Voltage-controlled nonvolatile isothermal spin state switching of a Fe{H2B(pz)2}2(bipy) (pz = tris(pyrazol-1–1y)-borohydride, bipy = 2,2′-bipyridine) film, more than 40 to 50 molecular layers ...thick, is possible when it is adsorbed onto a molecular ferroelectric substrate. Accompanying this high-spin and low-spin state switching, at room temperature, we observe a remarkable change in conductance, thereby allowing not only nonvolatile voltage control of the spin state (“write”) but also current sensing of the molecular spin state (“read”). Monte Carlo Ising model simulations of the high-spin state occupancy, extracted from X-ray absorption spectroscopy, indicate that the energy difference between the low-spin and high-spin state is modified by 110 meV. Transport measurements demonstrate that four terminal voltage-controlled devices can be realized using this system.
Abstract
In this work, we provide clear evidence of magnetic anisotropy in the local orbital moment of a molecular thin film based on the SCO complex Fe(H
2
B(pz)
2
)
2
(bipy) (pz = pyrazol−1−yl, ...bipy = 2,2′−bipyridine). Field dependent x-ray magnetic circular dichroism measurements indicate that the magnetic easy axis for the orbital moment is along the surface normal direction. Along with the presence of a critical field, our observation points to the existence of an anisotropic energy barrier in the high-spin state. The estimated nonzero coupling constant of ∼2.47 × 10
−5
eV molecule
−1
indicates that the observed magnetocrystalline anisotropy is mostly due to spin–orbit coupling. The spin- and orbital-component anisotropies are determined to be 30.9 and 5.04 meV molecule
−1
, respectively. Furthermore, the estimated
g
factor in the range of 2.2–2.45 is consistent with the expected values. This work has paved the way for an understanding of the spin-state-switching mechanism in the presence of magnetic perturbations.
The X-ray-induced spin crossover transition of an Fe (II) molecular thin film in the presence and absence of a magnetic field has been investigated. The thermal activation energy barrier in the soft ...X-ray activation of the spin crossover transition for Fe{H2B(pz)2}2(bipy) molecular thin films is reduced in the presence of an applied magnetic field, as measured through X-ray absorption spectroscopy at various temperatures. The influence of a 1.8 T magnetic field is sufficient to cause deviations from the expected exponential spin state transition behavior which is measured in the field free case. We find that orbital moment diminishes with increasing temperature, relative to the spin moment in the vicinity of room temperature.
For the spin crossover coordination polymer Fe(L1)(bipy)
n
(where L1 is a N
2
O
2
2−
coordinating Schiff base-like ligand bearing a phenazine fluorophore and bipy = 4,4′-bipyridine), there is ...compelling additional evidence of a spin state transition. Both Fe 2p X-ray absorption and X-ray core level photoemission spectroscopies confirm that a spin crossover takes place, as observed by magnetometry. Yet the details of the temperature dependent changes of the spin state inferred from both X-ray absorption and X-ray core level photoemission, differ from magnetometry, particularly with regard to the apparent critical transition temperatures and the cooperative nature of the curve progression in general. Comparing the experimental spin crossover data to Ising model simulations, a transition activation energy in the region of 160 to 175 meV is indicated, along with a nonzero exchange
J
. Overall, the implication is that there may be perturbations to the bistability of spin states, that are measurement dependent or that the surface differs from the bulk with regard to the cooperative effects observed upon spin transition.
For the spin crossover coordination polymer Fe(L1)(bipy)
n
(where L1 is a N
2
O
2
2−
coordinating Schiff base-like ligand bearing a phenazine fluorophore and bipy = 4,4′-bipyridine), there is compelling additional evidence of a spin state transition.
Nonvolatile, molecular multiferroic devices have now been demonstrated, but it is worth giving some consideration to the issue of whether such devices could be a competitive alternative for ...solid-state nonvolatile memory. For the Fe (II) spin crossover complex Fe{H2B(pz)2}2(bipy), where pz = tris(pyrazol-1-yl)-borohydride and bipy = 2,2′-bipyridine, voltage-controlled isothermal changes in the electronic structure and spin state have been demonstrated and are accompanied by changes in conductance. Higher conductance is seen with Fe{H2B(pz)2}2(bipy) in the high spin state, while lower conductance occurs for the low spin state. Plausibly, there is the potential here for low-cost molecular solid-state memory because the essential molecular thin films are easily fabricated. However, successful device fabrication does not mean a device that has a practical value. Here, we discuss the progress and challenges yet facing the fabrication of molecular multiferroic devices, which could be considered competitive to silicon.
