Extrinsic Domain Research Articles

Advancing piezoelectricity and excellent thermal stability: -textured 0.75BF–0.25BT lead-free ceramics for high temperature applications

There is an urgent need for piezoelectric materials possessing both high piezoelectric properties and good thermal stability to facilitate the advancement of high temperature piezoelectric devices. However, conventional strategy for enhancing piezoelectricity via chemical modifications often comes at the cost of thermal stability due to a drop in Curie temperatures. In this study, we achieved remarkable results in <001>-oriented 0.75BiFeO3–0.25BaTiO3 (0.75BF–0.25BT) lead-free textured ceramics. These textured ceramics exhibit a high Curie temperatures Tc of 552 °C, large piezoelectric coefficients d33 of 265 pC/N, and exceptional piezoelectric thermal stability, with minimal variation of 8% across temperature from 25 °C to 300 °C. Compared to randomly oriented ceramics, the piezoelectric coefficient is about 2.5 times higher, marking it as one of the highest reported value for ceramics with Tc near 550 °C. The enhanced piezoelectric properties can be ascribed to improvements in both intrinsic lattice distortions and extrinsic non-180o domain motions, while the excellent piezoelectric thermal stability is attributed to the stable domain texture. These superior properties of the studied textured 0.75BF–0.25BT ceramics position them as competitive lead-free candidates for high-temperature piezoelectric applications.

Effects of quenching on domain switching and electric field-induced phase transformations in Na0.5Bi0.5TiO3-NaNbO3 ceramics

Quenching from high temperatures has been identified as a useful means to enhance the piezoelectric properties and thermal stability of bismuth-based perovskite ferroelectrics. In the present work, it is demonstrated that quenching leads to improvement of depolarization temperature, ferroelectric and piezoelectric properties in Na0.5Bi0.5TiO3-NaNbO3 (NBT-0.1NN) ceramics. In-situ synchrotron x-ray diffraction measurements indicated an irreversible transformation from cubic to coexisting cubic and rhombohedral phases during the application of a high electric field, for both as-sintered and quenched ceramics. These results confirm the non-ergodic relaxor ferroelectric nature of the materials. DC poling induced a transformation to single-phase rhombohedral structure in both cases, with highly textured domain configurations. These well-oriented ferroelectric domain states were relatively stable under subsequent bipolar electric field cycling. For the pre-poled NBT-0.1NN ceramics, the quenched samples were found to exhibit the highest intrinsic (lattice strain) and extrinsic (domain switching) contributions to electrostrain, due to the increased rhombohedral distortion.

Acceptor doping and actuation mechanisms in Sr-doped BiFeO3[sbnd]BaTiO3 ceramics

BiFeO3-BaTiO3 (BF-BT) ceramics are important multiferroic materials, which are attracting significant attention for potential applications in high temperature lead-free piezoelectric transducers. In the present study, the effects of Sr2+ as an acceptor dopant for Bi3+, in the range from 0 to 1.0% (in mole), on the structure and ferroelectric/piezoelectric properties of 0.7BiFeO3-0.3BaTiO3 ceramics were evaluated. The use of a post-sintering Ar annealing process was found to be an effective approach to reduce electrical conductivity induced by the presence of electron holes associated with reoxidation during cooling. A low Sr dopant concentration (0.3%, in mole) yielded enhanced ferroelectric (Pmax ∼ 0.37 C/m2, Pr ∼ 0.30 C/m2) and piezoelectric (d33 ∼ 178 pC/N, kp ∼ 0.27) properties, whereas higher levels led to chemically heterogeneous core-shell structures and secondary phases with an associated decline in performance. The electric field-induced strain of the Sr-doped BF-BT ceramics was investigated using a combination of digital image correlation macroscopic strain measurements and in-situ synchrotron X-ray diffraction. Quantification of the intrinsic (lattice strain) and extrinsic (domain switching) contributions to the electric field induced strain indicated that the intrinsic contribution dominated during the poling process.

