Mixed anion systems, such as oxynitrides and oxyfluorides, are an emerging class of interesting materials. The lower stability of mixed anion systems in comparison to oxide materials has had the consequence that this area of materials research is relatively less well explored. However, the development of new synthesis techniques has resulted in the preparation of many new mixed anion systems and so a detailed understanding of their structure and how this relates to their electronic and magnetic properties is necessary. Within this Thesis, several oxide, oxynitride and oxyfluoride systems are investigated with a particular focus on the magnetic behaviour of materials based on geometrically frustrated pyrochlore and kagome lattices. The Lu2Mo2O7 pyrochlore contains a geometrically frustrated network of vertex sharing Mo4+ (d2 S = 1) tetrahedra. Here, the solid state synthesis of Lu2Mo2O7−x is reported along with a discussion of the coexistence of two cubic pyrochlore phases that has been discovered in samples synthesised at 1600 ◦C. Powder neutron diffraction and thermogravimetric analysis have revealed that this two-phase behaviour originates from a miscibility gap between stoichiometric Lu2Mo2O7 and oxygen deficient Lu2Mo2O6.6. Magnetic susceptibility and muon spin relaxation measurements support the formation of a geometrically frustrated spin glass ground state in Lu2Mo2O7 with a spin freezing temperature Tf ∼ 16 K. Low temperature neutron diffraction has confirmed the absence of long range magnetic order and magnetic diffuse neutron scattering data have indicated the presence of competing nearest and next nearest neighbour antiferromagnetic exchange interactions in the spin glass state. The magnetic heat capacity of Lu2Mo2O7 follows a T2-dependence at the low temperatures, indicating that Lu2Mo2O7 is another rare example of an unconventional, topological spin glass, which is stable in the absence of significant chemical disorder. The magnetic properties of the oxygen deficient pyrochlore phase Lu2Mo2O6.6 are qualitatively similar to those of Lu2Mo2O7, but an increase in the spin freezing temperature Tf ∼ 20 K suggests that oxygen-vacancy disorder in Lu2Mo2O6.6 favours the onset of a glassy state at higher temperatures and enhances the degree of frustration. Oxynitride pyrochlores with the ideal composition R2Mo2O5N2 (R = rare earth) contain Mo5+ d1 S = 1 2 cations on the frustrated pyrochlore lattice and are thus ideal candidates to support exotic magnetic ground states. Here, the synthesis of oxynitride pyrochlores of the Lu2Mo2O7 system by thermal ammonolysis is discussed alongside powder neutron diffraction and susceptibility data that show no evidence for long range magnetic order and an absence of spin freezing down to at least 2 K despite the persistence of strong antiferromagnetic exchange (θ = −120 K). A comparison of the magnetic diffuse neutron scattering between the spin glass state of Lu2Mo2O7 and the oxynitride is given, which suggests that the majority of the magnetic scattering in the oxynitride system is inelastic. In addition, low temperature magnetic heat capacity shows an absence of magnetic phase transitions and a continuous density of states through a T-linear dependence down to 500 mK. [NH4]2[C7H14N][V7O6F18], diammonium quinuclidinium vanadium(III,IV) oxyfluoride or DQVOF, is a kagome bilayer system with a geometrically frustrated two-dimensional kagome network of V4+ d1 S = 1 2 cations and V3+ d2 S = 1 cations between the kagome layers. Here, low temperature magnetisation and heat capacity data are presented, which demonstrate that the interplane V3+ d2 cations are well decoupled from the kagome layers at low temperatures such that DQVOF is a good experimental realisation of a S = 1 2 kagome antiferromagnet. Despite significant antiferromagnetic exchange (θ = −60 K) within the kagome planes, muon spin relaxation data have confirmed the absence of spin freezing and the persistence of internal field fluctuations that are intrinsic to the kagome layers down to temperatures of 40 mK. The low temperature heat capacity of the V4+ kagome network follows T-linear behaviour down to the 300 mK, highlighting the absence of a spin gap in the low energy excitation spectrum of DQVOF. The low temperature magnetic study of DQVOF presented here thus strongly supports the formation of a gapless quantum spin liquid phase. In the final results chapter, a discussion of the anion ordering principles in oxynitride systems is given. A high temperature, high resolution neutron diffraction study of the oxynitride perovskite SrTaO2N has revealed that the partial anion order that results in segregated Ta-N zig-zag chains is stable up to 1100 ◦C. Furthermore, these anion ordering principles are extended to the d1 perovskite oxynitrides RVO2−xN1+x (R = La, Nd, Pr) in a variable temperature neutron diffraction study, which confirms that the anion chain ordering discovered in d0 SrTaO2N is robust to electron doping. The R = La analogue also provides an interesting example of a rhombohedral oxynitride perovskite phase which coexists with an orthorhombic phase over the 4−300 K temperature range of the neutron diffraction study.

