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Single crystals of LnMg 2 Bi 2 (Ln=Yb, Eu, Sm) and SmMg 2 Sb 2 were synthesized using Mg–Bi metal and Mg–Sb metal fluxes, respectively. The crystal structures are of the CaAl 2 Si 2 type with space group P 3 ̅ m1 (#164, Z =1): SmMg 2 Bi 2 ( a =4.7745(1) Å, c =7.8490(2) Å), EuMg 2 Bi 2 ( a =4.7702(1) Å, c =7.8457(2) Å), YbMg 2 Bi 2 ( a =4.7317(2) Å, c =7.6524(3) Å), and SmMg 2 Sb 2 ( a =4.6861(1) Å, c =7.7192(2) Å). Heat capacity, electrical transport, and magnetization of all bismuth containing phases were measured. The materials behave as “poor metals” with resistivity between 2 and 10 mΩ cm. Temperature independent Van Vleck paramagnetism is observed in SmMg 2 Bi 2 indicative of divalent samarium (Sm 2+ ) ions. [ABSTRACT FROM AUTHOR]

Abstract: Powder samples and single crystals of the new complex boride series Cr x (Rh1−y Ru y )7−x B3 (x=0.88–1; y=0–1) have been synthesized by arc-melting the elements under purified argon atmosphere on a water-cooled copper crucible. The products, which have metallic luster, were structurally characterized by single-crystal and powder X-ray diffraction as well as EDX measurements. Within the whole solid solution range the hexagonal Th7Fe3 structure type (space group P63 mc, no. 186, Z=2) was identified. Single-crystal structure refinement results indicate the presence of chromium at two sites (6c and 2b) of the available three metal Wyckoff sites, with a pronounced preference for the 6c site. An unexpected Rh/Ru site preference was found in the Ru-rich region only, leading to two different magnetic behaviors in the solid solution: The Rh-rich region shows a temperature-independent (Pauli) paramagnetism whereas an additional temperature-dependent paramagnetic component is found in the Ru-rich region. [Copyright &y& Elsevier]

Abstract: The heat capacity of a 13nm hematite (α-Fe2O3) sample was measured from T =(1.5 to 350)K using a combination of semi-adiabatic and adiabatic calorimetry. The heat capacity was higher than that of the bulk which can be attributed to the presence of water on the surface of the nanoparticles. No anomaly was observed in the heat capacity due to the Morin transition and theoretical fits of the heat capacity below T =15K show a small T 3 dependence (due to lattice contributions) with no T 3/2 dependence. This suggests that there are no magnetic spin-wave contributions to the heat capacity of 13nm hematite. The use of a large linear term to fit the heat capacity below T =15K is most likely due to superparamagnetic contributions. A small anomaly within the temperature range (4 to 8)K was attributed to the presence of uncompensated surface spins. [Copyright &y& Elsevier]

Abstract: Hyperpolarized xenon associated with ligand derivatized cryptophane-A cages has been developed as a NMR based biosensor. To optimize the detection sensitivity we describe use of xenon exchange between the caged and bulk dissolved xenon as an effective signal amplifier. This approach, somewhat analogous to ‘remote detection’ described recently, uses the chemical exchange to repeatedly transfer spectroscopic information from caged to bulk xenon, effectively integrating the caged signal. After an optimized integration period, the signal is read out by observation of the bulk magnetization. The spectrum of the caged xenon is reconstructed through use of a variable evolution period before transfer and Fourier analysis of the bulk signal as a function of the evolution time. [Copyright &y& Elsevier]

It is well known that in multi-pulse applications in high-resolution NMR and MRI a steady state is reached for the magnetisation vector by the effect of relaxation in combination with the pulse repetition time. In this paper, a mathematical model is developed to understand how the parameters of the pulse sequence and relaxation times T1 and T2 affect the behaviour of the magnetisation vector. It will be shown that even under strong simplifying conditions an analytical analysis becomes very complex and only an analytical solution can be found for 90° pulses and T1=T2. For other cases a numerical approach is needed. Nevertheless, the basic approach of the mathematical analysis provides a general tool for analytical multi-operator applications. Our results provide a quantitative insight in the process by which the magnetisation relaxes towards the steady-state situation in a multi-pulse sequence. [Copyright &y& Elsevier]