Structural mechanisms of large piezoelectric responses in BiFeO3-PbTiO3 based solid-solution ceramics

Achieving large piezoelectric response and high Curie temperature, simultaneously, are of great demand but have been rarely achieved in BiFeO3-PbTiO3 (BF-PT) based morphotropic phase boundary (MPB) systems. In this work, in-situ synchrotron x-ray diffraction and transmission electron microscopy were carried out in BF-PT-0.19Ba(Zr,Ti)O3 high-temperature piezoceramic, a recently reported MPB composition with high piezoelectric coefficient, to elucidate the underlying structural mechanism. A field induced irreversible transition from tetragonal (T) P4mm phase to rhombohedral (R) R3c phase is identified although R and T phases are still coexisted after poling. This induces the significantly enhanced irreversible domain switching of both R and T phases and the reversible domain switching of R phase but only a slightly enhanced reversible switching of T phase of as compared with other BF-PT-x Ba(Zr,Ti)O3 MPB compositions, leading to the significant increase of lattice strain up to ∼0.15% but only a slightly increase of strain from extrinsic domain switching due to the strong coupling between lattice strain and domain switching in both R and T phases, although the strain contribution seems to be composition independent after the field induced irreversible phase transition. The present study demonstrates a new performance enhancement mechanism to design the high-performance BF-PT based high-temperature piezoelectric ceramics in terms of the different roles of R and T phases within MPB.

Domain-Aware Dual Attention for Generalized Medical Image Segmentation on Unseen Domains.

Recently, there has been significant progress in medical image segmentation utilizing deep learning techniques. However, these achievements largely rely on the supposition that the source and target domain data are identically distributed, and the direct application of related methods without addressing the distribution shift results in dramatic degradation in realistic clinical environments. Current approaches concerning the distribution shift either require the target domain data in advance for adaptation, or focus only on the distribution shift across domains while ignoring the intra-domain data variation. This paper proposes a domain-aware dual attention network for the generalized medical image segmentation task on unseen target domains. To alleviate the severe distribution shift between the source and target domains, an Extrinsic Attention (EA) module is designed to learn image features with knowledge originating from multi-source domains. Moreover, an Intrinsic Attention (IA) module is also proposed to handle the intra-domain variation by individually modeling the pixel-region relations derived from an image. The EA and IA modules complement each other well in terms of modeling the extrinsic and intrinsic domain relationships, respectively. To validate the model effectiveness, comprehensive experiments are conducted on various benchmark datasets, including the prostate segmentation in magnetic resonance imaging (MRI) scans and the optic cup/disc segmentation in fundus images. The experimental results demonstrate that our proposed model effectively generalizes to unseen domains and exceeds the existing advanced approaches.

Applying systems thinking to unravel the mechanisms underlying orthostatic hypotension related fall risk

Orthostatic hypotension (OH) is an established and common cardiovascular risk factor for falls. An in-depth understanding of the various interacting pathophysiological pathways contributing to OH-related falls is essential to guide improvements in diagnostic and treatment opportunities. We applied systems thinking to multidisciplinary map out causal mechanisms and risk factors. For this, we used group model building (GMB) to develop a causal loop diagram (CLD). The GMB was based on the input of experts from multiple domains related to OH and falls and all proposed mechanisms were supported by scientific literature. Our CLD is a conceptual representation of factors involved in OH-related falls, and their interrelatedness. Network analysis and feedback loops were applied to analyze and interpret the CLD, and quantitatively summarize the function and relative importance of the variables. Our CLD contains 50 variables distributed over three intrinsic domains (cerebral, cardiovascular, and musculoskeletal), and an extrinsic domain (e.g., medications). Between the variables, 181 connections and 65 feedback loops were identified. Decreased cerebral blood flow, low blood pressure, impaired baroreflex activity, and physical inactivity were identified as key factors involved in OH-related falls, based on their high centralities. Our CLD reflects the multifactorial pathophysiology of OH-related falls. It enables us to identify key elements, suggesting their potential for new diagnostic and treatment approaches in fall prevention. The interactive online CLD renders it suitable for both research and educational purposes and this CLD is the first step in the development of a computational model for simulating the effects of risk factors on falls.