The langasites are a class of geometrically frustrated compounds with the formula A3XY3Z2O14 where A,X,Y,Z are cationic sites and site A is occupied by a magnetic ion. The interactions of the magnetic ions form a star shaped pattern called the Kagomé lattice. The langasites have been widely studied by the solid state community because of their functional properties such as piezoelectricity, multiferroicity, ferroelectricity, dielectricity and for use in the telecommunication industry. It was also realized that some langasite materials exhibit exotic magnetic ground states at low temperatures. A thorough understanding of their ground state is limited by the difficulty in synthesizing new members belonging to this series due to the formation of competing phases such as the garnets. In this study, four new magnetic langasites A3Ga3Ge2BeO14 (A= Pr, Nd, Sm and Eu) and a non-magnetic lattice standard La3Ga3Ge2BeO14 were synthesized. These were further structurally characterized by powder X-ray diffraction, Rietveld refinement and bond valence analysis. Further characterization of the low-temperature magnetism was done by performing magnetization, magnetic susceptibility (field cooled and zero field cooled) and heat capacity measurements. The low temperature spin dynamics were probed using muon spin resonance performed at TRIUMF (Vancouver) and elastic and inelastic neutron scattering measurements performed at the DCS (NIST) and D7 (ILL). From all the above measurements it can be concluded that the new Be langasites exhibit net antiferromagnetic interactions at low-temperatures with clear signs of diffuse scattering for Nd3Ga3Ge2BeO14 using inelastic neutron scattering measurements. There was no evidence of magnetic long-range ordering down to as low as 0.025 K. Based on the obtained measurements these new Be-langasite compounds can be classified as potential spin liquid candidates. / February 2017

In his seminal work, Out of the Crisis, W. Edwards Deming provided American corporations with a direction and method for improving both man and machine in an effort to transform the way in which these corporations performed and managed both service and industry functions. His ideas for statistical control have taken hold within the workplace and are becoming increasingly popular among managers and corporate executives who are intent on improving the bottom line. However, most companies have limited their incorporation of Deming's methods and failed to include Deming's approach to improved leadership and employee involvement. This study will review the human aspects of Deming's ideas and their convergence with an existing theory on employee engagement. Additionally, the impacts of employee engagement will be reviewed to better understand the potential gains that may be had by corporations when they implement Deming's Total Quality Management to the extent that he originally intended. / Contract number: N62271-97-G-0059

In this work we investigate themes related to many-body systems in which multiple ground states are accessible, a condition known as frustration. Frustration can arise in a number of contexts, and we consider the consequences of this situation with some examples from condensed-matter physics. In some magnetic materials interactions between spins are such that no single spin configuration provides a unique ground state. In the class of frustrated magnets where the number of ground states is extensive, thermal fluctuations are strong even at temperatures significantly below the interaction strength. At such temperatures spins are highly correlated, and small perturbations may have profound consequences. In this thesis we provide an example of this. By considering classical n-component spins with nearest-neigbour exchange on a frustrated octahedral lattice we show that – in the limit where exchange interactions are large – the system is in a disordered, correlated phase where correlations have the form of a dipole field. This is termed a Coulomb phase. From this phase we induce an ordering transition, lifting the degeneracy with weak, additional short-range interactions. By studying the transition in the solvable limit of n → ∞, we discover that the transition has identical thermodynamics to that of a magnetic system interacting through long-range, dipolar forces. Finally, we provide a more apposite characterisation of the transition, where the high-temperature side of the transition is described through the fluctuations of solenoidal fields, and the ordering corresponds to a condensation of these fields. In a separate part of the thesis, we investigate the influence of disorder on frustrated lattices. We study a two-dimensional tight-binding model with nearest-neighbour hopping and on-site disorder. Restricting the allowed states to being those from the low-lying manifold of ground states, the disorder feeds through to act as effective disorder in the hopping terms, which decay algebraically with distance. The quasi-long range nature of this effective hopping leads to a situation in which the resultant single-particle eigenstates are critical, and we probe their behaviour numerically with a transfer matrix calculation.

