steel Magnetic Measurements

Description: Magnetic measurements were made on one steel plate of the MINOS far detector. The conventionally used technique of measuring sense coil voltage induced by step changes in excitation current voltage was successful in providing stable, repeatable measurements. Measurements were made at several locations on the steel and the results are presented.
Date: March 3, 1999
Creator: Jaskierny, Robert C. Trendler and Walter F.
Partner: UNT Libraries Government Documents Department

MINOS test toroid magnetic measurements

Description: Magnetic measurements were made on a test ring constructed from the same steel used on the prototype MINOS far detector plate located in NMS. The conventionally used technique of measuring sense coil voltage induced by step changes in excitation current voltage was successful in providing stable, repeatable measurements. Measurements were made at several locations on the steel and the results are presented.
Date: March 3, 1999
Creator: Jaskierny, Robert C. Trendler and Walter F.
Partner: UNT Libraries Government Documents Department

Alignment of the VISA Undulator

Description: The Visible-Infrared SASE Amplifier (VISA) undulator consists of four 99cm long segments. Each undulator segment is set up on a pulsed-wire bench, to characterize the magnetic properties and to locate the magnetic axis of the FODO array. Subsequently, the location of the magnetic axis, as defined by the wire, is referenced to tooling balls on each magnet segment by means of a straightness interferometer. After installation in the vacuum chamber, the four magnet segments are aligned with respect to themselves and globally to the beam line reference laser. A specially designed alignment fixture is used to mount one straightness interferometer each in the horizontal and vertical plane of the beam. The goal of these procedures is to keep the combined rms trajectory error, due to magnetic and alignment errors, to 50{micro}m.
Date: April 15, 1999
Creator: Ruland, Robert
Partner: UNT Libraries Government Documents Department

Lattice disorder and magnetism in f-electron intermetallics

Description: Real materials can have real differences compared to ideal systems. For instance, non-Fermi liquid (NFL) behavior was initially thought to be due to chemical disorder, since the first such materials were all substituted. Although several nominally well-ordered NFL's have been discovered and extensively studied, the effect of disorder on the magnetic properties of f-electron intermetallic systems remains poorly understood. Disorder in NFL systems is reviewed from an experimental, local structure point of view, including a discussion of results on the nominally ordered U{sub 3}Ni{sub 3}Sn{sub 4} and CeCoIn{sub 5} systems, and the chemically disordered UCu{sub 4}Pd and CeRhRuSi{sub 2} systems.
Date: July 29, 2004
Creator: Booth, C.H.; Han, S.-W.; Skanthakumar, S. & Sarrao, J.L.
Partner: UNT Libraries Government Documents Department

Electronic and magnetic structure of GaxFe1-x thin films

Description: The electronic as well as magnetic properties of Ga{sub x}Fe{sub 1-x} films were studied by soft x-ray measurements. Using x-ray magnetic circular dichroism the Fe majority-spin band was found to be completely filled for x {approx} 0.3. With further enhanced Ga content, the Fe moment as well as the angular dependence of the x-ray magnetic linear dichroism decrease strongly, which we attribute to the formation of D0{sub 3} precipitates. Moreover, the magnetocrystalline anisotropy drops significantly.
Date: September 8, 2010
Creator: Arenholz, E.; van der Laan, G.; McClure, A. & Idzerda, Y.
Partner: UNT Libraries Government Documents Department

Crystal and magnetic structure of stoichiometric YFe{sub 2}O{sub 4}

Description: Crystal structure of stoichiometric YFe{sub 2}O{sub 4} powder was studied by high-resolution neutron diffraction at room temperature, 225 K and 80 K. Rietveld refinements of the diffraction patterns give reasonable fits with space group R{bar 3}m (hexagonal) for room temperature, and with P{bar 1} (triclinic) for 225 K. However, the 80 K pattern cannot be fitted at all with the same triclinic symmetry, indicating that the structure is much more complicated. The magnetic reflection has been separated from those complex nuclear peaks by the polarization analysis. The magnetic structure is also fairly complicated both at 225 K and at 80 K.
Date: August 1, 1994
Creator: Katano, S.; Funahashi, S.; Matsumoto, T.; Iida, J.; Tanaka, M. & Cable, J.W.
Partner: UNT Libraries Government Documents Department

