This thesis describes the synthesis and magnetic characterisation of a series of polynuclear 3d and 3d/4f complexes built using phenolic oxime type ligands. Chapter two describes the reaction of salicylaldoxime and its derivatised analogues (R-saoH2) with the alkoxide containing co-ligands triethanolamine (TeaH3) and 2-(hydroxymethyl)pyridine (Hhmp), in the presence of Mn(II)/Ln(III) salts. This results in the formation of a family of sixteen [MnIII4LnIII2] clusters, which are structurally related to a previously studied [MnIII6] family of Single-Molecule Magnets (SMMs). The magnetic properties of the Ln = Y, Gd and Lu analogues can be qualitatively rationalised on the basis of a magneto-structural correlation (MSC), previously developed for MnIII alkoxide/oxime bridged dimers. Chapter three describes how the combination of two complimentary ligands, the phenolic oximes (R-SaoH2) and the diethanolamines (DeaH3), into one organic framework, creates new ligand types (H3L1 and H4L2) which can be used to construct a hexametallic MnIII wheel; [MnIII6Na(L1)6]Cl, the first example of a ferromagnetically coupled dodecametallic MnIII wheel;[MnIII 12(OMe)16(L2)4(O2CCMe3)4(MeOH)4], and the first example of a dodecametallic MnIII truncated tetrahedron; [MnIII12O4(H3L2)8(H2L2)4(TMA)4 (TMA = trianion of trimesic acid). Single crystal hysteresis measurements reveal both 3.2 and 3.3 to be SMMs at low temperature. Chapter four deals with the use of H4L2 in Cu coordination chemistry. Phenolic oximes are known to form monometallic complexes with CuII ions, as are the diethanolamines. However, the deliberate incorporation of one ligand onto the organic framework of the other permits the preparation of a family of [CuIIn] wheels (n = 4, 6, 8). In each case nearest neighbour interactions between CuII ions are shown to be strongly antiferromagnetic. DFT calculations suggest the origin of this interaction is related to the Cu-O-N-Cu dihedral angle, an observation which allows for the development of a theoretical MSC, that suggests a switch from antiferro- to ferro-magnetic exchange is possible at Cu-O-N-Cu angles > 60o.

Source: Dissertation Abstracts International, Volume: 24-01, page: 0337. / Thesis (Ph.D.)--The Florida State University, 1963.

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Measurements were made of the rate of magnetization, and the magnetization of the series of Dy (Co, Ni)2 compounds to investigate the intrinsic magnetic after effect. This effect is demonstrated by the existence of an intrinsic coercivity such that a critical value of applied field, Hc, must be reached before the domain walls can move freely through the material. However there is some movement of domain walls of fields below Hc, and this gives rise to time dependent magnetization. The mechanisms by which the domain walls overcome the energy barrier to their motion at fields below Hc was investigated in pulsed field, and in steady fields. After measuring the critical field and magnetic moments of each sample, the pulsed field magnetometer results were analysed to show that there is a certain temperature above which the mechanism for domain wall motion appears to be that described by Taylor???s thermal activation model. Below that particular temperature, the magnetization rate depends on the reciprocal of the applied field, and an empirical model is suggested. Estimates are made of the number of spines contained in the average wall kink; the wall jump frequency and the energy barrier. A vibrating sample magnetometer was used to study the magnetization of the specimens in steady fields. The results indicate that both the mechanisms described above are in operation, with thermal activation being a possibility at temperatures as low as 4.2K.

Photothermal energy conversion is important when designing optically active devices based on plasmonic nanoparticles. Many early applications of these nanoparticles, like photothermal tumor ablation, drug delivery, and microfluidic devices, depend on the conversion of light to heat. In this dissertation, we compare three nanoparticle species' theoretical absorption efficiency from electromagnetic calculations with their photothermal transduction efficiency from measurements of temperature in an illuminated system. Several mechanisms that may account for differences between the two efficiencies are suggested. With a view specifically toward clinical applications, our analysis assumes a random orientation of nanorods, as would occur naturally in the tumor vasculature. For the samples studied here, photothermal transduction efficiencies differed only by a factor of two or three, regardless of particle type and concentration. Both experiment and theory show that particle size plays a dominant role in determining transduction efficiency, with smaller particles more efficient for heating and larger particles for combined heating and imaging. Additionally, we evaluate the potential of mixtures of plasmonic nanoparticles for CO 2 scrubbing substrates that could be used in space applications. These measurements indicate possible dynamic nanoscale effects that need to be accounted for when modeling photothermal transduction.