Current state-of-the-art Artificial Intelligence (AI) anomaly detection from images is primarily used for defect detection and relies on relatively homogeneous datasets of images with similar ...foregrounds and backgrounds. This type of anomaly detection uses human labelled ground-truth data. In our research, we have extremely heterogeneous datasets and want to identify outliers. We use self-supervised Variational Autoencoders (VAEs) to identify anomalies in the latent vector feature space. Understanding the outliers in a large training data set is important for establishing trustworthiness of the AI models learned from these data, a strong requirement for military AI applications. Our study uses 8984 examples from Kaggle military planes and 4300 examples from Kaggle landscape data. We present the results of the combined heterogeneous dataset on the localized methods, with one such result exhibiting inliers as landscapes/backgrounds and outliers as all aircraft, detecting aircraft as anomalies with a 0.87 AUC. Results also include the inter-class AUC across the different aircraft classes. Our contribution to the state-of-the-art is to apply isolation forests to the latent space data after UMAP embeddings in a strongly heterogeneous image dataset for military applications to identify anomalies.
The introduction of animals into school classrooms has been posited as a beneficial intervention for individuals with Autism Spectrum Disorder (ASD). Whilst evidence that animal-assisted ...interventions or activities can positively influence classroom behaviour and learning outcomes is emerging, little is known about the experiences and attitudes of those who implement it. We presented a series of open and close-ended questions via an online survey to Australian school teachers working with students on the autistic spectrum. Whether teachers had experienced companion animals in the classroom or not, companion animals were believed to provide a means for improving social skills and engagement within the classroom, as well as decreasing stress, anxiety, and the occurrence of problematic behaviours. Yet, despite an overall positive attitude, and 68% having had animals or pets in their classroom, only 16% of respondents had experience with ‘formal’ animal-assisted interventions. Explanations for why both formal and informal animal-assisted interventions were either not being adopted, or was not currently being considered, included a lack of knowledge, lack of support and resources, reactions of the student in relation to allergies and behaviour, and issues relating to animal welfare. It was also acknowledged that the evidence-base for animal-assisted interventions for students with ASD is currently lacking, and that such interventions were not suitable for all students, or all classroom situations. Moving forward, it is important that the inclusion of companion animals and more formal based animal intervention programs in classrooms be adequately designed and evaluated, because implementing or promoting time consuming and financially costly strategies without the evidence is problematic.
Inflammatory lesions in the brain activate a systemic acute-phase response (APR), which is dependent on the release of extracellular vesicles (EVs) into the circulation. The resulting APR is ...responsible for regulating leukocyte mobilization and subsequent recruitment to the brain. Factors that either exacerbate or inhibit the APR will also exacerbate or inhibit central nervous system (CNS) inflammation as a consequence and have the potential to influence ongoing secondary damage. Here, we were interested to discover how the circulating EV population changes after traumatic brain injury (TBI) and how manipulation of the circulating EV pool impacts on the outcome of TBI. We found the number of circulating EVs increased rapidly post-TBI, and this was accompanied by an increase in CNS and hepatic leukocyte recruitment. In an adoptive transfer study, we then evaluated the outcomes of TBI after administering EVs derived from either in vitro macrophage or endothelial cell lines stimulated with lipopolysaccharide (LPS), or from murine plasma from an LPS challenge using the air-pouch model. By manipulating the circulating EV population, we were able to demonstrate that each population of transferred EVs increased the APR. However, the characteristics of the response were dependent on the nature of the EVs; specifically, it was significantly increased when animals were challenged with macrophage-derived EVs, suggesting that the cellular origins of EVs may determine their function. Selectively targeting EVs from macrophage/monocyte populations is likely to be of value in reducing the impact of the systemic inflammatory response on the outcome of traumatic CNS injury.
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