Magnetic phase transitions in epitaxial Fe/Cr superlattices

Description: The surface spin-flop and Neel transitions are examined in Fe/Cr superlattices. The surface spin-flop, originally predicted by Mills [Phys. Rev. Lett. 20, 18 (1968)], is observed in Fe/Cr(211) superlattices with antiferromagnetic interlayer coupling and uniaxial in-plane-anisotropy. The Neel transition (T{sub N}) of Cr is observed in Fe/Cr(001) superlattices, for which the onset of antiferromagnetism is at a thickness t{sub Cr} of 42{angstrom}. The bulk value of T{sub N} is approached asymptotically as t{sub Cr} increases and is characterized by a three-dimensional shift exponent. These T{sub N} results are attributed to finite-size effects and spin-frustration near rough Fe-Cr interfaces.
Date: December 31, 1995
Creator: Fullerton, E.E.; Sowers, C.H.; Bader, S.D.; Riggs, K.T. & Berger, A.
Partner: UNT Libraries Government Documents Department

Raman and NMR Investigation of Molecular Reorientation and Internal Rotation in Liquids

Description: Molecular rotational motions are known to influence both Raman scattering of light and nuclear spin relaxation. Therefore, the application of Raman bandshape analysis and NMR relaxation time measurements to probe molecular dynamics in liquids will provide us with a deeper understanding of the dynamical behavior and structure of molecules in the liquid phase. Presented here are (i) studies of molecular reorientation of acetonitrile in the neat liquid phase and in solution by Raman bandshape analysis and NMR relaxation; (ii) studies of reorientational dynamics and internal rotation in transition metal clusters by NMR relaxation.
Date: December 1991
Creator: Yuan, Peng
Partner: UNT Libraries

Computer Programs Using Zonal Harmonics for Magnetic Properties of Current Systems with Special Reference to the IBM 7090

Description: Report that "discusses the magnetic vector and scalar potentials, magnetic field components and their derivatives, and flux linkage for single current systems, and the mutual inductance, forces and torques between two such systems, whose axes are coplanar but not necessarily coincident" (p. 1).
Date: December 4, 1962
Creator: Garrett, M. W.
Partner: UNT Libraries Government Documents Department

Hybrid magnetic tunnel junction/spin filter device

Description: Surfaces and interfaces of complex oxides materials provide a rich playground for the exploration of novel magnetic properties not found in the bulk but also the development of functional interfaces to be incorporated into applications. We have recently been able to demonstrate a new type of hybrid spin filter/ magnetic tunnel junction. Our hybrid spin-filter/magnetic-tunnel junction devices are epitaxial oxide junctions of La{sub 0.7}Sr{sub 0.3}MnO{sub 3} and Fe{sub 3}O{sub 4} electrodes with magnetic NiMn{sub 2}O{sub 4} barrier layers. Depending on whether the barrier is in a paramagnetic or ferromagnetic state, the junction exhibits magnetic tunnel junction behavior where the spin polarized conduction is dominated by the electrode-barrier interface or spin filter behavior where conduction is dominated by barrier layer magnetism.
Date: July 10, 2008
Creator: Suzuki, Y.; Nelson-Cheeseman, B.; Wong, F.; Chopdekar, R.; Arenholz, E.; Chi, Miaofang et al.
Partner: UNT Libraries Government Documents Department

Probing Compositional Variation within Hybrid Nanostructures

Description: We present a detailed analysis of the structural and magnetic properties of solution-grown PtCo-CdS hybrid structures in comparison to similar free-standing PtCo alloy nanoparticles. X-ray absorption spectroscopy is utilized as a sensitive probe for identifying subtle differences in the structure of the hybrid materials. We found that the growth of bimetallic tips on a CdS nanorod substrate leads to a more complex nanoparticle structure composed of a PtCo alloy core and thin CoO shell. The core-shell architecture is an unexpected consequence of the different nanoparticle growth mechanism on the nanorod tip, as compared to free growth in solution. Magnetic measurements indicate that the PtCo-CdS hybrid structures are superparamagnetic despite the presence of a CoO shell. The use of X-ray spectroscopic techniques to detect minute differences in atomic structure and bonding in complex nanosystems makes it possible to better understand and predict catalytic or magnetic properties for nanoscale bimetallic hybrid materials.
Date: June 22, 2010
Creator: Yuhas, Benjamin D.; Habas, Susan E.; Fakra, Sirine C. & Mokari, Taleb
Partner: UNT Libraries Government Documents Department

