Throughout much of condensed matter science, correlated disorder is a key to material function. While structural and compositional defects are known to exist within a variety of metal–organic frameworks (MOFs), the prevailing understanding is that these defects are only ever included in a random manner. Here we show—using a combination of diffuse scattering, electron microscopy, anomalous X-ray scattering and pair distribution function measurements—that correlations between defects can in fact be introduced and controlled within a hafnium terephthalate MOF. The nanoscale defect structures that emerge are an analogue of correlated Schottky vacancies in rocksalt-structured transition metal monoxides and have implications for storage, transport, optical and mechanical responses. Our results suggest how the diffraction behaviour of some MOFs might be reinterpreted, and establish a strategy of exploiting correlated nanoscale disorder as a targetable and desirable motif in MOF design.

A software package for the calibration and processing of powder X-ray diffraction and small-angle X-ray scattering data is presented. It provides a multitude of data processing and visualization tools as well as a command-line scripting interface for on-the-fly processing and the incorporation of complex data treatment tasks. Customizable processing chains permit the execution of many data processing steps to convert a single image or a batch of raw two-dimensional data into meaningful data and one-dimensional diffractograms. The processed data files contain the full data provenance of each process applied to the data. The calibration routines can run automatically even for high energies and also for large detector tilt angles. Some of the functionalities are highlighted by specific use cases.

We report on detailed magnetic measurements on the cubic helimagnet FeGe in external magnetic fields and temperatures near the onset of long-range magnetic order at $T_C=278.2(3)\mathrm{K}$. Precursor phenomena display a complex succession of temperature-driven crossovers and phase transitions in the vicinity of $T_C$. The $A$-phase region, present below $T_C$ and fields $H<0.5\mathrm{kOe}$, is split in several pockets. The complexity of the magnetic phase diagram is theoretically explained by the confinement of solitonic kinklike or Skyrmionic units that develop an attractive and oscillatory intersoliton coupling owing to the longitudinal inhomogeneity of the magnetization.

We report on results of specific heat measurements on single crystals of the frustrated quasi-2D spin-$1/2$ antiferromagnet ${\mathrm{Cs}}_2{\mathrm{CuCl}}_4$ ($T_N=0.595\mathrm{K}$) in external magnetic fields $B<12\mathrm{T}$ and for temperatures $T>30\mathrm{mK}$. Decreasing $B$ from high fields leads to the closure of the field-induced gap in the magnon spectrum at a critical field $B_c\simeq 8.51\mathrm{T}$ and a magnetic phase transition is clearly seen below $B_c$. In the vicinity of $B_c$, the phase transition boundary is well described by the power law $T_c(B)\propto (B_c-B{)}^{1/\varphi }$, with the measured critical exponent $\varphi \simeq 1.5$. These findings are interpreted as a Bose-Einstein condensation of magnons.