High-energy photoemission on Fe3O4: Small polaron physics and the Verwey transition

We have studied the electronic structure and charge ordering (Verwey) transition of magnetite (Fe3O4) by soft x-ray photoemission. Due to the enhanced probing depth and the use of different surface preparations we are able to distinguish surface and volume effects in the spectra. The pseudogap behavior of the intrinsic spectra and its temperature dependence give evidence for the existence of strongly bound small polarons consistent with both dc and optical conductivity. Together with other recent structural and theoretical results our findings support a picture in which the Verwey transition contains elements of a cooperative Jahn-Teller effect, stabilized by local Coulomb interaction

Short-Range B-site Ordering in Inverse Spinel Ferrite NiFe2O4

The Raman spectra of single crystals of NiFe2O4 were studied in various scattering configurations in close comparison with the corresponding spectra of Ni0.7Zn0.3Fe2O4 and Fe3O4. The number of experimentally observed Raman modes exceeds significantly that expected for a normal spinel structure and the polarization properties of most of the Raman lines provide evidence for a microscopic symmetry lower than that given by the Fd-3m space group. We argue that the experimental results can be explained by considering the short range 1:1 ordering of Ni2+ and Fe3+ at the B-sites of inverse spinel structure, most probably of tetragonal P4_122/P4_322 symmetry.Comment: 10 pages, 5 figures, 6 table

Thermomagnetic history effects in SmMn2_2Ge2_2

The intermetallic compound SmMn$_2$Ge$_2$, displaying multiple magnetic phase transitions, is being investigated in detail for its magnetization behavior near the 145 K first order ferromagnetic to antiferromagnetic transition occuring on cooling, in particular for thermomagnetic history effects in the magnetization data. The most unusual finding is that the thermomagnetic irreversibility, [= M$^{FCW}$(T)-M$^{ZFC}$(T)] at 135 K is higher in intermediate magnetic field strengths. By studying the response of the sample (i.e., thermomagnetic irreversibility and thermal hysteresis) to different histories of application of magnetic field and temperature, we demonstrate how the supercooling and superheating of the metastable magnetic phases across the first order transition at 145 K contribute to overall thermomagnetic irreversibility.Comment: 15 pages, 5 figures, to appear in Physical Review

The Dutch Citizen's Understanding and Perception of the Actors Involved in the Netherlands' COVID-19 Pandemic Response:A Focus Group Study During the First Pandemic Wave

Introduction: The COVID-19 pandemic was a public health emergency (PHE) of unprecedented magnitude and impact. It provided the possibility to investigate the Dutch citizens' understanding and perception of the actors involved in the Dutch pandemic response as a PHE unfolded. Methods: Three focus groups (FGs) were held with 16 Dutch citizens in June 2020. Citizens were recruited using the Dutch Health Care Consumer Panel. During the FGs, participants were asked to fill in a table with actors they thought were involved in the management of the COVID-19 pandemic. They also received information on actors involved in Dutch outbreak responses. Then, the actors named and omitted by the participants were discussed. Results: An analysis of the FGs suggests that the Dutch citizens participating in the study were not fully aware of the scope of actors involved in the Dutch COVID-19 pandemic response. Some participants would have appreciated more information on the actors involved. This would help them have an informed opinion of the actors involved in the decision-making process, and accept non-pharmaceutical interventions implemented. Lastly, most participants recognised that they played a role in limiting the spread of the COVID-19 pandemic. Yet, very few spontaneously mentioned themselves as actors within the COVID-19 pandemic response. Conclusion: This study suggests that early in the COVID-19 pandemic, the Dutch citizens participating in this study's FG did not have a complete understanding of the scope of actors involved in the Dutch COVID-19 pandemic response, or the potential role of the citizen. Future research can build on these results to explore the citizen's perception of their role during PHEs of another origin, as well as other geographical and historical contexts. Patient or Public Contribution: The public participated in the focus groups and received a non-expert report summarising the outcomes of the focus groups.</p

First-principles calculation of magnetoelastic coefficients and magnetostriction in the spinel ferrites CoFe2O4 and NiFe2O4

We present calculations of magnetostriction constants for the spinel ferrites CoFe2O4 and NiFe2O4 using density functional theory within the GGA+U approach. Special emphasis is devoted to the influence of different possible cation distributions on the B site sublattice of the inverse spinel structure on the calculated elastic and magnetoelastic constants. We show that the resulting symmetry-lowering has only a negligible effect on the elastic constants of both systems as well as on the magnetoelastic response of NiFe2O4, whereas the magnetoelastic response of CoFe2O4 depends more strongly on the specific cation arrangement. In all cases our calculated magnetostriction constants are in good agreement with available experimental data. Our work thus paves the way for more detailed first-principles studies regarding the effect of stoichiometry and cation inversion on the magnetostrictive properties of spinel ferrites.Comment: 11 pages, 6 figure

Practice variation in home care nursing: mapping potential explanations through a scoping review of the literature

Needs assessment is the starting point of good home care as it determines which care is necessary, based on the needs of patients, their personal situation, and social context. There are indications that practice variation in needs assessment exists among home care nurses. However, little is known about potential explanations for this variation. Therefore, we explored potential explanations for practice variation in other areas and examined whether these explanations can be applied to explain variation in needs assessment in home care nursing. We conducted a scoping review of the literature on practice variation in (1) needs assessment in home care nursing, (2) home care nursing in general, and (3) medical care in general, with searches in PubMed and CINAHL. We assessed over 6,000 references. Ultimately, 386 studies were included. Explanations for practice variation were grouped into micro, meso and macro level. This scoping review provided insight into a wide variety of variables that might play a role in explaining practice variation in (needs assessment in) home care nursing, such as availability of guidelines, organisational culture, team norms, resources, and preferences of patients. However, the small literature on needs assessment by home care nurses devoted more attention to patients and their social context, compared to the literature on practice variation in general. We discuss how and to what extent these variables could relate to practice variation in (needs assessment in) home care nursing. Future research should empirically examine the role of these variables in explaining the observed practice variation

The pseudo‐brookite spin‐glass system studied by means of muon spin relaxation

Zero-field muon spin relaxation (µSR) experiments have been performed on the spin glass Fe1.75Ti1.25O5. Above the spin-glass temperature of 44 K a distinct exponential µSR rate (¿) is observed, while below Tg a square-root exponential decay occurs, indicating fast spin fluctuations. Near 8 K, a maximum in ¿ is indicative of transverse spin ordering. The low ¿ values and the sharp ¿ peak at Tg are very promising for the study of spin freezing models like the Vogel–Fulcher law or the power law