First-order transitions, symmetry, and the element of-expansion

Description: The group theoretical method of Landau and Lifshitz was used to derive effective Hamiltonians for certain paramagnetic to antiferromagnetic transitions having order-parameters with n greater than or equal to 4 components. A renormalization group analysis in 4-epsilon dimensions was performed. The first- order nature of the order-disorder transitions in Cr(n = 12), Eu(n = 12), UO$sub 2$(n = 6), and MnO(n = 8) can be explained by noting that the corresponding Hamiltonians possess no stable fixed points in 4-epsilon dimensions. It is predicted that all fcc type I(anti m perpendicular anti k), type II and type III(anti m perpendicular [100], anti k = [1/2 01]) antiferromagnetic transitions are first-order. The work is intended to serve as a guide in an experimental search for new examples of first-order transitions. A 2m-component Hamiltonian is also considered which possesses a unique, nonisotropic, stable fixed point for each value of 2m greater than or equal to 4. When 2m = 4, the Hamiltonian describes the paramagnetic to antiferromagnetic transitions in TbAu$sub 2$, DyC$sub 2$, Tb, Ho, Dy, and the structural transition in NbO$sub 2$. If these transitions are second-order, it is predicted they all belong to the same universality class. For 2m = 6, the Hamiltonian describes the antiferromagnetic transitions in TbD$sub 2$, Nd, K$sub 2$IrCl$sub 6$, and MnS$sub 2$. These transitions belong to a single universality class. (auth)
Date: January 1, 1975
Creator: Mukamel, D.; Krinsky, S. & Bak, P.
Partner: UNT Libraries Government Documents Department

Glass Forming Ability, Magnetic Properties, and Mechanical Behavior of Iron-Based and Cobalt-Based Metallic Glasses

Description: Lack of crystalline order and microstructural features such as grain/grain-boundary in metallic glasses results in a suite of remarkable attributes including very high strength, close to theoretical elasticity, high corrosion and wear resistance, and soft magnetic properties. In particular, low coercivity and high permeability of iron and cobalt based metallic glass compositions could potentially lead to extensive commercial use as magnetic heads, transformer cores, circuits and magnetic shields. In the current study, few metallic glass compositions were synthesized by systematically varying the iron and cobalt content. Thermal analysis was done and included the measurement of glass transition temperature, crystallization temperature, and the enthalpies of relaxation and crystallization. Magnetic properties of the alloys were determined including saturation magnetization, coercivity, and Curie temperature. The coercivity was found to decrease and the saturation magnetization was found to increase with the increase in iron content. The trend in thermal stability, thermodynamic properties, and magnetic properties was explained by atomic interactions between the ferromagnetic metals and the metalloids atoms in the amorphous alloys. Mechanical behavior of iron based metallic glasses was evaluated in bulk form as well as in the form of coatings. Iron based amorphous powder was subjected to high power mechanical milling and the structural changes were evaluated as a function of time. Using iron-based amorphous powder precursor, a uniform composite coating was achieved through microwave processing. The hardness, modulus, and wear behavior of the alloys were evaluated using nano-indentation.
Date: December 2014
Creator: Veligatla, Medha
Partner: UNT Libraries

Magneto-Optical and Chaotic Electrical Properties of n-InSb

Description: This thesis investigation concerns the optical and nonlinear electrical properties of n-InSb. Two specific areas have been studied. First is the magneto-optical study of magneto-donors, and second is the nonlinear dynamic study of nonlinear and chaotic oscillations in InSb. The magneto-optical study of InSb provides a physical picture of the magneto-donor levels, which has an important impact on the physical model of nonlinear and chaotic oscillations. Thus, the subjects discussed in this thesis connect the discipline of semiconductor physics with the field of nonlinear dynamics.
Date: December 1991
Creator: Song, Xiang-Ning
Partner: UNT Libraries

Magnetic x-ray circular dichroism in nickel-gold multilayers

Description: Magnetic circular dichroism in x-ray absorption is used to investigate the in-plane, remnant magnetization of well-characterized Ni{sub 0.48}/Au{sub 0.52} multilayers. Large superlattice strains are found in this multilayer system for samples with a 2nm layer pair spacing. A larger dichroism is found in the Ni 2p absorption edge for a 1.8 nm than for a 4.4 nm layer pair sample. The larger dichroism is consistent with a larger magnitude of in-plane strain for the Ni layers and a larger total magnetic anisotropy energy as previously shown from magnetization curves.
Date: November 11, 1994
Creator: Jankowski, A.F.; Tobin, J.G. & Waddill, G.D.
Partner: UNT Libraries Government Documents Department

Strongly correlated electronic materials

Description: This is the final report of a 3-year project. Novel electronic materials characterized by strong electronic correlations display a number of unexpected, often extraordinary, properties. These are likely to play a major role in purpose-specific high-technology electronic materials of the future developed for electronic, magnetic, and optical applications. This project sought to develop predictive control of the novel properties by formulating, solving and applying many-body models for the underlying microscopic physics. This predictive control required the development of new analytical and numerical many-body techniques and strategies for materials of varying strengths of interactions, dimensionality and geometry. Results are compared with experiment on classes of novel materials, and the robust techniques are used to predict additional properties and motivate key additional experiments.
Date: April 1, 1996
Creator: Bedell, K.; Albers, R.; Balatsky, A.; Bishop, A.; Bonca, J.; Gubernatis, J. et al.
Partner: UNT Libraries Government Documents Department