Interfacial Moments Research Articles

Development of a novel crack-resistance technique for concrete slab in the hogging moment region of continuous composite beam

Composite steel-concrete beams offer distinct mechanical advantages. However, concrete cracking in the hogging moment region limits the composite performance of the material. This study presents an innovative technique for enhancing the crack resistance of continuous steel-concrete composite beams, which involves the prestressing of the concrete slab in the hogging moment region through post-tensioning. Following the completion of the concrete slab in the sagging moment region, the prestress is released, thereby preserving pre-compression stress in the hogging moment region without the need for long-term prestressing. This technique is enhanced using uplift-restricted and slip-free connectors, which improve the efficiency of pre-stress introduction. Experimental tests were conducted on composite beams employing this novel technique, alongside numerical simulations. The results indicated that the proposed technique significantly mitigated concrete cracking in the hogging moment region. Specifically, the cracking load of the specimen using the new technique increased by 467 % compared to the traditional composite beam specimen, accompanied by a substantial reduction in both the quantity and width of cracks. Other primary mechanical performance indicators remained relatively similar; however, the new technique exhibited a 14 % increase in the ductility coefficient compared with the traditional method. Additionally, this technique influenced interface slip, moment redistribution, and strain response along the cross-section in both the hogging and sagging moment regions. The numerical results aligned closely with the experimental data, confirming their accuracy and effectiveness. The simulations provided solutions for various construction stages by incorporating different connection constitutive models with adequate precision. A parametric analysis was conducted, revealing a design method for the innovative technique.

Impact of orbital hybridization on spin-polarized electronic transport through Ni-MAPbI3 interfaces

The solution-processed methylammonium lead tri-iodine (MAPbI3), with long spin lifetimes and large spin diffusion lengths, has merit for developing stable perovskite spin valves (PeSV) with low saturation fields. By far, it remains challenging to avoid ill-defined ferromagnet-MAPbI3 interfaces during device fabrications using solution methods and to quantify the hybridized interfacial electronic and magnetic structures. Herein, an annealing-free method was developed for the fabrication of MAPbI3 based PeSV. In comparison to a thermally annealed device, an improved room temperature magnetoresistance (MR) was achieved. We found remarkable interfacial contributions to anisotropic magnetoresistance and MR. The first-principles calculation was further adopted to quantify the interfacial spin and orbital moments. Our results suggest that the orbital hybridization and the spin transfer are remarkable for the formation of the spin-dependent interfacial density of states. It consequently affects magnetic switching behaviors. This study holds an exceptionally important role for a deep understanding of the spin-polarized electronic transport through the Ni-MAPbI3 hybridized interface.

Embedded Insurance/Microinsurance in Financial Services: Key to Financial Inclusion

Financial inclusion is a goal vigorously followed by all governments the world over. Nowadays, due to technological progress, the interplay of technology with the provision of financial services is increasingly becoming quite common and yielding the desired results. The Indian technology landscape has moved fast facilitated by a huge amount of public investment. The ‘Unified Payments Interface (UPI) moment’ has become a cliché in financial circles. From the UPI moment in payments, we are now experiencing high growth in lending and insurance. Partnerships between legacy insurers and InsurTech and e-commerce platforms/networks are leading to new competencies and new, innovative insurance products. The study suggests that embedded, personalised and customised insurance products must be experimented with and introduced in government marketplaces which attract many small buyers and suppliers.

