On the estimation of temporal mileage rates

Peer reviewedPostprin

Torque magnetometry study of the spin reorientation transition and temperature-dependent magnetocrystalline anisotropy in NdCo5

We present the results of torque magnetometry and magnetic susceptibility measurements to study in detail the spin reorientation transition (SRT) and magnetic anisotropy in the permanent magnet NdCo5. We further show simulations of the measurements using first-principles calculations based on density-functional theory and the disordered local moment picture of magnetism at finite temperatures. The good agreement between theory and experimental data leads to a detailed description of the physics underpinning the SRT. In particular we are able to resolve the magnetization of, and to reveal a canting between, the Nd and Co sublattices. The torque measurements carried out in the ac and ab planes near the easy direction allow us to estimate the anisotropy constants, K 1, K 2 and K 4 and their temperature dependences. Torque curves, τ(γ) recorded by varying the direction of a constant magnetic field in the crystallographic ac plane show a reversal in the polarity as the temperature is changed across the SRT (240 < T < 285 K). Within this domain, τ(γ) exhibits unusual features different to those observed above and below the transition. The single crystals of NdCo5 were grown using the optical floating zone technique

Comparative study of the centrosymmetric and non-centrosymmetric superconducting phases of Re3W using muon-spin spectroscopy and heat capacity measurements

We compare the low-temperature electronic properties of the centrosymmetric (CS) and non-centrosymmetric (NCS) phases of Re3W using muon-spin spectroscopy and heat capacity measurements. The zero-field muSR results indicate that time-reversal symmetry is preserved for both structures of Re3W. Transverse-field muon spin rotation has been used to study the temperature dependence of the penetration depth lambda(T) in the mixed state. For both phases of Re3W, lambda(T) can be explained using a single-gap s-wave BCS model. The magnetic penetration depth at zero temperature, lambda(0), is 164(7) and 418(6) nm for the centrosymmetric and the non-centrosymmetric phases of Re3W respectively. Low-temperature specific heat data also provide evidence for an s-wave gap-symmetry for the two phases of Re3W. Both the muSR and heat capacity data show that the CS material has a higher Tc and a larger superconducting gap Delta(0) at 0 K than the NCS compound. The ratio Delta(0)/kBTc indicates that both phases of Re3W should be considered as strong-coupling superconductors.Comment: 7 pages, to appear in Physical Review

Tunability of the spin reorientation transitions with pressure in NdCo5

We present pressure-dependent magnetization measurements carried out in the domain of the spin reorientation transitions (SRTs) of a NdCo5 single crystal. The application of a hydrostatic pressure leads to a shift in the SRTs to higher temperatures. This shift is found to be very sensitive to pressure, with the SRT temperatures increasing at a rate of ≈17 K/GPa. To explain the experimental results, we have also performed first-principles calculations of the SRT temperatures for different applied strains, which corroborate the experimental findings. The calculations attribute the pressure dependence of the SRTs to a faster weakening of the Co contribution to the magnetocrystalline anisotropy with pressure compared to the Nd contribution

Superconducting and magnetic properties of Sr3Ir4Sn13

Magnetization and muon spin relaxation or rotation (muSR) measurements have been performed to study the superconducting and magnetic properties of Sr3Ir4Sn13. From magnetization measurements the lower and upper critical fields of Sr3Ir4Sn13 are found to be 81(1) Oe and 14.4(2) kOe, respectively. Zero-field muSR data show no sign of any magnetic ordering or weak magnetism in Sr3Ir4Sn13. Transverse-field muSR measurements in the vortex state provided the temperature dependence of the magnetic penetration depth. The dependence of penetration depth with temperature is consistent with the existence of single s-wave energy gap in the superconducting state of Sr3Ir4Sn13 with a gap value of 0.82(2) meV at absolute zero temperature. The magnetic penetration depth at zero temperature is 291(3) nm. The gap to Tc ratio is 2.1(1), indicates that Sr3Ir4Sn13 should be considered as a strong-coupling superconductor.Comment: 6 pages, 5 figure

