Magnetic Quantum Tunneling: Insights from Simple Molecule-Based Magnets

This article takes a broad view of the understanding of magnetic bistability and magnetic quantum tunneling in single-molecule magnets (SMMs), focusing on three families of relatively simple, low-nuclearity transition metal clusters: spin S = 4 Ni4, Mn(III)3 (S = 2 and 6) and Mn(III)6 (S = 4 and 12). The Mn(III) complexes are related by the fact that they contain triangular Mn3 units in which the exchange may be switched from antiferromagnetic to ferromagnetic without significantly altering the coordination around the Mn(III) centers, thereby leaving the single-ion physics more-or-less unaltered. This allows for a detailed and systematic study of the way in which the individual-ion anisotropies project onto the molecular spin ground state in otherwise identical low- and high-spin molecules, thus providing unique insights into the key factors that control the quantum dynamics of SMMs, namely: (i) the height of the kinetic barrier to magnetization relaxation; and (ii) the transverse interactions that cause tunneling through this barrier. Numerical calculations are supported by an unprecedented experimental data set (17 different compounds), including very detailed spectroscopic information obtained from high-frequency electron paramagnetic resonance and low-temperature hysteresis measurements. Diagonalization of the multi-spin Hamiltonian matrix is necessary in order to fully capture the interplay between exchange and local anisotropy, and the resultant spin-state mixing which ultimately gives rise to the tunneling matrix elements in the high symmetry SMMs (ferromagnetic Mn3 and Ni4). The simplicity (low-nuclearity, high-symmetry, weak disorder, etc..) of the molecules highlighted in this study proves to be of crucial importance.Comment: 32 pages, incl. 6 figure

Molecular and electronic structure of terminal and alkali metal-capped uranium(V) nitride complexes

Determining the electronic structure of actinide complexes is intrinsically challenging because inter-electronic repulsion, crystal field, and spin–orbit coupling effects can be of similar magnitude. Moreover, such efforts have been hampered by the lack of structurally analogous families of complexes to study. Here we report an improved method to U≡N triple bonds, and assemble a family of uranium(V) nitrides. Along with an isoelectronic oxo, we quantify the electronic structure of this 5f1 family by magnetometry, optical and electron paramagnetic resonance (EPR) spectroscopies and modelling. Thus, we define the relative importance of the spin–orbit and crystal field interactions, and explain the experimentally observed different ground states. We find optical absorption linewidths give a potential tool to identify spin–orbit coupled states, and show measurement of UV···UV super-exchange coupling in dimers by EPR. We show that observed slow magnetic relaxation occurs via two-phonon processes, with no obvious correlation to the crystal field

Этимологический анализ специальных единиц лексико-семантического поля "интеллектуальные энергетические системы" в системе современного английского языка

В данной статье описываются результаты этимологического анализа лексико-семантического поля "Интеллектуальные энергетические системы" современного английского языка. Этимологический анализ проводится в аспекте "семантической эволюции слова", а также принадлежности слова к собственному или заимствованному языковому материалу

EMR Data on Mn(III; S=2) Ions in MnTPPCl Complex Modelled by Microscopic Spin Hamiltonian Approach

The electron magnetic resonance data on high-spin (S =2) manganese(III) 3d⁴ ion in tetraphenylporphyrinato chloride complex (MnTPPCl) obtained by high-frequency techniques are reanalysed. Preliminary results of semiempirical modeling of the spin Hamiltonian parameters for Mn(III) in MnTPPCl are presented. The microscopic spin Hamiltonian approach is utilized to predict the zero-field splitting and the Zeeman electronic parameters. It is found that for Mn(III) ions in MnTPPCl matching the experimental spin Hamiltonian parameters and the theoretical ones based on the ligand-field energy levels (Δ_{i}) within the ⁵D multiplet only may not be suitable for this system. Contributions due to the levels arising from the higher-lying ³H multiplet need to be taken into account in order to determine the reasonable values of microscopic parameters describing Mn(III) ions in MnTPPCl

Solvent sublation of zinc(II) and manganese(II) from solution after acid leaching of chemical power sources

Produkty procesów kwaśnego ługowania odpadów chemicznych źródeł energii Zn-C i/lub Zn-Mn są potencjalnym źródłem cennych metali. Stosowane do tej pory rozwiązania pozwalają na stosunkowo łatwe przeprowadzenie wybranych pierwiastków do roztworów. Jednak w celu wytworzenia produktów, których postać byłaby korzystna zarówno z punktu widzenia technologicznego, jak i handlowego, konieczne jest opracowanie kolejnych jednostkowych procesów technologicznych. W prezentowanej pracy przedstawiono wyniki flotoekstrakcyjnego wydzielania jonów cynku(II) i manganu(II) za pomocą związków makrocyklicznych z rozcieńczonych roztworów po kwaśnym ługowaniu odpadów bateryjnych.Products of acid leaching of spent Zn-C and/or Zn-Mn batteries are possible source of valuable metals. Although there are some methods which are leading to successful transfer of chosen metals to a solution in these paper a novel approach to selective metal separation is presented. To achieve a product that will be both technically easy to achieve and commercially suitable solvent sublation process was used. Extraction ability of macrocyclic compounds in selective solvent sublation of zinc and manganese from diluted solutions was examined

Information technology oriented on spatial data in agriculture management support applications

Nowoczesne zarządzanie gospodarstwem rolniczym w głównej mierze bazuje lub będzie bazować na danych przestrzennych. Wykorzystanie do tego celu systemów GIS, które są między innym dostarczycielami tego typu danych, z perspektywy średnich i małych gospodarstw rolnych z uwagi na stopień trudności ich obsługi nie wydają się uzasadnionym rozwiązaniem. Alternatywę mogą stanowić prostsze aplikacje bazujące na technologiach informatycznych pozwalających na przetwarzanie danych przestrzennych. W niniejszym artykule, zaprezentowano oryginalny system informatyczny wspomagający zarządzanie danymi przestrzennymi na poziome realizacji usług rolniczych. Zbudowany on został na bazie technologii i narzędzi Microsoft. W publikacji zarysowano zarówno funkcjonalności powstałej aplikacji, jak i oceniono przydatność użytych technologii informatycznych.Modern management of agriculture is based chiefly, or it will be, on spatial data. Using GIS-systems for this purpose, which are, inter alia, providers of this kind of data, from medium and small agriculture farms' perspective are not a good solution since they are difficult to use. Simpler applications based on information technologies which can process spatial data may be an alternative. In this article, the authors present original IT system, which support management of spatial data at the level of agriculture services performance. The IT System was built at the base of technologies and tools provided by Microsoft. This publication outlines both functionality of the application and rates of the usefulness of the applied technologies