Christy John Kinane

Altermagnets, which combine antiferromagnetic-like magnetic compensation with ferromagnetic-like broken time-reversal symmetry, hold great promise for high-density and ultrafast spintronic applications. However, the detection and switching of perpendicular altermagnetic order are fundamentally constrained by magnetic symmetry, restricting both fundamental studies and practical implementation. Here we demonstrate the robust electrical reading and deterministic switching of perpendicular altermagnetic order by designing a Dirac semimetal/altermagnet heterostructure of PtTe₂/CrSb. This engineered interface enables anomalous Hall read-out via the altermagnetic proximity effect and delivers efficient spin–orbit torque for manipulating the epitaxial perpendicular Néel vector in CrSb. These findings substantially broaden the functional scope of altermagnetic heterostructures and pave the way for scalable altermagnetic memory.

In this study we use Fisher information within the software HOGBEN to optimize the structure of magnetic reference layers to maximize the information gained from polarized neutron reflectometry (PNR) measurements on soft-matter and biological samples. Our approach is based on simulating the reflectivity from an experimentally determined dataset of a supported lipid bilayer. A set of reflectivity curves is calculated by varying parameters associated with the substrate assembly containing a magnetic reference layer. For each of the calculated reflectivity curves, we quantified the sensitivity of the simulated data to the sample structure. Our Fisher information analysis predicts that decreasing the thickness of the capping layer combined with increasing the magnetic scattering length density of the magnetic reference layer will reduce measurement time of similar PNR experiments by up to a factor of 5.6 or, equivalently, reduce parameter uncertainties at fixed beam time by the same factor relative to the reference experiment. Within a practically realizable SiO ₂ capping layer window of 200–400 Å, the predicted gain remains substantial ( G ≈ 2.7). Because the parameters determining reflectivity curves are often correlated, such information is difficult to obtain in any other way. Experimental validation of these predictions on substrate assemblies synthesized according to the proposed designs is the natural next step. We established a theoretical method that can also be implemented within the context of other neutron reflectometry experiment. The approach allows the optimization of PNR experiments and will enable more straightforward and robust extraction of relevant parameters as well as more efficient use of neutron beam time.

Neutron reflectometry (NR) at the ISIS Neutron and Muon Source has evolved into a mature, versatile technique for investigating the structure and dynamics of interfaces across a wide range of scientific disciplines, including soft matter, magnetism, quantum materials and environmental systems. This article provides a comprehensive overview of the current instrumentation available at ISIS, detailing the capabilities of the four operational reflectometers – OFFSPEC, INTER, POLREF and SURF – including their time-of-flight configurations, scattering geometries, polarization options and range of accessible sample environments. Special emphasis is placed on the integration of advanced sample environments, automated control software and data analysis tools, including IBEX , MANTID and the ISIS Data Analysis as a Service ( IDAaaS ) platform, which collectively facilitate efficient, reproducible and high-quality NR measurements. Representative scientific highlights demonstrate the unique potential of NR to resolve sub-nanometre structural and kinetic information in biological membranes, thin functional films, quantum fluids and environmental interfaces. By consolidating detailed technical information, operational characteristics and examples of cutting-edge research, this article serves as a practical guide for new and experienced users, helping them design experiments, select suitable instruments and sample environments, and fully exploit the capabilities of ISIS neutron reflectometers.

Compositionally-graded amorphous rare earth:transition metal ferrimagnetic thin films offer exciting potential for enabling field-free spin-orbit torque (SOT) switching in spintronic devices. Vertical compositional gradients have previously been developed to enhance SOT efficiency via a proposed transition from out-of-plane (OOP) to in-plane (IP) magnetization to induce Dzyaloshinskii-Moriya interaction that breaks inversion symmetry within the layer. Here, we directly mapped the magnetization orientations within compositionally-graded GdCoFe layers by probing the depth-dependent local effective Gd-magnetization or the local net magnetization using X-ray and neutron reflectivity (PNR), respectively. These methods showed contrast between IP and OOP magnetization zones through the film thicknesses and PNR showed the magnetization compensation point within a graded GdCoFe layer. Transitions from IP to OOP magnetization depended on the local composition, and it was observed that some of these changes do not agree with expectations from the study of films with uniform composition. These results give the spatial distribution of magnetization and hence the anisotropy, essential for understanding and optimising field-free SOT switching.