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3d -electron Heisenberg pyrochlore Mn2Sb2O7
Peets, Darren C.,Sim, Hasung,Avdeev, Maxim,Park, Je-Geun American Physical Society 2016 Physical Review B Vol.94 No.17
<P>In frustrated magnetic systems, geometric constraints or the competition among interactions introduce extremely high degeneracy and prevent the system from readily selecting a low-temperature ground state. The most frustrated known spin arrangement is on the pyrochlore lattice, but nearly all magnetic pyrochlores have unquenched orbital angular momenta, constraining the spin directions through spin-orbit coupling. Pyrochlore Mn2Sb2O7 is an extremely rare Heisenberg pyrochlore system with directionally unconstrained spins and low chemical disorder. We show that it undergoes a spin-glass transition at 5.5 K, which is suppressed by disorder arising from Mn vacancies, indicating this ground state to be a direct consequence of the spins' interactions. The striking similarities to 3d transition-metal pyrochlores with unquenched angular momenta suggests that the low spin-orbit coupling in the 3d block makes Heisenberg pyrochlores far more accessible than previously imagined.</P>
Efficiency enhancement in low-bandgap polymer solar cells by processing with alkane dithiols
Peet, J.,Kim, J. Y.,Coates, N. E.,Ma, W. L.,Moses, D.,Heeger, A. J.,Bazan, G. C. Nature Publishing Group 2007 NATURE MATERIALS Vol.6 No.7
High charge-separation efficiency combined with the reduced fabrication costs associated with solution processing and the potential for implementation on flexible substrates make ‘plastic’ solar cells a compelling option for tomorrow’s photovoltaics. Attempts to control the donor/acceptor morphology in bulk heterojunction materials as required for achieving high power-conversion efficiency have, however, met with limited success. By incorporating a few volume per cent of alkanedithiols in the solution used to spin-cast films comprising a low-bandgap polymer and a fullerene derivative, the power-conversion efficiency of photovoltaic cells (air-mass 1.5 global conditions) is increased from 2.8% to 5.5% through altering the bulk heterojunction morphology. This discovery can potentially enable morphological control in bulk heterojunction materials where thermal annealing is either undesirable or ineffective.
Modern Skyscrapers in the Late 19th Century
Peet, Gerard Council on Tall Building and Urban Habitat Korea 2020 International journal of high-rise buildings Vol.9 No.1
Skyscrapers are often seen as a typically American phenomenon. This paper aims at demonstrating that in terms oif technology major developments are European and that, albeit in lesser number and not as high as in the USA, skyscrapers were also built in the late 19th century in countrries other than the USA. The paper concludes with an overview of late 19th century non-US skyscrapers.
Magnetic transitions in the chiral armchair-kagome system Mn2Sb2O7
Peets, Darren C.,Sim, Hasung,Choi, Seongil,Avdeev, Maxim,Lee, Seongsu,Kim, Su Jae,Kang, Hoju,Ahn, Docheon,Park, Je-Geun American Physical Society 2017 Physical Review B Vol.95 No.1
<P>The competition between interactions in frustrated magnets allows a wide variety of new ground states, often exhibiting emergent physics and unique excitations. Expanding the suite of lattices available for study enhances our chances of finding exotic physics. Mn2Sb2O7 forms in a chiral, kagome-based structure in which a fourth member is added to the kagome-plane triangles to form an armchair unit and link adjacent kagome planes. This structural motif may be viewed as intermediate between the triangles of the kagome network and the tetrahedra in the pyrochlore lattice. Mn2Sb2O7 exhibits two distinct magnetic phase transitions, at 11.1 and 14.2 K, at least one of which has a weak ferromagnetic component. The magnetic propagation vector does not change through the lower transition, suggesting a metamagnetic transition or a transition involving a multicomponent order parameter. Although previously reported in the P3(1)21 space group, Mn2Sb2O7 actually crystallizes in P2, which allows ferroelectricity, and we show clear evidence of magnetoelectric coupling indicative of multiferroic order. The quasi-two-dimensional 'armchair-kagome' lattice presents a promising platform for probing chiral magnetism and the effect of dimensionality in highly frustrated systems.</P>
Upper critical field of the noncentrosymmetric superconductor BiPd
Peets, Darren C.,Maldonado, Ana,Enayat, Mostafa,Sun, Zhixiang,Wahl, Peter,Schnyder, Andreas P. American Physical Society 2016 Physical Review B Vol.93 No.17
<P>The superconducting parameters and upper critical field of the noncentrosymmetric superconductor BiPd have proven contentious. This material is of particular interest because it is a rare example of a 4f -electron-free noncentrosymmetric superconductor of which crystals may be grown and cleaved, enabling surface-sensitive spectroscopies. Here, using bulk probes augmented by tunneling data on defects, we establish that the lower of the previously reported upper critical fields corresponds to the bulk transition. The material behaves as a nearly weak-coupled BCS s-wave superconductor, and we report its superconducting parameters as drawn from the bulk upper critical field. Possible reasons behind the order-of-magnitude discrepancy in the reported upper critical fields are discussed.</P>
Finite, Fiber-preserving Group Actions on Elliptic 3-manifolds
Benjamin Peet 경북대학교 자연과학대학 수학과 2022 Kyungpook mathematical journal Vol.62 No.2
In two previous papers the author presented a general construction of finite, fiber- and orientation-preserving group actions on orientable Seifert manifolds. In this paper we restrict our attention to elliptic 3-manifolds. For illustration of our methods a constructive proof is given that orientation-reversing and fiber-preserving diffeomorphisms of Seifert manifolds do not exist for nonzero Euler class, in particular elliptic 3-manifolds. Each type of elliptic 3-manifold is then considered and the possible group actions that fit the given construction. This is shown to be all but a few cases that have been con sidered elsewhere. Finally, a presentation for the quotient space under such an action is constructed and a specific example is generated.
Application of Growth Models for Pigs in Practice -Review-
van der Peet-Schwering, C.M.C.,den Hartog, L.A.,Vos, H.J.P.M. Asian Australasian Association of Animal Productio 1999 Animal Bioscience Vol.12 No.2
Growth of pigs is influenced by many factors. To assist pig producers in the evaluation of alternative feeding and management strategies growth models have been developed. In the Netherlands the Technical Model Pigfeeding (TMV) is developed. This model predicts the influence of feed intake, feed composition, genotype, sex and climate on growth, body composition, gross margin and mineral excretion of healthy growing/finishing pigs. The purpose of TMV is to support information services, feed companies, researchers and students. In addition to providing accurate predictions, a model should also be user-friendly and wishes of the user should be taken into account to stimulate application of the model in practice. In this paper, the theoretical background of TMV and a methodology to stimulate application of models in practice will be described.