The extended kagome lattice, composed of alternating kagome and triangular layers, provides a novel geometry for frustrated magnetism. In this thesis, we study the properties of Heisenberg spins with nearest-neighbour antiferromagnetic interactions on this lattice. In common with many other models of frustrated magnets, this system has highly degenerate classical ground states. It is set apart from other examples, however, by the strong interlayer correlations between triangular layer spins. We study the implications of such correlations in both the statics and dynamics. We characterise classical ground states using a flux picture for a single layer of kagome spins, a theoretical description that sets geometrical bounds on correlations. We quantify the divergent but sub-extensive ground state degeneracy by a Maxwellian counting argument, and verify this calculation by analysing the energy eigenvalues of numerical ground states. We explore the ground state connectedness but do not reach firm conclusions on this issue. We use the self-consistent Gaussian approximation (SCGA) to calculate static spin correlations at finite temperature. The results of these calculations agree well with elastic neutron scattering experiments. We derive an expression for the effective interlayer interaction between kagome spins by integrating out the triangular lattice spins. We use linear spinwave theory to compute the spin excitation spectrum numerically. This shows encouraging similarity with inelastic neutron scattering data on a single-crystal YBaCo$_4$O$_7$ sample, for a wide range of wavevector and frequency. This agreement shows that our spin model is a reasonable description of the physics, and suggests that this numerical technique might be useful for other geometrically frustrated magnets. We study the dynamics analytically using the stochastic SCGA recently developed for the pyrochlore lattice. For technical reasons, we apply this technique on a related model, the stacked kagome lattice, rather than on the extended kagome lattice itself. From this we find slow relaxation at low temperature, with a rate ~ T² compared to the faster ~ T scaling for the pyrochlore. Strikingly, in simulations of the dynamics on the extended kagome lattice by numerical integration of the semiclassical equations of motion, we find two different relaxation rates. Kagome layer spins relax more quickly than the triangular layer spins, having ~ T.

The major problem investigated was to ascertain the extent to which a training program designed specifically to increase frustration tolerance would reduce selected behavioral problems in institutionalized mentally retarded children. Of lesser importance was the problem of examining the extent to which the prescribed training program had differential effects on brain-injured and non-brain-injured retarded children.

The investigation sought to examine resistance to extinction (Rn) as a function of previous experience with downward shifts in reward magnitude. It was suggested that previous research conducted within the framework of the Spence-Amsel frustration hypothesis and the sequential hypothesis failed to administer sufficient postshift trials to adequately establish the relationships that may exist. Under one condition, four groups of rats received twenty extinction trials following forty postshift trials. Under another condition, four groups were extinguished following eighty postshift trials. An inverse magnitude of reward effect occurred in the preshift phases, however, which prevented an adequate analysis of either the shift or the Rn data, This unexpected effect was discussed within the framework of Black's incentive-motivation interpretation of reinforcement.