Goal Contents, State Empathy and Instructional Goals in a Physical Disability Vignette

ABSTRACT Setting and recommending instructional goals represents an important communication process in educational and health domains, which are intersected in many cases. However, little is known about the antecedents of instructional goals. The aim of the present study was to examine how the contents of participants’ personal goals in life (i.e. goal contents) and state empathy during message processing affected the processes of prioritizing instructional goals in the case of an adolescent who presented physical disability and impaired cognitive functioning, as presented in a video vignette. Health and care practitioners who were members of the educational system, in-service teachers and university students of disciplines related to health, rehabilitation or education, participated in a cross-sectional study. The findings showed that the participants proposed instructional goals according to their current goal contents and state empathy. In particular, state empathy demonstrated both main effects and mediations in influencing intrinsic instructional goals. However, state empathy, in fact its associative component, influenced an extrinsic goal domain as well. Interpretations of this phenomenon are presented, and the limitations of some tools are demonstrated. In addition, suggestions are put forward regarding implications and future research for a proximal causation of the instructional goals.

Identifying the barriers of smoking cessation and predictors of nicotine dependence among adult Malaysian smokers: A cross-sectional study.

Proper understanding of the prevalence and determinants of nicotine dependence is crucial for developing and implementing effective tobacco control interventions. The aim of the study was to identify the intrinsic and extrinsic barriers to smoking cessation, and to assess the association between nicotine dependence with demographic variables in Malaysia. A cross-sectional survey based on the Challenges to Stopping Smoking Scale (CSS-21) and Fagerström test for nicotine dependence (FTND) was performed on smoking Malaysian citizens aged ≥18 years, from February to June 2021. A total of 1026 parents responded to the survey. As for the smoking dependence based on FTND, 39.1% suffered low-moderate dependence, while about 33.6% suffered moderate dependence. Only 1.8% suffered high dependence. Considering the barriers of quitting smoking based on CSS-21, the mean score of the intrinsic barriers domain was 5.7 ± 2.9, and for the extrinsic domain was 7.4 ± 4.0. The most common barrier reported in the intrinsic domain was the easy availability of cigarettes (69.8%), followed by experiencing withdrawal symptoms (68.5%). On the other hand, the most common barrier reported in the extrinsic domain was the belief in the capability of stopping smoking in the future (72.8%), followed by the fear of having side effects after stopping smoking (63.2%). Gender, race, education level, occupation, marital status, place of residence, and monthly income were also significantly associated with the FTND nicotine dependence category (all p<0.05). Pearson correlation analysis reported a positive association between intrinsic score (r=0.38), extrinsic score (r=0.43) and FTND score (all p<0.001). Barriers to stopping smoking should be taken into consideration in initiatives to decrease smoking-related mortality. Vulnerable populations that are susceptible to high nicotine dependence should be given particular attention.

Effects of LiF on the properties of (Ba, Ca)(Ti, Sn, Hf)O3‐based multilayer ceramics co‐fired with Ni at reduced atmosphere

AbstractIn this work, (Ba0.97Ca0.03)(Ti0.96Sn0.005Hf0.035)O3–0.03MnCO3–xLiF (BCTSH–0.03M–xL, x = 0–6 mol%) multilayer piezoelectric ceramics were prepared by the solid‐state synthesis technique. The microstructure and piezoelectric properties of the samples sintered at the reduced atmosphere and co‐fired with the Ni base metal inner electrode were studied. The results showed that 3 mol% LiF could effectively reduce the sintering temperature from 1350 to 1200°C. BCTSH–0.03M–3L ceramics exhibited excellent electrical properties with d33 = 277 pC/N, d31 = −132 pC/N, kp = 0.350, Qm = 315, and εr = 3387. Furthermore, the complex impedance spectroscopy (e.g., activation energy) was used to analyze the doping mechanism of these obtained ceramics sintered at reduced atmosphere. The results indicated when LiF was added in a small amount (x ≤ 3), the bulk density was enhanced, and thus, the activation energy was also increased. Moreorver, when x &gt; 3, Li ions could partly enter the interstitial site of crystal structure resulting in the increase of activation energy. Rayleigh behaviors of reversible and irreversible domain wall contributions were analyzed. It was observed when x = 3, there was a larger Rayleigh coefficient, suggesting that this sample had the weaker pinning effect, and thus contributing to the higher d33 value due to the irreversible domain wall contribution. As x &gt; 3, the Rayleigh coefficient was found to decrease with increasing x due to the formation of the second phase, which could inhibit the motion of extrinsic domain wall. Finally, five‐layer multilayer piezoelectric ceramics co‐fired with inner Ni electrode were fabricated, and the electrical properties of five‐layer multilayer piezoelectric ceramics were found to be d33 = 1468 pC/N, d33* = 2000 (at 20 kV/cm), and kp = 0.342. To the best of our knowledge, the (Ba, Ca)(Ti, Sn, Hf)O3‐based lead‐free multilayer piezoelectric ceramics co‐fired with Ni‐based metal was first reported by us and used as the alternative multilayer ceramics for piezoelectric device applications.