Observation of magnetic fragmentation in spin ice

Fractionalised excitations that emerge from a many body system have revealed rich physics and concepts, from composite fermions in two-dimensional electron systems, revealed through the fractional quantum Hall effect, to spinons in antiferromagnetic chains and, more recently, fractionalisation of Dirac electrons in graphene and magnetic monopoles in spin ice. Even more surprising is the fragmentation of the degrees of freedom themselves, leading to coexisting and a priori independent ground states. This puzzling phenomenon was recently put forward in the context of spin ice, in which the magnetic moment field can fragment, resulting in a dual ground state consisting of a fluctuating spin liquid, a so-called Coulomb phase, on top of a magnetic monopole crystal. Here we show, by means of neutron scattering measurements, that such fragmentation occurs in the spin ice candidate Nd$_2$Zr$_2$O$_7$. We observe the spectacular coexistence of an antiferromagnetic order induced by the monopole crystallisation and a fluctuating state with ferromagnetic correlations. Experimentally, this fragmentation manifests itself via the superposition of magnetic Bragg peaks, characteristic of the ordered phase, and a pinch point pattern, characteristic of the Coulomb phase. These results highlight the relevance of the fragmentation concept to describe the physics of systems that are simultaneously ordered and fluctuating.Comment: accepted in Nature Physic

Interviewer: 'Are women and girls ever responsible for the domestic violence they encounter?' Student: 'No, well, unless they did something really, really bad …'

Research shows the ‘gendered nature’ of domestic violence, with Women’s Aid (a UK-based charity) estimating that 1 in 4 women are affected (2014). This paper reports on a project - funded by Comic Relief, completed by Nottinghamshire Domestic Violence Forum (now known as Equation) and evaluated by Nottingham Trent University. The project adopts a Whole School Approach in seeking to prevent domestic violence. Students at three secondary schools attended between one and five blocks of work, and special events. There is evidence of positive developments - with young people showing understanding of domestic violence as well as the margins between healthy and unhealthy relationships. However, not all students could reply ‘never’ to the question of ‘are women and girls to blame for the domestic violence they experience?’, remarking that if the woman had done something ‘really, really bad’ then violence might be justified. We argue that young people’s uncertainties need to be situated within the gender-unequal socio-contexts of contemporary society, and further call for a WSA to domestic violence prevention to be a compulsory part of the UK national curriculum

Acute cardiovascular changes in women undergoing in vitro fertilisation (IVF), a systematic review and meta-analysis

Objectives: Ovarian stimulation during fertility treatment leads to profound maternal physiological changes. Women undergoing in vitro fertilisation (IVF) may be at an increased risk of future cardiovascular morbidity, though little is known about the effects on maternal cardiovascular function. We aim to systematically review whether IVF treatment is associated with changes in maternal haemodynamic parameters, and the effects of different protocols. Study Design: A systematic review and meta-analysis of English language studies identified on Medline and EMBASE database, between 1978, to 2019. Search terms: IVF, maternal haemodynamics, and cardiovascular. Studies reporting on ovulation induction, intrauterine insemination, and oocyte donation were excluded. Methodological quality was assessed by using the adapted Critical Appraisal Skills Programme (CASP) checklist. A meta-analysis was conducted for blood pressure and heart rate on patients undergoing the long GnRH agonist protocol according to Cochrane guidelines. We considered four time points in the IVF cycle, in chronological order: pre-treatment, pituitary down regulation, peak oestradiol and the luteal phase. Results: Nine suitable studies were identified; four fulfilled the criteria for meta-analysis. Two studies measuring heart rate found a significant increase in heart rate from pituitary down-regulation to peak estradiol levels, which was supported by the meta-analysis (3.78 \ub1 2.18 (p= < 0.0001)). Three studies reported a significant decrease in blood pressure from baseline, with those suitable for meta-analysis showing a significant decrease in mean arterial pressure (-2.08 \ub1 1.79 (p= < 0.0001)). Cardiac functional changes were reported for all studies and the changes depended on the type of protocol used. Conclusions: In Vitro Fertilisation leads to acute changes in maternal haemodynamics at different time points of the stimulation protocol. We found an increase in heart rate from pituitary down-regulation to peak estradiol levels and a significant decrease in blood pressure from baseline or pituitary down-regulation to the luteal phase. Cardiac functional changes were reported for all studies on the agonist protocol, but no significant changes were found using the antagonist protocol. It remains unclear as to whether these acute changes were associated with pregnancy complications or chronic cardiovascular sequelae