Scott Sommerfeldt Elected ASA President

Magnetic pyrochlores with non-Kramers rare-earth ions provide a platform for exploring emergent gauge physics and quantum spin-ice behavior, yet the influence of structural disorder on their ground states remains insufficiently understood. Here we combine bulk characterization and single-crystal neutron-scattering measurements to investigate the non-Kramers pyrochlore Pr2Sn2O7. At temperatures below ∼1 K, the system exhibits key hallmarks of quantum spin-ice physics, including anisotropic spin-ice correlations and two distinct dynamical timescales. Upon further cooling, however, we observe a complete spin-freezing transition at Tf≈0.15 K, accompanied by recovery of the full nuclear Schottky anomaly, the emergence of a gapped magnetic excitation, and the development of incipient (100) magnetic correlations. Comparison with related Pr-based pyrochlores places Pr2Sn2O7 near the spin-frozen boundary of a disorder-perturbed phase diagram. These results establish a disorder-driven framework for the evolution of quantum spin-ice behavior into frozen ground states, revealing how signatures of a proximate quantum spin liquid can persist despite disorder-induced spin freezing in non-Kramers pyrochlores.

Acoustic beamforming is widely used for source localization and line-of-bearing determination. Although many different beamforming techniques have been formulated, atmospheric turbulence effects on acoustic arrays are usually ignored in both their theoretical formulation and practical implementation. As a result, the performance of conventional beamformers, formulated for a non-turbulent atmosphere, degrades in the presence of wind velocity and temperature fluctuations, which cause fluctuations in the received signal amplitude and phase. This article presents a mathematical framework in which the amplitude and phase fluctuations are effectively suppressed from the signals allowing application of any beamforming technique and mitigating its performance degradation in a turbulent atmosphere. The framework is constrained to a single source and by the monochromatic plane wave approximation. Application of such an approach to an experiment revealed that the phase and amplitude fluctuations with spatial scales smaller than the array aperture are successfully suppressed, but the larger fluctuations (resulting in wavefront random tilt) remain and cause errors in the line of bearing estimates.

High-density multielectrode arrays (HD-MEAs) generate large, complex datasets that are challenging to efficiently manage and analyze with existing tools, especially in open-source environments. To address this, we developed the BYU Seizure and Analytics Tool (YSA), an open-source graphical user interface built in Python and C++ for efficient analysis and visualization of HD-MEA recordings. The YSA features raster plots, automated discharge detection and tracking, downsampling, playback, and export functions, enabling streamlined workflows for large-scale neural data. We demonstrate the utility of the tool in the context of seizure and status epilepticus-like activity, highlighting how the YSA facilitates rapid exploration of the spatiotemporal dynamics in brain networks. This platform provides an accessible and practical solution for HD-MEA data analysis, supporting a range of neuroscience applications.

Introduction: This study aims to explore the mechanical properties of porous microelectrodes formed from vertically aligned carbon nanotube (CNT) forests. Specifically, we investigate the range of effective CNT-based microelectrode (ME) moduli that can be fabricated and identify moduli within that range that significantly reduce strain on brain tissue during micromotion.Materials and methods: To address these questions, we developed a micromechanical measurement method, known as the dual deflection (DD) test, which is compatible with microelectrode array (MEA) form factors and can measure a wide range of moduli with a 30% uncertainty. Using the DD test with small deflections, we measured the effective Young’s modulus of freestanding CNT microelectrodes (MEs) fabricated with different carbon infiltration times (0, 15, and 30 s) at 900°C. We also developed a static 10 μm deflection finite element analysis (FEA) model to compare the brain tissue strain induced by probes with the maximum (1.7 GPa), median (72 MPa), and minimum (3.9 MPa) measured CNT moduli, along with the modulus of silicon (165 GPa) for comparison.Results: The DD test results showed mean effective moduli of 19.6 ± 14.5 MPa, 67.7 ± 22.7 MPa, and 168 ± 62.3 MPa for arrays fabricated with 0, 15, and 30 s infiltrations, respectively. The FEA model revealed that probes with the maximum CNT modulus induced similar strain to the silicon probes at the tip, while probes with the minimum and median CNT moduli showed minimal strain at the tip.Discussion: These findings suggest that CNT microelectrodes with moduli in the tens of MPa range, achievable through 15 s of carbon infiltration, can significantly reduce brain tissue strain. Additionally, we consistently observed that microelectrodes with 15 s of infiltration were apparently undamaged after deflection, making them mechanically promising candidates for neural probe arrays.

Double scheelite-type oxides of the form A+A′3+(WO4)2 are promising hosts for rare-earth-doped solid-state lasing materials. Using synchrotron X-ray and neutron powder diffraction with total scattering and pair distribution function analysis, the interplay between long-range symmetry and short-range distortions across the AA′(WO4)2 (A+ = Li, Na, K; A′3+ = La, Lu, Bi) series has been resolved. The Na- and La-containing oxides display an average tetragonal I41/a scheelite-type structure with disorder across the two A-site cations. Pronounced local-scale deviations arise from differences in A-site cation size, polarizability, and the presence of 6s2 lone pair activity, with symmetry-lowering required to model the bonding requirements of each (A/A′)O8 polyhedron. These requirements are better captured by the partial cation ordering and displacements allowed by a monoclinic I2 small-box model. When A+ = Li or K, the Lu-containing analogues order across the A site and display long-range symmetry lowering to nonscheelite monoclinic structures, consistent with the less polarizable LuO8 polyhedra. Reverse Monte Carlo modeling reveals an interplay between cation size and the polarizability of A-site cations, explaining and establishing structural design principles for tuning local environments and optimizing emission bandwidths in scheelite-based solid-state laser hosts.

Magnetostructural coupling plays a crucial role in numerous types of quantum materials and functional magnetic materials. Here, we investigate the magnetostructurally active ferromagnet MnSb, whose derivative compounds Mn_1+xSb are strong candidates for magnetocaloric applications. We reveal an unusually large spontaneous magnetostriction effect in MnSb, resulting in a relative unit cell expansion of up to 1% and an extended temperature region of negative thermal expansion of the crystallographic axis. This magnetovolume effect is exceptional not only because of its magnitude, but also because the volume increase begins in the paramagnetic phase and exhibits unconventional linear scaling with the short-range ferromagnetic correlations as the temperature is lowered, before switching to quadratic scaling with the long-range-ordered magnetic moment below the transition. We explain this exceptional behavior through unusual trilinear couplings among the lattice strain and domains of distinct magnetic order parameters. Heat capacity measurements also provide new thermodynamic information about MnSb, including determination of the Debye and Einstein temperatures to be 164 and 296 K, respectively. These findings greatly expand our understanding of MnSb and provide insights into the fundamental materials physics of magnetostructural coupling in the presence of short-range magnetic correlations, with potential for broad applicability.