Dimensional Evolution of Spin Correlations in the Magnetic Pyrochlore Yb2Ti2O7

The pyrochlore material Yb2Ti2O7 displays unexpected quasi-two-dimensional (2D) magnetic correlations within a cubic lattice environment at low temperatures, before entering an exotic disordered ground state below T=265mK. We report neutron scattering measurements of the thermal evolution of the 2D spin correlations in space and time. Short range three dimensional (3D) spin correlations develop below 400 mK, accompanied by a suppression in the quasi-elastic (QE) scattering below ~ 0.2 meV. These show a slowly fluctuating ground state with spins correlated over short distances within a kagome-triangular-kagome (KTK) stack along [111], which evolves to isolated kagome spin-stars at higher temperatures. Furthermore, low-temperature specific heat results indicate a sample dependence to the putative transition temperature that is bounded by 265mK, which we discuss in the context of recent mean field theoretical analysis.Comment: 5 pages, 6 figure

Impacting Children’s Physical and Mental Health through Kinesiology Support in Clinical Care: A Randomized Controlled Trial Protocol

Objectives To enhance the confidence of children and adolescents with medical conditions and disabilities to engage in healthy, active lifestyles. Children with medical conditions and disabilities often exhibit more sedentary lifestyles relative to peers and are at increased risk of poor health outcomes. Clinical experience suggests physical activity confidence is an important factor influencing physical activity participation. Methods This randomized controlled trial evaluates an evidence-based intervention targeting physical activity confidence among children and adolescents with medical conditions and disabilities. Potential participants, 8 to 18 years of age diagnosed with a medical condition or disability, will be screened for adequate physical activity motivation but a lack confidence. Consenting participants (n=128) will be randomized 1:1 to a 12-week in-person or virtual physical activity intervention (24 hours/week total) led by a Registered Kinesiologist or control (assessments only). The intervention will combine physical activity participation with education about physical activity knowledge, goal setting, motivation and self-management. Primary outcomes are self-reported physical activity confidence and motivation at baseline, post-intervention and three months following intervention completion. A secondary outcome will be daily physical activity minutes assessed by accelerometry. A repeated measures mixed model will be used to compare outcomes between the in-person intervention, virtual intervention, and control groups (alpha=0.05). Conclusions This trial aims to assess the impact of a novel application of behaviour change theory on physical activity confidence among children and adolescents living with medical conditions or disabilities. Increased physical activity confidence, knowledge and skills could enable these youth to lead a more active lifestyle

Far-from-equilibrium monopole dynamics in spin ice

Condensed matter in the low-temperature limit reveals exotic physics associated with unusual orders and excitations, with examples ranging from helium superfluidity1 to magnetic monopoles in spin ice2, 3. The far-from-equilibrium physics of such low-temperature states may be even more exotic, yet to access it in the laboratory remains a challenge. Here we demonstrate a simple and robust technique—the ‘magnetothermal avalanche quench’—and its use in the controlled creation of non-equilibrium populations of magnetic monopoles in spin ice at millikelvin temperatures. These populations are found to exhibit spontaneous dynamical effects that typify far-from-equilibrium systems and yet are captured by simple models. Our method thus opens new directions in the study of far-from-equilibrium states in spin ice and other exotic magnets