Direct observation of antiferromagnetic domains and field-induced reversal in Pt/Cr2O3/Pt epitaxial trilayers

Antiferromagnet does not show the net magnetization, whereas the finite uncompensated moment can residue at the surface. On the surface of the magnetoelectric antiferromagnet, the finite boundary magnetization can acquire the magnetic response. In this paper, we address the magnetic response of the boundary magnetization in the Pt/magnetoelectric Cr2O3/Pt epitaxial trilayer based on the anomalous Hall effect (AHE) and the soft x-ray magnetic circular dichroism (XMCD). Decreasing the Cr2O3 thickness down to 15 nm, the film acquired the magnetic responsiveness, which manifested as the rectangular hysteresis in the magnetic field dependence of the AHE. The sizable XMCD intensity and the rectangular magnetic field dependence of the XMCD intensity revealed that the magnetic response was attributed to the interfacial Cr moment. The detailed investigation of AHE and XMCD revealed that the domain wall motion dominated the reversal process of the boundary magnetization, which was directly visualized by the scanning XMCD microscope.

Extension–bending coupling phenomena and residual hygrothermal stresses effects on the Energy Release Rate and mode mixity of generally layered laminates

This article presents a novel analytical solution to the delamination problem of interface deformable generally layered (asymmetric and unbalanced) composite laminates. The governing equation describing the interface forces and moments is obtained for the reduced form of the first-order shear deformation theory of plates (FSDT) under plane strain assumptions and accounts for the extension–bending coupling phenomena and residual hygrothermal stresses, both of which have been neglected in the past. The interface forces and moments are included in a novel generalization of the J-integral which is used for the estimation of the Energy Release Rate (ERR). The analytical results of the ERR and the mode mixity exhibit a great agreement with the results of Finite Element (FE) models developed using the Cohesive Zone Method (CZM) and the Virtual Crack Closure Technique (VCCT) for a Double Cantilever Beam (DCB) test of a generally layered fibre metal laminate.

Considerations about the gas fraction in two-phase electrochemical reactors by using a rigorous hydrodynamic model

The experimental evidence that a limiting value of gas fraction is achieved in a gas-liquid dispersion as the gas volumetric flow rate is increased is explained by means of a rigorous hydrodynamic model. The mathematical treatment, based on the Eulerian concept applied to each phase, considers a population balance with a range of bubble sizes allowing the coalescence and breakup between them; and it is implemented in the OpenFOAM framework. It is concluded that the limiting gas fraction is a consequence of the increase of the gas velocity and the constancy of the drag term of the interfacial exchange moment as the volumetric gas flow is enlarged. A simplified hydrodynamic model is also reported that closely matches both the rigorous one and the experimental results under limiting operating conditions.

Multi-physical modeling and fabrication of high-performance IPMC actuators with serrated interface

Ionic Polymer–Metal Composite (IPMC) has been widely recognized as a promising and representative candidate of soft intelligent materials actuated under low voltage. In the last few years, the importance of the electrode/substrate interface has received growing attention for research on both the modeling of ion-based mass transport and practical performance of the manipulation of ionic electro-active actuators. In this paper, based on a macroscopic serrated interface morphology, the influences of the interface were revealed comprehensively by distinguishing the bending direction as well as the variation of interfacial area, excisional volume and moment of inertia. The offsetting interaction from different aspects were analyzed in detail. On this basis, an interesting result showed that, contrary to current understanding, an enlarged interface area did not necessarily lead to better deformation, which was primarily ascribed to the trade-off of influences from the increasing excisional volume and decreasing bending inertia moment. In addition, a corresponding fabrication process was established, which verified experimentally that IPMC with a super simple macroscopic serrated interface can present a high electro-active performance, providing a minimalist design strategy for ionic electroactive polymer structures.

Experimental and theoretical study of field-dependent spin splitting at ferromagnetic insulator-superconductor interfaces.

We present a combined experimental and theoretical work that investigates the magnetic proximity effect at a ferromagnetic insulator–superconductor (FI–S) interface. The calculations are based on the boundary condition for diffusive quasiclassical Green’s functions, which accounts for arbitrarily strong spin-dependent effects and spin mixing angles. The resulting phase diagram shows a transition from a first-order to a second-order phase transition for large spin mixing angles. The experimentally found differential conductance of an EuS-Al heterostructure is compared with the theoretical calculation. With the assumption of a uniform spin mixing angle that depends on the externally applied field, we find good agreement between theory and experiment. The theory depends only on very few parameters, mostly specified by the experimental setup. We determine the effective spin of the interface moments as J ≈ 0.74ℏ.

