J. Schefer

A versatile double-axis multicounter neutron powder diffractometer

The double-axis multicounter diffractometer (DMC) installed at the 10-MW reactor SAPHIR (PSI) has been designed as a good-flux, good-resolution (presently Δd/d ⩾ 4×10−3) neutron powder diffractometer. The detector bank is based on a commercial position-sensitive linear BF3 detector which may be automatically and precisely positioned on air cushions (standard epoxy floor). Vertically variable focusing germanium or pyrolythic graphite monochromators are used. Special efforts were made to optimize the sample environment, e.g. by developing an oscillating radial collimator system. Although the monochromator shielding is not yet in a final state, the diffractometer is successfully operating since several years. Design properties and operational experience are discussed. Online data analysis based on LSI and VAX computers is facilitated by user-friendly software.

Giant lifetimes of optically excited states and the elusive structure of sodiumnitroprusside

The properties of sodiumnitroprusside (Na2[Fe(CN)5NO]*2H2O) are investigated by density functional theory. The calculated results both for the free anions as well as for the solid show that the ground-state Born–Oppenheimer surface has local minima for sidewards bonded and inverted NO. The calculated properties for the local minima: very long lifetime because of large barrier, diamagnetism, optical excitation energies, vibrational, and Mossbauer properties are in essential agreement with experiment. The present findings elucidate the possibility of population transfers by illumination with light of different wavelengths.

Simultaneous antiferromagnetic Fe3+ and Nd3+ ordering in NdFe3(11BO3)4

By means of magnetic susceptibility and specific heat measurements, x-ray and unpolarised neutron diffraction investigations on powder and single-crystal samples, simultaneous long-range antiferromagnetic Fe and Nd ordering in NdFe3(11BO3)4 with R 3 2 chemical structure has been found at temperatures below TN = 30.5(5) K down to 1.6 K. At temperatures down to 20 K to the propagation vector is khex = [0,0,3/2] and becomes slightly incommensurate at lower temperatures. Symmetry analysis yields magnetic spiral configurations with the magnetic moments oriented parallel to hexagonal basal plane according to the irreducible representations tau_3 in the commensurate case. This is in agreement with the easy directions of magnetisation perpendicular to the c-axis as determined by magnetic susceptibility measurements. At 1.6 K the magnetic Fe moment amounts to 4.9 muB close to the free ion moment of Fe3+. The magnetic Nd3+ moment saturates presumably due to crystal-field effects at 2.7 muB.

Single magnetic chirality in the magnetoelectric NdFe3(11BO3)4

We have performed an extensive study of single-crystals of the magneto-electric NdFe

The Swiss Spallation Neutron Source SINQ at Paul Scherrer Institut

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Spiral spin structures and origin of the magnetoelectric coupling in YMn2O5

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Single-crystal diffraction instrument TriCS at SINQ

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Reducing the positional modulation of NbO6-octahedra in SrxBa1–xNb2O6 by increasing the barium content: A single crystal neutron diffraction study at ambient temperature for x = 0.61 and x = 0.34

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Magnetoelastic coupling in the triangular lattice antiferromagnet CuCrS2

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Field-induced magnetic phases and electric polarization in LiNiPO4

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