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Scintillator‐based ZnS:Ag/6LiF neutron detectors have been under development at ISIS for more than three decades. Continuous research and development aim to improve detector capabilities, achieve better performance and meet the increasingly demanding requirements set by neutron instruments. As part of this program, a high‐efficiency 2D position‐sensitive scintillator detector with wavelength‐shifting fibres has been developed for neutron‐diffraction applications. The detector consists of a double scintillator‐fibre layer to improve detection efficiency. Each layer is made up of two orthogonal fibre planes placed between two ZnS:Ag/6LiF scintillator screens. Thin reflective foils are attached to the front and back scintillators of each layer to minimize light cross‐talk between layers. The detector has an active area of 192 × 192 mm with a square pixel size of 3 × 3 mm. As part of the development process of the double‐layer detector, a single‐layer detector was built, together with a prototype detector in which the two layers of the detector could be read out separately. Efficiency calculations and measurements of all three detectors are discussed. The novel double‐layer detector has been installed and tested on the SXD diffractometer at ISIS. The detector performance is compared with the current scintillator detectors employed on SXD by studying reference crystal samples. More than a factor of 3 improvement in efficiency is achieved with the double‐layer wavelength‐shifting‐fibre detector. Software routines for further optimizations in spatial resolution and uniformity of response have been implemented and tested for 2D detectors. The methods and results are discussed in this manuscript. [ABSTRACT FROM AUTHOR]

X-ray diffraction and infrared spectroscopy measurements are conducted in order to assess the crystallographic structure and chemical purity of lanthanum oxide (La2O3) films grown by atomic layer deposition (ALD) on Si substrates. In situ capping with thin aluminum oxide (Al2O3) layer is proved to be beneficial in preventing the formation of lanthanum hydroxide phases. The effect of two process parameters, namely, La2O3 film growth temperature (260–500 °C range) and postdeposition annealing temperature (600–1100 °C range), on the chemical and structural evolutions of Al2O3/La2O3/Si stacks is discussed. This study enables the identification of the optimum ALD growth recipe yielding the highest hexagonal La2O3 phase content, which might be suitable for integration into innovative metal oxide semiconductor devices. [ABSTRACT FROM AUTHOR]

La2O3 films are obtained by annealing in vacuum La(OH)3 layers produced upon air exposure of La2O3 layers grown using atomic layer deposition. Sample thickness determines whether hexagonal or cubic La2O3 form. The observed infrared active phonon mode with minimum frequency for hexagonal La2O3 films is located at 198 cm-1, in good agreement with the first principles calculations, and at a lower frequency than the corresponding mode for cubic La2O3 is at 235 cm-1. Accordingly, electrical measurements reveal a dielectric constant around 27 for hexagonal La2O3 films, significantly higher than the one around 17 derived for cubic La2O3 layers. [ABSTRACT FROM AUTHOR]

This article presents a correction of an earlier published article regarding the properties of lanthanum films.

Determining the fate of the Pauling entropy in the classical spin ice material Dy2Ti2O7 with respect to the third law of thermodynamics has become an important test case for understanding the existence and stability of ice-rule states in general. The standard model of spin ice--the dipolar spin ice model--predicts an ordering transition at T≈0.15 K, but recent experiments by Pomaranski et al. suggest an entropy recovery over long timescales at temperatures as high as 0.5 K, much too high to be compatible with the theory. Using neutron scattering and specific heat measurements at low temperatures and with long timescales (0.35 K/106 s and 0.5 K/105 s, respectively) on several isotopically enriched samples, we find no evidence of a reduction of ice-rule correlations or spin entropy. High-resolution simulations of the neutron structure factor show that the spin correlations remain well described by the dipolar spin ice model at all temperatures. Furthermore, by careful consideration of hyperfine contributions, we conclude that the original entropy measurements of Ramirez et al. are, after all, essentially correct: The short-time relaxation method used in that study gives a reasonably accurate estimate of the equilibrium spin ice entropy due to a cancellation of contributions. [ABSTRACT FROM AUTHOR]

Scintillator-based ZnS:Ag/ 6 LiF neutron detectors have been under development at ISIS for more than three decades. Continuous research and development aim to improve detector capabilities, achieve better performance and meet the increasingly demanding requirements set by neutron instruments. As part of this program, a high-efficiency 2D position-sensitive scintillator detector with wavelength-shifting fibres has been developed for neutron-diffraction applications. The detector consists of a double scintillator-fibre layer to improve detection efficiency. Each layer is made up of two orthogonal fibre planes placed between two ZnS:Ag/ 6 LiF scintillator screens. Thin reflective foils are attached to the front and back scintillators of each layer to minimize light cross-talk between layers. The detector has an active area of 192 × 192 mm with a square pixel size of 3 × 3 mm. As part of the development process of the double-layer detector, a single-layer detector was built, together with a prototype detector in which the two layers of the detector could be read out separately. Efficiency calculations and measurements of all three detectors are discussed. The novel double-layer detector has been installed and tested on the SXD diffractometer at ISIS. The detector performance is compared with the current scintillator detectors employed on SXD by studying reference crystal samples. More than a factor of 3 improvement in efficiency is achieved with the double-layer wavelength-shifting-fibre detector. Software routines for further optimizations in spatial resolution and uniformity of response have been implemented and tested for 2D detectors. The methods and results are discussed in this manuscript., (© Giacomo Mauri et al. 2024.)

In the three-dimensional oxalate network structures [M(II)(bpy)3][M(I)-M(III)(ox)3] (ox= C2O4(2-); bpy = 2,2'-bipyridine) the negatively charged oxalate backbone provides perfect cavities for tris-bipyridyl complex cations. The size of the cavity can be adjusted by variation of the metal ions of the oxalate backbone. In [Co(bpy)3][NaCr(ox)3], the [Co(bpy)3]2 + complex is in its usual 4T1(t2g5e(g)2) high-spin ground state. Substituting Na+ by Li+ reduces the size of the cavity. The resulting chemical pressure destabilises the high-spin state of [Co(bpy)3]2+ to such an extent that the 2E(t2g6e(g)1) low-spin state becomes the actual ground state. As a result. [Co(bpy)3][LiCr(ox)3] becomes a spin-crossover system, as shown by temperature-dependent magnetic susceptibility measurements and single-crystal optical spectroscopy, as well as by an X-ray structure determination at 290 and 10 K.