Interfacial peeling loads in the TBC with an air hole: Analytical solutions and viscoplasticity modelling

This work evaluates the temperature field, stresses, and peeling loads in thermal barrier coatings (TBCs) with air holes subjected to cyclic thermo-mechanical loads during a complete flight. Analytical formulae for the steady-state temperature field and interfacial peeling loads are developed considering thermal gradients in the thickness and longitudinal directions. In addition, viscoplasticity finite element modelling is conducted for the mechanical behaviors of the TBC system. A unified Chaboche-Lemaitre constitutive model that combines a power flow rule with non-linear anisothermal evolution of isotropic and kinematic hardening is integrated into the numerical framework. The results show tensile peeling stress and shear stress are generated in the vicinity of the hole, which motivates the initiation and propagation of hole-edge cracks. The maximum peeling and shear stresses locate close to the thermally grown oxide/bond coat interface and they increase with increasing hole radius. The interfacial peeling moment and shear force could characterize edge cracking in TBCs. As the hole radius increases, the interfacial peeling moment and shear force increase quickly when the hole radius is less than 1 mm but remain stable when the hole radius is beyond 2 mm. This work not only helps to explain the failure mechanisms of hole-edge delamination and spallation in TBCs but also guides the design of thermal barrier coated hot-section components in gas turbines.

First Principles Investigation on Electrically Controlled Magnetic Moments of Ultrathin Palladium Film on MgO(001)

Electric field dependence of magnetic, electronic, and structural properties in a Pd bilayer film on MgO (001) is investigated by using the first-principles electronic structure calculations within density functional theory. We find that, due to the lattice mismatch of 6.7 %, a ferromagnetic ground state is stabilized at zero electric field on an otherwise paramagnetic Pd with the spin magnetic moments of m = 0.31 and 0.34 μB in surface and interface Pd, respectively. The application of an external electric field, E, causes the Pd magnetic moments to be modulated in a site- and electric field-dependent manner. As the external electric field pointing inward to the Pd surface is increased up to the critical value of 1.3 V/Å, the surface Pd moment is barely changed while the interfacial Pd moment increases linearly with E. Above this critical electric field, the moments of both the interfacial and surface Pd atoms exhibit nonlinear increase with E and reach up to 0.34 (surface) and 0.41 (interface) μB at E = 2.5 V/Å. When the electric field direction is inverted, a similar dependence on E is obtained for both Pd atoms at the critical electric field value of -0.5 V/Å. The peculiar behavior of the induced magnetic moments is explained by combining the linearized Stoner and itinerant conduction models. We reveal that this prominent magnetoelectric effect is due to the modulated charge occupancy of Pd 4d-states in the minority spin channel in which the dSUBzSUP2/SUP/SUB and dSUBxSUP2/SUP-ySUP2/SUP/SUB orbitals play crucial roles.

Perpendicular magnetic anisotropy induced by NiMn-based antiferromagnetic films with in-plane spin orientations: Roles of interfacial and volume antiferromagnetic moments