Structural and biophysical properties of FopA, a major outer membrane protein of Francisella tularensis.

Francisella tularensis is an extremely infectious pathogen and a category A bioterrorism agent. It causes the highly contagious zoonosis, Tularemia. Currently, FDA approved vaccines against tularemia are unavailable. F. tularensis outer membrane protein A (FopA) is a well-studied virulence determinant and protective antigen against tularemia. It is a major outer membrane protein (Omp) of F. tularensis. However, FopA-based therapeutic intervention is hindered due to lack of complete structural information for membrane localized mature FopA. In our study, we established recombinant expression, monodisperse purification, crystallization and X-ray diffraction (~6.5 Å) of membrane localized mature FopA. Further, we performed bioinformatics and biophysical experiments to unveil its structural organization in the outer membrane. FopA consists of 393 amino acids and has less than 40% sequence identity to known bacterial Omps. Using comprehensive sequence alignments and structure predictions together with existing partial structural information, we propose a two-domain organization for FopA. Circular dichroism spectroscopy and heat modifiability assay confirmed FopA has a β-barrel domain consistent with alphafold2’s prediction of an eight stranded β-barrel at the N-terminus. Small angle X-ray scattering (SAXS) and native-polyacrylamide gel electrophoresis revealed FopA purified in detergent micelles is predominantly dimeric. Molecular density derived from SAXS at 31 Å shows putative dimeric N-terminal β-barrels surrounded by detergent corona and connected to C-terminal domains via flexible linker. Disorder analysis predicts N- and C-terminal domains are interspersed by a long intrinsically disordered region and alphafold2 predicts this region to be largely unstructured. Taken together, we propose a dimeric, two-domain organization of FopA in the outer membrane: the N-terminal β-barrel is membrane embedded, provides dimerization interface and tethers to membrane extrinsic C-terminal domain via long flexible linker. Structure determination of membrane localized mature FopA is essential to understand its role in pathogenesis and develop anti-tularemia therapeutics. Our results pave the way towards it.

Residual stress and domain switching in freeze cast porous barium titanate

Links between residual stress and domain switching in porous barium titanate ceramics were investigated using synchrotron X-ray diffraction as a function of an applied electric field. Barium titanate with highly aligned pores (with pore fraction vp = 0.52) was manufactured by freeze casting and compared with barium titanate produced via conventional pressing and sintering (with vp = 0.06). The domain switching fraction in the freeze cast ceramic was approximately double that of the low porosity barium titanate at a field of 3 kV/mm, attributed to a reduction in the residual stress from 70 MPa to 40 MPa with increased pore fraction. Whilst extrinsic domain switching was enhanced, the intrinsic lattice strain contribution to the piezoelectric properties was slightly reduced in the freeze cast barium titanate compared to the conventionally processed ceramic. These results point towards novel methods for engineering the functional properties of piezoelectric ceramics in the future.

Emotional Intelligence of Mid-Level Service Manager on Career Success: An Exploratory Study

Career success has been visualized as an outcome of multifaceted variables that operate both intrinsic and extrinsic domain of organizational ecosystem. Emotional intelligence is the state of mind how a person behaves rationally and logically in variety of emotional setup. The impact of emotional intelligence varies with profile and level of jobs. The study shows that the higher EI is highly related to greater accomplishment of jobs as we proceed to superior job responsibility. In the organizational hierarchy, the mid-level professionals are in between and focal layer of both the top-down and bottom-up approach. The rapid changes of roles as a mediating agent between top management, lower management and at the same time to play the role of transforming agent of the instructions from higher-ups to the lower ends are the testimony of high emotional intelligence behavioural components. The paper has attempted to unearth how the emotional intelligence are related to the career success particularly for the mid-level executives in the north-eastern region. This paper is empirical in nature based on primary as well as secondary information. The study result reflects that emotional intelligence has significant impact on achieving subjective career success among the respondents in the study region. However, the intensity of the impact (R2 value) may vary with the changing prospective of organizational climate and other temporal factors.