The thesis is focused on issues of motivation for learning of pupils at the end of primary school. The first part of the thesis elaborates theoretical solutations to the process of the motivation for learning of pupils at school. It explains the definition of motivation in the pedagogical and psychological point of view. The thesis also introduces internal and external factors which are considered to create the motivation for learning. For the support of the motivation a teacher has to know the age specifics of the children, orientation of their personality and their learning style. The crucial sources of the motivation for learning are cognitive needs, social needs and achievement needs which participate in individual motivation orientation of children. In the case the needs are not developed or satisfied they may happen to be frustrated and manifested as boredom or fear. The action research in the second part ot the thesis watch which methods the class teacher uses to actualizate and develop the needs of her pupils. The complementary research is made with other teachers of the pupils at this age and investigates the competence to react to the motivation requirements of their pupils. This research also finds the subjective reactions of these pupils. The results of the research proved that pupils...

Computers have become an indispensable resource in assisting us in our daily life. While they do a good job most of the time, sometimes they can create a seemingly endless nightmare. Horrible user interfaces, bugs, errors, hardware issues and other factors are various causes of user frustration. The current approach is to either prevent it from happening or to fix the issue after it has appeared. In this study, an alternative approach is explored which makes use of distraction through mood induction. By using cute images of infantile animals it was argued that this could alleviate computer frustration. For this study, 60 participants were used to test this theory by first doing a frustrating task and a consequent treatment or control exposure. Mood and frustration levels were collected throughout the test and later analyzed. Additionally, opinions and reactions were collected using a follow-up interview and observations. Findings suggest that looking at cute images helps alleviate frustration caused by computers.

Cette thèse traite des propriétés des glaces de spins artificielles de type kagomé. Il s'agit de réseaux de nano-aimants magnétiques que nous avons fabriqués par dépôt d'un film mince, lithographie électronique et gravure ionique. Les éléments de la maille appelés brins possèdent des tailles typiques que 500 nm de long, 100 nm de large et 10nm d'épaisseur. L'intérêt de ces brins mésoscopiques repose sur la possibilité d'en déterminer la configuration magnétique par imagerie. Les caractérisations réalisées après désaimantation nous ont permis de mettre en évidence l'impact des différents types de désaimantation et de faire apparaître pour la première fois un polycristal de charges. Pour approfondir notre compréhension de ce système, nous avons aussi réalisé une étude numérique. Nous avons montré que les brins ne se comportent pas comme des spins d'Ising. En effet, la configuration d'aimantation d'un brin peut s'apparenter à une configuration homogène avec un domaine de fermeture aux deux extrémités. Nous avons étudié l'impact de ces configurations de bout de brins dans le renversement de l'aimantation des réseaux. Nous montrons également expérimentalement que le renversement peut être très anisotrope. L'origine de cette anisotropie a été étudiée. Enfin, nous montrons numériquement que lorsqu'une configuration interdite est stabilisée, les domaines de fermeture ferment le flux laissant apparaître deux chiralités qui possèdent des champs de disparition différents lorsque le champ est appliqué hors axe de la nanostructure. D'un point de vue expérimental, nous avons tenté de mettre en évidence l'existence de cette chiralité des monopoles / The subject of this thesis is the study of artificial kagome spin ices which are frustrated networks of nanomagnets. These arrays are made using thin film deposition, electron beam lithography and ion beam etching. The typical sizes of each nanomagnet are a length of 500nm, a width of 100nm and a thickness of 10nm with a separation between nanomagnets of 50nm. The interest of these frustrated networks relies on the possibility to measure the magnetic configurations by imagery and extract the macrospin configurations. In this work we have especially compared different demagnetization procedures (field and thermal) that allowed us to highlight their impact on the configurations and we have shown for the first time an emergent polycristal of charges. To have a better understanding of our system, we have also conducted a numerical study using finite difference methods. We have shown that nanomagnets do not behave like Ising spin. Indeed, the magnetic configuration is shown to be homogeneous with domains at extremities. In the array, the domains close the flux at a vertex and the effects of those domains on the magnetization reversal of our networks have been studied. We have also shown experimentally that the reversal can be anisotropic. The origin of this anisotropy has been studied. Finally, we have numerically shown that, when a forbidden configuration is stabilized, the closure of the flux at the vertex leads to chiralities of the forbidden state. These chiralities possess different annihilation fields when the fields are applied out of the nanostructure axis. From an experimental point of view, we tried to show the existence of this monopole chirality using adapted field histories