Antiferromagnetic (AFM) thin films are promising materials for engineering the magnetic anisotropy of adjacent ferromagnetic (FM) films. In this work, we explored the effects of triggering perpendicular magnetic anisotropy (PMA) of FM films by applying a series of NiMn-based AFM films with in-plane-oriented spin structures. The vertically expanded face-centered tetragonal ${\mathrm{Ni}}_{50}{\mathrm{Mn}}_{50}$ films alone could not induce PMA in Co/Ni films. By contrast, PMA was triggered through the application of Mn-rich NiMn alloy films or ${\mathrm{Ni}}_{50}{\mathrm{Mn}}_{50}/1$-monolayer Mn $(\mathrm{Mn}/1\text{\ensuremath{-}}\mathrm{ML} {\mathrm{Ni}}_{50}{\mathrm{Mn}}_{50})$ heterostructures. Detailed analyses of a series of samples indicated that two criteria must be met for a NiMn-based AFM film to trigger PMA in a neighboring FM film: (1) perpendicular interface crystalline anisotropy of interfacial uncompensated Mn moments must be established, and (2) strengthened lateral exchange coupling to volume AFM moments must be made. This paper clarifies how NiMn-based AFM films with in-plane-oriented AFM spin structures trigger the PMA of FM films, thus identifying a pathway to increase control over antiferromagnet-induced PMA through the interface/volume magnetic engineering of AFM layers.

Intra-unitcell cluster-cluster magnetic compensation and large exchange bias in cubic alloys

Composite quantum materials are the ideal examples of multifunctional systems, which simultaneously host more than one novel quantum phenomenon in physics. Here, we present a combined theoretical and experimental study to demonstrate the presence of an extremely large exchange bias in the range 0.8--2.7 T and a fully compensated magnetic state (FCF) in a special type of Pt and Ni-doped ${\mathrm{Mn}}_{3}\mathrm{In}$ cubic alloy. Here, oppositely aligned uncompensated moments in two different atomic clusters sum up to zero, which are responsible for the FCF state. Our density functional theory (DFT) calculations show the existence of several possible ferrimagnetic configurations with the FCF as the energetically most stable one. The microscopic origin of the large exchange bias can be interpreted in terms of the exchange interaction between the FCF background and the uncompensated ferrimagnetic clusters stabilized due to its negligible energy difference with respect to the FCF phase. We utilize pulsed magnetic field up to 60 T and 30 T static-field magnetization measurements to confirm the intrinsic nature of exchange bias in our system. Finally, our Hall effect measurements demonstrate the importance of uncompensated noncoplanar interfacial moments for the realization of large EB. The present finding of gigantic exchange bias in a unique compensated ferrimagnetic system opens up a direction for the design of novel quantum phenomena for the technological applications.

Lamellar magnetism and exchange bias in billion-year-old metamorphic titanohematite with nanoscale ilmenite exsolution lamellae – III. Atomic-magnetic basis for experimental results

SUMMARY Lamellar magnetism is a source of remanent magnetization in natural rocks different from common bulk magnetic moments in ferrimagnetic minerals. It has been found to be a source for a wide class of magnetic anomalies with extremely high Koenigsberger ratio. Its physical origin are uncompensated interface moments in contact layers of nanoscale ilmenite lamellae inside an hematite host, which also generate unusual low-temperature (low-T) magnetic properties, such as shifted low-T hysteresis loops due to exchange bias. The atomic-magnetic basis for the exchange bias discovered in the hematite-ilmenite system is explored in a series of papers. In this third article of the series, simple models are developed for lamellae interactions of different structures when samples are either cooled in zero-field, or field-cooled in 5 T to temperatures below the ordering temperature of ilmenite. These models are built on the low-temperature measurements described earlier in Paper II. The important observations include: (i) the effects of lamellar shapes on magnetic coupling, (ii) the high-T acquisition of lamellar magnetism and low-T acquisition of magnetization of ilmenite lamellae, (iii) the intensity of lamellar magnetism and the consequent ilmenite magnetism in populations of randomly oriented crystals, (iv) lattice-preferred orientation of the titanohematite host crystal populations and (v) the effects of magnetic domain walls in the host on hysteresis properties. Based on exemplary growth models of lamellae with different geometries and surface couplings we here provide simple models to assess and explain the different observations listed above. Already the simplified models show that the shapes of the edges of ilmenite lamellae against their hematite hosts can control the degree of low-T coupling between ilmenite, and the lamellar magnetic moments. The models also explain certain features of the low-T exchange bias in the natural samples and emphasize the role of lattice-preferred orientation upon the intensity of remanent magnetization. The inverse link between ilmenite remanence and exchange-bias shift in bimodal low-T ilmenite lamellae is related to different densities of hematite domain walls induced by the clusters of ilmenite lamellae.