Research progress of the investigation of intrinsic and extrinsic origin of piezoelectric materials by X-ray diffraction

Ferroelectric/piezoelectric perovskites are an important class of functional material and have broad application prospects in commercial, industrial, military and other areas because of their high dielectric constants, high piezoelectric coefficients, and high electromechanical coupling coefficients. Their structures, applications, and physical mechanisms have been intensively studied in condensed matter physics and material science. The piezoelectric properties of ferroelectric materials mainly originate from the intrinsic field-induced lattice distortion and extrinsic domain inversion and domain wall motion. Therefore, the understanding of and the distinguishing between these mechanisms are important for ascertaining the origin of the high-piezoelectric properties and developing new functional materials. In this article, we review the research progress of technical means and methodology of analyzing the changes of crystal lattices and magnetic domains of materials under the action of an externally applied electric field through the high-energy synchrotron X-ray diffraction experiments. The techniques and analysis methods involved in the review cover the time-resolved X-ray diffraction, single/double-peak analysis, full-pattern refinement, center-of-mass calculation, and field-induced phase transformation analysis, which are used to study the intrinsic and extrinsic contributions to sample’s macroscopic properties. It is expected to provide the research methods, which fulfill the individual experimental requirements, and the technical support for the mechanism analysis of various piezoelectric materials through the introduction and review of various methods.

In-situ XRD study of actuation mechanisms in BiFeO3-K0.5Bi0.5TiO3-PbTiO3 ceramics

In the present study, we report a nonergodic relaxor ferroelectric composition for high temperature piezoelectric applications, 0.57BiFeO3-0.21K0.5Bi0.5TiO3-0.22PbTiO3, which exhibits Tm around 420 °C. By combining the results of in-situ synchrotron XRD and strain measurements using digital image correlation, a pseudocubic nonergodic relaxor to rhombohedral ferroelectric transformation is identified, accompanied by a volume strain close to zero. A methodology is developed to determine the crystallographic parameters of the transformed rhombohedral ferroelectric phase in a strain-free state, using the invariant intersection for diffraction stress analysis. The phase transformation process was analyzed by methods combining peak profile fitting and full pattern refinement; the results obtained illustrate the strain arising from the phase transformation, together with intrinsic/extrinsic contributions and anisotropy in the field-induced strain. The study reveals unusual microscopic strain behavior, distinguished from that of normal rhombohedral ferroelectrics, showing the combined properties of ergodic and normal ferroelectric materials and leading to a dominant intrinsic lattice strain together with a weaker extrinsic domain switching effect. The elastic coupling between different grain families is also reflected in their similar strain orientation distribution (SOD) functions.

Electric field-induced strain in core-shell structured BiFeO3[sbnd]K0.5Bi0.5TiO3[sbnd]PbTiO3 ceramics

A coherent core-shell structure in 0.24BiFeO3-0.56K0.5Bi0.5TiO3-0.20PbTiO3 ceramics, with Tm around 385 °C, was revealed using a combination of characterisation methods including scanning and transmission electron microscopy. The core regions consist of a cubic matrix with minor monoclinic phase with limited coherence length, while the shell regions are a tetragonal phase with characteristic long-range ordered ferroelectric domain structures. The electric field-induced strains for both core and shell regions were investigated by conducting an in-situ poling study using high energy synchrotron X-ray diffraction (XRD). A methodology is developed to evaluate both intrinsic (lattice strain) and extrinsic (domain switching) contributions for each phase based on diffraction peak profile fitting for multiple reflections.It is shown that there were no significant variations in the cubic and tetragonal phase fractions under an electric field in the range from −6 to +6 kV mm−1. An irreversible strain ∼0.04% was attributed mainly to ferroelectric domain switching in the tetragonal shell regions, while a reversible lattice strain ∼0.12% was identified in the pseudo-cubic core, leading to significant levels of intra-granular stress. Strain anisotropy, dependent on the crystallographic orientation of different grain families, was also evident. Macroscopic strain measurements, conducted using a novel digital image correlation (DIC) method, demonstrated the formation of typical ‘butterfly’-type strain-electric field loops and were consistent with the total strain values calculated from the XRD results.

