Local and nonlocal spin Seebeck effect in lateral Pt-Cr2O3\mathrm{Cr_2O_3}-Pt devices at low temperatures

We have studied thermally driven magnon spin transport (spin Seebeck effect, SSE) in heterostructures of antiferromagnetic $\alpha$-$\mathrm{Cr_2O_3}$ and Pt at low temperatures. Monitoring the amplitude of the local and nonlocal SSE signals as a function of temperature, we found that both decrease with increasing temperature and disappear above 100 K and 20 K, respectively. Additionally, both SSE signals show a tendency to saturate at low temperatures. The nonlocal SSE signal decays exponentially for intermediate injector-detector separation, consistent with magnon spin current transport in the relaxation regime. We estimate the magnon relaxation length of our $\alpha$-$\mathrm{Cr_2O_3}$ films to be around 500 nm at 3 K. This short magnon relaxation length along with the strong temperature dependence of the SSE signal indicates that temperature-dependent inelastic magnon scattering processes play an important role in the intermediate range magnon transport. Our observation is relevant to low-dissipation antiferromagnetic magnon memory and logic devices involving thermal magnon generation and transport.Comment: Accepted in APL Materials, For Supplementary Material see published versio

Nanoscale mechanics of antiferromagnetic domain walls

Antiferromagnets offer remarkable promise for future spintronics devices, where antiferromagnetic order is exploited to encode information. The control and understanding of antiferromagnetic domain walls (DWs) - the interfaces between domains with differing order parameter orientations - is a key ingredient for advancing such antiferromagnetic spintronics technologies. However, studies of the intrinsic mechanics of individual antiferromagnetic DWs remain elusive since they require sufficiently pure materials and suitable experimental approaches to address DWs on the nanoscale. Here we nucleate isolated, 180{\deg} DWs in a single-crystal of Cr$_2$O$_3$, a prototypical collinear magnetoelectric antiferromagnet, and study their interaction with topographic features fabricated on the sample. We demonstrate DW manipulation through the resulting, engineered energy landscape and show that the observed interaction is governed by the DW's elastic properties. Our results advance the understanding of DW mechanics in antiferromagnets and suggest a novel, topographically defined memory architecture based on antiferromagnetic DWs.Comment: 3 pages, 3 figures plus Supplementary Material. Questions and comments are welcom

Highly compliant planar Hall effect sensor with sub 200 nT sensitivity

Being a facet of flexible electronics, mechanically reshapeable magnetic field sensorics enable novel device ideas for soft robotics, interactive devices for virtual- and augmented reality and point of care diagnostics. These applications demand mechanically compliant yet robust sensor devices revealing high sensitivity to small magnetic fields. To push the detection limit of highly compliant and linear magnetic field sensors to be in the sub-µT range, we explore a new fundamental concept for magnetic field sensing, namely the planar Hall effect in magnetic thin films. With their remarkable bendability down to 1 mm, these compliant planar Hall effect sensors allow for an efficient detection of magnetic fields as small as 200 nT with a limit of detection of 20 nT. We demonstrate the application potential of these devices as a direction (angle) as well as proximity (distance) sensors of tiny magnetic fields emanating from magnetically functionalized objects. With their intrinsic linearity and simplicity of fabrication, these compliant planar Hall effect sensors have the potential to become a standard solution for low field applications of shapeable magnetoelectronics in point of care applications and on-skin interactive electronics.Fil: Granell, Pablo Nicolás. Instituto Nacional de Tecnología Industrial; Argentina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; ArgentinaFil: Wang, Guoliang. Institute of Ion Beam Physics and Materials Research; AlemaniaFil: Cañon Bermudez, Gilbert Santiago. Institute of Ion Beam Physics and Materials Research; AlemaniaFil: Kosub, Tobias. Institute of Ion Beam Physics and Materials Research; AlemaniaFil: Golmar, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; ArgentinaFil: Steren, Laura Beatriz. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Constituyentes | Comision Nacional de Energia Atomica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Constituyentes.; ArgentinaFil: Fassbender, Jürgen. Institute of Ion Beam Physics and Materials Research; AlemaniaFil: Makarov, Denys. Institute of Ion Beam Physics and Materials Research; Alemani