Nondestructive detection of the interfacial failure of steel-polymer sandwich composites during forming process

Steel-polymer composites have low density, high specific flexural stiffness and vibration damping properties over other metal materials. However, the weak interfaces between steel and polymer sheet are the typical locations where the failure occurs. Furthermore, interfacial failure is a fatal reason of the degradation of mechanical properties. Therefore, predicting interfacial failure of the final product is an important technology in commercialization of steel-polymer composites. In this study, we built forming limit diagram (FLD) based on two different failure modes: failure of the bottom skin steel and interfacial failure between the skin steel and core polymer. Acoustic emission (AE) technique was conducted to observe the interfacial failure moment. Peak frequency was found to be the key feature to distinguish interfacial failure. Peak frequency band that indicates interfacial failure was from 300 kHz to 500 kHz. This peak frequency band made it possible to build FLD considering the interfacial failure.

Manipulatable Interface Electric Field and Charge Transfer in a 2D/2D Heterojunction Photocatalyst via Oxygen Intercalation

Charge separation is the most important factor in determining the photocatalytic activity of a 2D/2D heterostructure. Despite the exclusive advantages of 2D/2D heterostructure semiconductor systems such as large surface/volume ratios, their use in photocatalysis is limited due to the low efficiency of charge separation and high recombination rates. As a remedy for the weak interlayer binding and low carrier transport efficiency in 2D/2D heterojunctioned semiconductors, we suggested an impurity intercalation method for the 2D/2D interface. PtS2/C3N4, as a prototype heterojunction material, was employed to investigate the effect of anion intercalation on the charge separation efficiency in a 2D/2D system using density functional theory. With oxygen intercalation at the PtS2/C3N4 interface, a reversed and stronger localized dipole moment and a built-in electric field were induced in the vertical direction of the PtS2/C3N4 interface. This theoretical work suggests that the anion intercalation method can be a way to control built-in electric fields and charge separation in designs of 2D/2D heterostructures that have high photocatalytic activity.

Emergence of Multispinterface and Antiferromagnetic Molecular Exchange Bias via Molecular Stacking on a Ferromagnetic Film

AbstractHeterointerfaces may exhibit unexpected physical properties distinct from intrinsic properties of component materials. In particular, metal–organic interfaces can drive unique interfacial spin moments, which are often called molecular spinterface. Here, van der Waals stacking of molecular layers may lead to variations in the intra/interlayer exchange coupling resulting in multiple ground states, which is highly desired for multifunctional magnetic devices. In this report, the emergence of molecular multispinterface of paramagnetic cobalt‐octaethyl‐porphyrin (CoOEP) layers in a Fe/CoOEP heterostructure is demonstrated through the interfacial layer and a successive antiferromagnetic molecular spin chain. The disentangled interfacial ferromagnetic spins lead to multiple magnetic ground states and behave as additional spin‐dependent scattering centers, as evidenced through the magnetotransport study. In addition, the antiferromagnetic molecule spin chain derives tunable exchange bias, which signifies the dominance of the antiferromagnetic interfacial interaction. Theoretical calculations demonstrate spin configurations of the molecular chain and the antiferromagnetic interfacial coupling through oxygen intermediaries. The development of the molecular multispinterface and controllable exchange bias therein will provide a promising route for the active control of multivalued data processing at the nanoscale.