This dissertation focuses on the exploratory synthesis of compounds that contain R6ZI12 (R= Ce, Gd, Er; Z=Mn, Fe, Co, C2) clusters with the goal of finding magnetically interesting compounds. Several new compounds were made via high temperature, solid state methods and structurally characterized using x-ray diffraction. Compounds that contain isolated clusters were studied in order to understand the magnetic coupling between lanthanide atoms. The exploration of transition metal centered clusters resulted in the discovery of two new structure types, CsR(R6CoI12)2 (R=Gd and Er) and (CeI)0.26(Ce6MnI9)2. The xray crystal structure of CsEr(Er6CoI12)2 was solved in the Pa3 – space group with the cell length 18.063(2) Å at 250K (Z = 4, R1 [I>2σ(I)] = 0.0459). (CeI)0.26(Ce6MnI9)2 was made by combining KI, CeI3, MnI2 and Ce metal and heating to 850°C for 500 hrs. The single crystal x-ray structure for (CeI)0.26(Ce6MnI9)2 was solved in the trigonal, P3 – space group with lattice parameters of a = 11.695(1) Å c = 10.8591(2) Å (Z = 2, R1 [I>2σ(I)] = 0.0895). The magnetic susceptibilities of hexanuclear gadolinium clusters in the compounds Gd(Gd6ZI12) (Z = Co, Fe or Mn), CaxGd1-x(Gd6MnI12) and CsGd(Gd6CoI12)2 are reported. The single-crystal structure of Gd(Gd6CoI12) and CaxGd1-x(Gd6MnI12) are reported here as well. The compound with a closed shell of cluster bonding electrons, Gd(Gd6CoI12), exhibits the effects of antiferromagnetic coupling over the entire range of temperatures measured (4 - 300 K). Clusters with unpaired, delocalized cluster bonding electrons (CBEs) exhibit enhanced susceptibilities consistent with strong ferromagnetic coupling, except at lower temperatures (less than 30 K) where intercluster antiferromagnetic coupling suppresses the susceptibilities. Four new compounds containing Gd6C2 clusters have been found: Gd6C2I11, Gd(Gd6C2I12), CsGd(Gd6C2I12)2 and Cs(Gd6C2I12). Gd6C2I11 and Cs(Gd6C2I12) crystallized in the P1 space group while Gd(Gd6C2I12) and CsGd(Gd6C2I12)2 crystallized in the R3 and Pa3 space groups respectively. The magnetic susceptibility data for Cs(Gd6C2I12) indicate strong intracluster ferromagnetic coupling, but antiferromagnetic coupling suppresses the susceptibility below 150 K. DFT calculations on CsGd6C2I12 and molecular models indicate that the magnetic coupling between the basal Gd atoms is stronger than the magnetic coupling involving the axial Gd atoms in the distorted clusters.

Al-rich Fe-Al systems (FeAl2, Fe2 Al5 and Fe4Al13) and Al20V2Eu have complicated structures with quasicrystal-like features making these materials potentially of interest for magnetic behavior. However, there is not much work on these materials. To study the variety of magnetic properties, we use NMR, magnetic susceptibility, specific heat and other methods in this work. The microscopic electronic and magnetic properties of the Al-rich Fe-Al system and Al20V2Eu have been studied via 27Al NMR at temperatures between 4 and 500 K. The results of spin lattice relaxation rates reveal a pseudogap in Fe4Al13 and Fe2Al5 around the Fermi-level in the density of states. Besides, a square well gap with a width of 2 meV and center at Fermi energy was detected by specific heat measurements in Fe2Al5. Both Fe4 Al13 and Fe2Al5 are non-magnetic systems with dilute magnetic defects, while FeAl2 is a concentrated local magnetic moment system. In Al20V2Eu, a crossover was observed in NMR, magnetization and transport measurements. Above 40 K, Eu(2+) local magnetic moments dominate; below 40 K, a transition to a Kondo regime is observed, where the Kondo effect leads to the reduction of localized moments due to the formation of a spin-compensated Kondo cloud. With increasing magnetic field, f electrons participate more and more in excitations near the Fermi level and a heavy-Fermion state was observed through specific heat measurements at high magnetic field.

<p>This doctoral thesis presents density functionalcalculations applied in several domains of interest in solidstate physics and materials science. Non-collinear magnetismhas been studied both in an artificial multi-layer structure,which could have technological relevance as a magnetic sensordevice, and as excitations in 3d ferromagnets. The intricatebulk crystal structure of γ-alumina has been investigated.An improved embedded cluster method is developed and applied tostudy the geometric and electronic structures and opticalabsorption energies of neutral and positively charged oxygenvacancies in α-quartz. Ab initio total energycalculations, based on the EMTO theory, have been used todetermine the elastic properties of Al_1-xLi_xrandom alloys in the face-centered cubiccrystallographic phase. The obtained overall good agreementwith experiment demonstrates the applicability of the quantummechanics formulated within the framework of the DensityFunctional Theory for mapping the structural and mechanicalproperties of random alloys against chemical composition.</p>

Thesis (doctoral)--Friedrich-Wilhelms-Universität Berlin, 1853. / Vita.

Thesis (Ph. D.)--Ohio State University, 2003. / Title from first page of PDF file. Document formatted into pages; contains xiii, 303 p.; also includes graphics (some col.). Includes abstract and vita. Advisor: Lei Bao, Dept. of Physics. Includes bibliographical references (p. 299-303).