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The general performance of diffractometers at the first long pulse spallation source ESS, is compared with their counterparts at J-PARC, a short pulse spallation source. The difference in the inherent pulse structure of these neutron sources presents opportunities for new concepts for instrumentation, where performance does not scale simply with source power. The article describes advantages and disadvantages of those diffractometers, adapting to the very different source characteristics. We find that the two sources offer comparable performance in flux and resolution when operating in high-resolution mode. ESS offers significant advantages in tunability and flexibility, notably in the ability to relax resolution in order to increase flux for a given experiment. The slow repetition rate of ESS favors long instruments. On the other hand, J-PARC instruments perform very well in spite of the lower source power and allow better access to epithermal neutrons, of particular interest for PDF analysis of diffraction data.

The AMnO

Crystal structures of sodium cobalt oxide bilayer-hydrates were analyzed on the basis of superstructure models by assuming that the host and guest layers are commensurate. The superstructure model gave better fitting results compared to the incommensurate composite crystal model, suggesting that the host and guest layers are commensurate and have a 2 × 2 superstructure. Although the Co−O bonds in the superconductive CoO2 layers were reported to be shorter than that was expected from the Co oxidation states, the bond lengths refined in this study were consistent with the oxidation states.

Crystal structures of two kinds of cobalt oxide superconductors were investigated by neutron powder diffraction. Comparison between the structures of the two phases, one derived from γ-Na0.7CoO2 and the other from α-NaCoO2, indicated that the guest arrangement is common to the two phases in spite of the difference in stacking made of CoO2 host layers. Structure analysis on the basis of composite crystal models with stacking faults revealed that the hydrated sodium ions in the galleries are ordered to form a 2/ a × 2/ a trigonal lattice, where a is a lattice constant of the fundamental unit cell. The guest layers were found to be stacked along the c-direction with a short-range interlayer ordering: when a guest layer is stacked onto another over a CoO2 layer interposed between them, the stacking must be accompanied by a lateral shift with shift vectors, 1/2a2, 1/2b2, and 1/2a2 +1/2 b2, where a2 and b2 are lattice vectors of the 2/ a × 2/ a lattice with the same probability.

A first study of possible changes instigated by deuteration in amino acids was carried out using neutron diffraction, inelastic neutron scattering, and Raman scattering in l-alanine, C2H4(NH2)COOH. Careful analysis of the structural parameters shows that deuteration of l-alanine engenders significant geometric changes as a function of temperature, which can be directly related to the observation of new lattice vibration modes in the Raman spectra. The combination of the experimental data suggests that C2D4(ND2)COOD undergoes a structural phase transition (or a structural rearrangement) at about 170 K. Considering that this particular amino acid is a hydrogen-bonded system with short hydrogen bonds (O...H approximately 1.8 A), we evoke the Ubbelohde effect to conclude that substitution of hydrogen for deuterium gives rise to changes in the hydrogen-bonding interactions. The structural differences suggest distinct relative stabilities for the hydrogenous and deuterated l-alanine.

Time-resolved in situ neutron powder diffraction and Rietveld refinement have been used to study the synthesis of Bi-2212 from hydroxide precursors in a 2% O2 atmosphere. Bi-2212 was found to form within the temperature range 770–800 °C. Studies at 800 °C show that Bi-2212 grows rapidly at the expense of Bi-2201. Upon lowering the temperature to 500 °C and changing the atmosphere to Ar, a rapid increase in the lattice parameters was observed. We attribute this change to the loss of oxygen from the Bi-2212 lattice. The final material exhibited a Tc of 94 K.