Anomalously large lattice strain contributions from rhombohedral phases in BiFeO3-based high-temperature piezoceramics estimated by means of in-situ synchrotron x-ray diffraction

Thermally-stable (0.75-x)BiFeO3-0.25PbTiO3-xBa(Zr0.25Ti0.75)O3 (0.1 ≤ x ≤ 0.27) piezoelectric ceramics were reported to have excellent dielectric and electromechanical properties of d33∼405 pC/N, kp∼46%, ε33T/ε0∼1810, tanδ∼3.1% and Tc∼421 °C close to tetragonal (T)-rhombohedral (R) morphotropic phase boundary. The dielectric measurement indicates that R ferroelectric phase is gradually transformed into relaxor ferroelectric across the phase boundary due to the substitution of BZT for BF. The transmission electron microscopy and convergent beam electron diffraction provide clear evidences that both the R-T phase coexistence and polar nanodomains contribute to enhanced piezoelectric properties at x = 0.19 through cooperatively facilitating polarization orientation. In combination with the macroscopic piezoelectric coefficient measurement, the quantitative analysis of synchrotron diffraction data under electric fields suggests that extremely large lattice strain contribution predominantly from R phases plus little extrinsic domain switching contribution should dominate the piezoelectric response of the x = 0.19 sample, mainly owing to both irreversible field-induced T to R phase transition and irreversible non-180° domain switching.

Stress-dependent crystal structure of lanthanum strontium cobalt ferrite by in situ synchrotron X-ray diffraction

Lanthanum strontium cobalt ferrite La1-xSrxCo1-yFeyO3-δ (LSCF) is one of the most studied mixed ionic-electronic conductor materials due to electrical and transport properties, which are attractive for intermediate temperature solid oxide fuel cells (SOFCs), oxygen permeation membranes, and catalysis. The integration of such materials, however, depends on the thermal as well as mechanical behavior. LSCF exhibits nonlinear hysteresis during compressive stress-strain measurements, marked by a remanent strain and coercive stress, i.e., ferroelasticity. However, the origin of ferroelastic behavior has not been investigated under high compressive stress. This study, therefore, investigates the microscopic origin of stress-induced mechanical behavior in polycrystalline (La0.6Sr0.4)0.95Co0.2Fe0.8O3-δ using in situ synchrotron x-ray diffraction. The data presented here reveals that the strain response originates from the intrinsic lattice strain as well as the extrinsic domain switching strain without any apparent change in crystallographic symmetry. A comparison of the calculated microscopic strain contribution with that of a macroscopic measurement indicates a significant change in the relative contributions of intrinsic and extrinsic strain depending on the applied stress state, i.e., under maximum stress and after unloading. Direct evidence of the microscopic origin of stress-strain response outlined in this paper may assist in guiding materials design with the improved mechanical reliability of SOFCs.

Critical Role of Monoclinic Polarization Rotation in High-Performance Perovskite Piezoelectric Materials.

High-performance piezoelectric materials constantly attract interest for both technological applications and fundamental research. The understanding of the origin of the high-performance piezoelectric property remains a challenge mainly due to the lack of direct experimental evidence. We perform insitu high-energy x-ray diffraction combined with 2D geometry scattering technology to reveal the underlying mechanism for the perovskite-type lead-based high-performance piezoelectric materials. The direct structural evidence reveals that the electric-field-driven continuous polarization rotation within the monoclinic plane plays a critical role to achieve the giant piezoelectric response. An intrinsic relationship between the crystal structure and piezoelectric performance in perovskite ferroelectrics has been established: A strong tendency of electric-field-driven polarization rotation generates peak piezoelectric performance and vice versa. Furthermore, the monoclinic M_{A} structure is the key feature to superior piezoelectric properties as compared to other structures such as monoclinic M_{B}, rhombohedral, and tetragonal. A high piezoelectric response originates from intrinsic lattice strain, but little from extrinsic domain switching. The present results will facilitate designing high-performance perovskite piezoelectric materials by enhancing the intrinsic lattice contribution with easy and continuous polarization rotation.