Longitudinal spin Seebeck effect in pyrochlore iridates with bulk and interfacial Dzyaloshinskii-Moriya interaction

The longitudinal spin-Seebeck effect (SSE) in magnetic insulator$|$non-magnetic metal heterostructures has been theoretically studied primarily with the assumption of an isotropic interfacial exchange coupling. Here, we present a general theory of the SSE in the case of an antisymmetric Dzyaloshinskii-Moriya interaction (DMI) at the interface, in addition to the usual Heisenberg form. We numerically evaluate the dependence of the spin current on the temperature and bulk DMI using a pyrochlore iridate as a model insulator with all-in all-out (AIAO) ground state configuration. We also compare the results of different crystalline surfaces arising from different crystalline orientations and conclude that the relative angles between the interfacial moments and Dzyaloshinskii-Moriya vectors play a significant role in the spin transfer. Our work extends the theory of the SSE by including the anisotropic nature of the interfacial Dzyaloshinskii-Moriya exchange interaction in magnetic insulator$|$non-magnetic metal heterostructures and can suggest possible materials to optimize the interfacial spin transfer in spintronic devices.

Stress analysis of the thermal barrier coating system near a cooling hole considering the free-edge effect

Due to the thermal mismatch between layers and the free-edge effect, interfacial peeling and shear stresses are generated locally around the edges of cooling holes in a thermal barrier coating (TBC)–film cooling system. These interfacial peeling and shear stresses may lead to modes I and II edge delamination, resulting in TBC spallation around the cooling hole. In this study, analytical and numerical models were built to study the stress and interfacial cracking behaviors of TBCs near the cooling hole. Analytical solutions for interfacial peeling moment and shear force at each layer were obtained to analyze the free-edge effect on the stress distributions in TBCs, and they were verified by the finite element calculations. The results showed that interfacial peeling moment and shear force were functions of the hole radius and thicknesses of top coat and oxide layer. The increase of interfacial peeling moment and shear force raised the likelihood of edge cracking around the hole. Derived by the local stresses, the interfacial cracks in TBCs initiated and propagated from the hole edge upon cooling.

Interface moment dynamics and its contribution to spin-transfer torque switching process in magnetic tunnel junctions

A practical problem for memory applications involving perpendicularly magnetized magnetic tunnel junctions is the reliability of switching characteristics at high-bias voltage. Often it has been observed that at high-bias, additional error processes are present that cause a decrease in switching probability upon further increase of bias voltage. We identify the main cause of such error-rise process through examination of switching statistics as a function of bias voltage and applied field, and the junction switching dynamics in real time. These experiments show a coincidental onset of error-rise and the presence of a new low-frequency microwave emission well below that dictated by the anisotropy field. We show that in a few-macrospin coupled numerical model, this is consistent with an interface region with concentrated perpendicular anisotropy, and where the magnetic moment has limited exchange coupling to the rest of the layers. These results point to the important role high-frequency interface magnetic moment dynamics play in determining the switching characteristics of these tunnel junction devices.

Simulation of thermal stress in ion beam sputtered Ta2O5/SiO2 multilayer coatings on different substrates by finite element analysis

The delamination and failure of thin-film system induced by thermal stress have long been of interest in processes of coatings deposition. In spite of ion beam sputtering depositing (IBSD) exhibiting low processing temperature, the thermal stress still has significant influence when a tremendous difference exists between physical and thermal properties of the bonded materials. Therefore, the investigation for a conventional optical multilayer stack consisting of tantalum pentoxide and silicon dioxide deposited on four substrates with different materials (calcium fluoride, zinc selenide, silicon, and fused silica) in this paper is presented. In order to calculate the thermal stress distribution along thickness remote from the edge, a two-dimensional finite element model of the system is established. Based on this model, the peeling stress and the shear stress at the interfaces between the substrates and coatings are discussed to judge whether the interface delamination is possible, as well as the interfacial peeling moments and interfacial shear forces. Meanwhile, the corresponding samples were coated by the method of IBSD, and the experimental results show excellent agreement with the predictions. Based on the above analyses, we discussed the delamination phenomenon of the experiment, and also proposed some possible approaches to reduce the possibility of the interface delamination.