A time-resolved neutron powder diffraction technique has been used to follow the changes occurring during the aging of magnesia-partially-stabilized zirconia at 1,100 C. Through quantitative phase analyses it has been possible to follow the development with aging time of tetragonal zirconia and of the [delta]-phase (Mg[sub 2]Zr[sub 5]O[sub 12], related to cubic, but with ordered anion vacancies), both at the expense of cubic zirconia. Changes in lattice parameters have been attributed to the expulsion of MgO stabilizer from the tetragonal zirconia precipitates as the aging proceeds. The broadening of peaks in the neutron diffraction pattern suggests there is considerable strain in the tetragonal precipitates in the c-direction, which is the short dimension in these lenticular precipitates. On cooling, there is some transformation of tetragonal zirconia to the monoclinic and orthorhombic phases.

Bilayer manganites La2-2xSr1+2xMn2O7 offer an exceptional opportunity to explore the connections among crystal structure, magnetic structure, and charge order. We have recently succeeded in synthesis of the phase diagram for x>0.5, and have used both neutron and X-ray diffraction to explore this highly Mn4+-rich system. In particular, we find a progression of magnetic structures from the type-A layered antiferromagnetic (AF), through the type-C AF rod structure, and finally to the type-G ‘rock salt’ AF structure. We also discover an unexpected region in which no long-range magnetic order is found and discuss a possible frustration scenario based on incompatible orbital ordering. We also address the evolution of charge order in these materials.

Neutron science has been a remarkable success story for European research. For this to continue, scientists need to be prepared to forge new networks and technologies.

The naturally layered colossal magnetoresistive manganites La2−2xSr1+2xMn2O7 exhibit an extremely varied range of magnetic and electronic behavior over a very narrow composition range between x=0.3 and x=0.5. The successful synthesis in our laboratories of compounds with nominally greater than 50%Mn4+ concentration has now allowed the study of this region of the phase diagram. Here we present detailed neutron diffraction measurements of these compounds with doping levels 0.5

We report powder neutron diffraction results on the crystal and magnetic structures of the bilayer Ruddlesden–Popper phase Sr3Mn2O7−δ (δ=0.0, 0.45) and correlate these structures with their magnetic and transport properties. The δ=0.45 compound contains a large number of oxygen vacancies that are disordered in the MnO2 planes. As a result of this disordered vacancy structure, Sr3Mn2O6.55 is a nonmagnetic insulator. Sr3Mn2O7.0 (δ=0) is an antiferromagnetic insulator whose magnetic structure is related to that of the SrMnO3 perovskite. Comparison of this end-member compound to its doped congeners in the La2−2xSr1+2xMn2O7 series highlights the extreme sensitivity of magnetic structure to dopant concentration in these layered materials.

Neutron scattering has been used to study the magnetic correlations in the double-layer manganite La1.2Sr1.8Mn2O7, which exhibits colossal magnetoresistance in the vicinity of the ferromagnetic transition at Tc=112 K. Over a large temperature range above Tc, there is evidence for two-dimensional magnetic correlations which peak in intensity at the transition. Although the in-plane correlations are predominantly ferromagnetic, a strong canting of spins in neighboring planes within the bilayers, at an angle that is dependent on both the temperature and magnetic field, is observed. There are indications of a crossover to three-dimensional critical scattering very close to Tc, but the nature of the phase transition has yet to be determined.

We report a switching of electronic, magnetic and lattice properties in honeycomb ruthenates by interlayer cation exchange. The new material Ag3LiRu2O6 was made by ion-exchange of the ordered Li/Ru honeycomb material Li2RuO3 in an AgNO3 melt at 200 °C. Neutron powder diffraction and electron microscopy show that the Li/Ru order is preserved in the honeycomb layers, however, significant stacking disorder is found between layers. In contrast to Li2RuO3, which is insulating, dimerised and diamagnetic, Ag3LiRu2O6 has low electrical resistivity (0.01 ohm cm−1) and a large magnetic susceptibility at room temperature. This is attributed to the electronic influence of the highly polarisable interlayer Ag+ cation. The combination of two dimensionality, good conductivity and stacking disorder means this family of materials have potential for thermoelectric applications.