Lateral Magnetically Modulated Multilayers by Combining Ion Implantation and Lithography.

The combination of lithography and ion implantation is demonstrated to be a suitable method to prepare lateral multilayers. A laterally, compositionally, and magnetically modulated microscale pattern consisting of alternating Co (1.6 µm wide) and Co-CoO (2.4 µm wide) lines has been obtained by oxygen ion implantation into a lithographically masked Au-sandwiched Co thin film. Magnetoresistance along the lines (i.e., current and applied magnetic field are parallel to the lines) reveals an effective positive giant magnetoresistance (GMR) behavior at room temperature. Conversely, anisotropic magnetoresistance and GMR contributions are distinguished at low temperature (i.e., 10 K) since the O-implanted areas become exchange coupled. This planar GMR is principally ascribed to the spatial modulation of coercivity in a spring-magnet-type configuration, which results in 180° Néel extrinsic domain walls at the Co/Co-CoO interfaces. The versatility, in terms of pattern size, morphology, and composition adjustment, of this method offers a unique route to fabricate planar systems for, among others, spintronic research and applications.

Fe-Mg interdiffusion in orthopyroxene

We have measured Fe-Mg interdiffusion coefficients, D Fe-Mg , parallel to the three main crystallographic axes in two natural orthopyroxene single crystals [approximately En 98 Fs 1 ( X Fs = X Fe = 0.01) and En 91 Fs 9 ] using diffusion couples consisting of a 20–90 nm thick silicate thin film deposited under vacuum on polished and oriented pyroxene single crystals. The thin films were prepared using pulsed laser ablation of polycrystalline olivine pellets (composition: Fo 30 Fa 70 ). Samples were annealed for 4–337 h at 870–1100 °C under atmospheric pressure in a continuous flow of CO + CO 2 to control the oxygen fugacity, f O 2 , between 10 −11 and 10 −7 Pa within the stability field of pyroxene. Film thickness and compositional profiles were measured using Rutherford backscattering spectroscopy (RBS) on reference and annealed samples, and Fe concentration depth profiles were extracted from the RBS spectra and fitted numerically considering a compositional dependence of D Fe-Mg in orthopyroxene. We obtain an Arrhenius relationship for both types of crystals, but only for the more Fe-rich composition a dependence on f O 2 could be clearly identified. For diffusion along [001] in the composition Fs 9 , least-squares regression of the log D Fe-Mg vs. reciprocal temperature yields the following Arrhenius equation: D Fe - Mg [ m 2 / s ] = 1 . 12 × 10 − 6 ( f o 2 [ Pa ] ) 0 . 053 ± 0 . 027 exp [ – 308 ± 23 [ kJ / mol ] / ( R T ) ] . D Fe-Mg in Opx with X Fe = 0.01 obeys a relationship that does not depend on f O 2 : D Fe - Mg [ m 2 / s ] = 1 . 66 × 10 − 4 exp [ – 377 ± 30 [ kJ / mol ] / ( R T ) ] . Diffusion along [001] is faster than diffusion along [100] by a factor of 3.5, while diffusion along [010] is similar to that along [001]. Comparison of D Fe-Mg and rates of order-disorder kinetics indicates that for f O 2 around the IW buffer and lower, diffusion in natural orthopyroxene becomes insensitive to f O 2 , which could be related to a transition in the diffusion mechanism from a transition metal extrinsic (TaMED) domain to a pure extrinsic (PED) domain. This behavior is analogous to that observed for Fe-Mg diffusion in olivine and this complexity precludes the formulation of a closed form expression for the composition and f O 2 dependence of D Fe-Mg in orthopyroxene at present. We were not able to quantitatively constrain the dependence of D Fe-Mg on the X Fs content from the profile shapes, but consideration of the experimentally measured diffusion coefficients along with the data for order-disorder kinetics suggests that the compositional dependence is weaker than previously estimated, at least for orthopyroxene with X Fe T and f O 2 range of available experimental data, Fe-Mg interdiffusion in orthopyroxene is slower than in olivine and aluminous spinel, comparable to garnet, and faster than in clinopyroxene.