Purely antiferromagnetic magnetoelectric random access memory

Magnetic random access memory schemes employing magnetoelectric coupling to write binary information promise outstanding energy efficiency. We propose and demonstrate a purely antiferromagnetic magnetoelectric random access memory (AF-MERAM) that offers a remarkable 50-fold reduction of the writing threshold compared with ferromagnet-based counterparts, is robust against magnetic disturbances and exhibits no ferromagnetic hysteresis losses. Using the magnetoelectric antiferromagnet Cr2O3, we demonstrate reliable isothermal switching via gate voltage pulses and all-electric readout at room temperature. As no ferromagnetic component is present in the system, the writing magnetic field does not need to be pulsed for readout, allowing permanent magnets to be used. Based on our prototypes, we construct a comprehensive model of the magnetoelectric selection mechanisms in thin films of magnetoelectric antiferromagnets, revealing misfit induced ferrimagnetism as an important factor. Beyond memory applications, the AF-MERAM concept introduces a general all-electric interface for antiferromagnets and should find wide applicability in antiferromagnetic spintronics

Process evaluation in practice based research networks: a study protocol for a mixed-methods implementation study

Introduction: General practitioners often criticise clinical trials for their poor applicability in primary care, which may at least partially explain why their engagement in primary care research remains limited. In order to enhance primary care research, the German government has funded six regional practice based research networks (PBRNs). Within the Bavarian PBRN (BayFoNet), two cluster-randomised pilot trials will be conducted. This paper presents the protocol of the process evaluation accompanying both trials, which aims to explore relevance, feasibility, acceptability and credibility of clinical research in primary care from the perspectives of BayFoNet researchers, general practitioners, and patients. Methods and analysis: The BayFoNet will be established by recruiting general practices (GPs) as prospective research collaborators in two cluster randomised pilot trials. Research teams will provide training in good clinical practice, and support practices in patient recruitment, data collection and documentation. Our process evaluation explores barriers and facilitators in the set up of the BayFoNet PBRN and both cluster randomised pilot trials, under the application of the consolidated framework for implementation research and the theoretical domains framework. In a mixed-methods concept, we will use qualitative and quantitative approaches to evaluate both pilot cluster-randomised trials as well as the BayFoNet itself: focus groups with researchers, semi-structured interviews with general practitioners and questionnaires for patients participating in the pilot cluster-randomised trials at three different time points

Purely Antiferromagnetic Magnetoelectric Random Access Memory

Magnetic random access memory schemes employing magnetoelectric coupling to write binary information promise outstanding energy efficiency. We propose and demonstrate a purely antiferromagnetic magnetoelectric random access memory (AF-MERAM) that offers a remarkable 50 fold reduction of the writing threshold compared to ferromagnet-based counterparts, is robust against magnetic disturbances and exhibits no ferromagnetic hysteresis losses. Using the magnetoelectric antiferromagnet Cr2O3, we demonstrate reliable isothermal switching via gate voltage pulses and all-electric readout at room temperature. As no ferromagnetic component is present in the system, the writing magnetic field does not need to be pulsed for readout, allowing permanent magnets to be used. Based on our prototypes of these novel systems, we construct a comprehensive model of the magnetoelectric selection mechanism in thin films of magnetoelectric antiferromagnets. We identify that growth induced effects lead to emergent ferrimagnetism, which is detrimental to the robustness of the storage. After pinpointing lattice misfit as the likely origin, we provide routes to enhance or mitigate this emergent ferrimagnetism as desired. Beyond memory applications, the AF-MERAM concept introduces a general all-electric interface for antiferromagnets and should find wide applicability in purely antiferromagnetic spintronics devices.Comment: Main text (4 figures) + supplementary information (7 figures

Nanomagnetism of magnetoelectric granular thin-film antiferromagnets

Antiferromagnets have recently emerged as attractive platforms for spintronics applications, offering fundamentally new functionalities compared to their ferromagnetic counterparts. While nanoscale thin film materials are key to the development of future antiferromagnetic spintronics technologies, experimental tools to explore such films on the nanoscale are still sparse. Here, we offer a solution to this technological bottleneck, by addressing the ubiquitous surface magnetisation of magnetoelectic antiferromagnets in a granular thin film sample on the nanoscale using single-spin magnetometry in combination with spin-sensitive transport experiments. Specifically, we quantitatively image the evolution of individual nanoscale antiferromagnetic domains in 200-nm thin-films of Cr$_2$O$_3$ in real space and across the paramagnet-to-antiferromagnet phase transition. These experiments allow us to discern key properties of the Cr$_2$O$_3$ thin film, including the mechanism of domain formation and the strength of exchange coupling between individual grains comprising the film. Our work offers novel insights into Cr$_2$O$_3$'s magnetic ordering mechanism and establishes single spin magnetometry as a novel, widely applicable tool for nanoscale addressing of antiferromagnetic thin films.Comment: 22 pages, 7 figure