磁组装薄膜材料的结构及磁各向异性研究

在近平行方向磁场作用下,制备出有序平行线形阵列结构的纳米Fe3O4/氟碳树脂磁组装薄膜材料。利用偏光显微镜和紫外-可见-近红外分光光度计(UVPC)研究不同场强条件以及不同粉体含量对薄膜内部阵列结构的影响;采用振动样品磁强计(VSM)研究不同条件下磁组装薄膜的磁各向异性。结果表明:随着磁场强度增加,阵列变得越来越密集,随着Fe3O4含量的增加,线形阵列逐渐变粗;磁组装薄膜具有明显的磁各向异性,且随着磁场强度增加以及粉体的减少其等效磁各向异性常数逐渐增大。     

An Examination of Various Methods of Minimising Strain Gradients in 3D Embedded Strain Gauge Analysis

This paper is a review of different methods used to reduce the effect of strain gradients in experimental models with 3D embedded strain gauged transducers. A detailed analysis of various methods used in relation to research carried out on a prosthetic hip implant is investigated. The methods to reduce these gradient effects detail the importance of the selection of the most suitable 3D transducer pattern and establishing the locations on the model where strain gradients are least problematic. It is also shown that the use of large‐scale models helps minimise the effect a gradient may have on data. Another way of avoiding strain gradients is to use axisymmetric models and embed the gauges at the same radius in the model but at a different angular orientation from the central axis. The strain gradient across the 3D embedded strain gauge transducer can be reduced using the methods described here so that significant errors in the final tensor do not materialise.     

各向异性热压稀土永磁体的热变形机制及微磁结构研究

重点研究制备工艺对各向异性热压稀土永磁体性能的影响,探讨了热压永磁体的热变形机理和数学描述模型,并尝试从微磁结构的角度研究各向异性纳米晶Nd-Fe-B磁体,揭示纳米晶粒之间的静磁和交换耦合相互作用、磁化和反磁化、热退磁等微观机制。获得了最佳磁性能为:Hcj=1 157 kA/m,Br=1.465 T,(BH)max=426 kJ/m3纳米晶Nd-Fe-B磁体。     

Interlaminar Stress Determination in Carbon Fibre Epoxy Composites with the Embedded Strain Gauge Technique

Abstract: In order to determine interlaminar stresses, strain gauges have been embedded in carbon fibre/epoxy composites. Insulation problems occurring because of the electrical conductivity of the carbon fibres were successfully resolved with the help of special foils. Measurements on unidirectional and angle‐ply laminates were in good agreement with calculations based on the classical laminate theory. Moreover, the laminate strength was not significantly affected by the embedded strain gauges. The technique may also be applied to residual stress determination in composite components.     

Influence of Metalloid Elements on the Magnetic Properties and Anisotropy of FeNi-based Amorphous Alloys

The magnetic properties and anisotropy of amor-phous(Fe_(80)Ni_(20))_(78)Si_xB_(22-x).alloys have been investigatedsystematically.The maximum permeability,coercive forceand remanence have been determined for as-prepared andannealed samples,The results on the technical magneticproperties of this alloy system have been discussed andcompared with Masumoto's.     

The Reinforcement Effect of Strain Gauges Embedded in Low Modulus Materials

The reinforcement effect of electrical resistance strain gauges is well‐described in the literature, especially for strain gauges installed on surface. This paper considers the local reinforcement effect of strain gauges embedded within low Young modulus materials. In particular, by using a simple theoretical model, already used for strain gauges installed on the surface, it proposes a simple formula that allows the user to evaluate the local reinforcement effect of a generic strain gauge embedded on plastics, polymer composites, etc. The theoretical analysis has been integrated by numerical and experimental analyses, which confirmed the reliability of the proposed model.     

Dimerization Triggered Magnetoelectric Coupling Effect and Magnetic Anisotropy in Organic Ternary Crystals

Developing a new universal strategy to design all organic ferromagnets or multiferroics with satisfactory properties always remains challenging. In this work, ternary charge transfer crystals are fabricated to realize organic multiferroic magnetoelectric coupling effect. Through incorporating the third component into binary crystals, a dimerization between neighbor donor and acceptor is induced to form a lattice symmetry breaking, where a nonpolar to polar phase transition is ensuing to lead to a dipolar polarization. Magnetic field can effectively tune the dipolar polarization to present a magnetoelectric coupling effect. Moreover, the introduction of the third component can result in a rearrangement in molecular configuration to modify the electron–phonon interaction. As a result, anisotropic magnetism is observed due to anisotropic electron–phonon coupling in ternary crystals. Overall, this study forecasts that incorporating an appropriate third component is a potential method for designing all organic multiferroics.     

Giant Enhancements of Perpendicular Magnetic Anisotropy and Spin‐Orbit Torque by a MoS2 Layer

2D transition metal dichalcogenides have attracted much attention in the field of spintronics due to their rich spin‐dependent properties. The promise of highly compact and low‐energy‐consumption spin‐orbit torque (SOT) devices motivates the search for structures and materials that can satisfy the requirements of giant perpendicular magnetic anisotropy (PMA) and large SOT simultaneously in SOT‐based magnetic memory. Here, it is demonstrated that PMA and SOT in a heavy metal/transition metal ferromagnet structure, Pt/[Co/Ni]₂, can be greatly enhanced by introducing a molybdenum disulfide (MoS₂) underlayer. According to first‐principles calculation and X‐ray absorption spectroscopy (XAS), the enhancement of the PMA is ascribed to the modification of the orbital hybridization at the interface of Pt/Co due to MoS₂. The enhancement of SOT by the role played by MoS₂ is explained, which is strongly supported by the identical behavior of SOT and PMA as a function of Pt thickness. This work provides new possibilities to integrate 2D materials into promising spintronics devices.     

Ionic Liquid Gating Control of Spin Reorientation Transition and Switching of Perpendicular Magnetic Anisotropy

Electric field (E‐field) modulation of perpendicular magnetic anisotropy (PMA) switching, in an energy‐efficient manner, is of great potential to realize magnetoelectric (ME) memories and other ME devices. Voltage control of the spin‐reorientation transition (SRT) that allows the magnetic moment rotating between the out‐of‐plane and the in‐plane direction is thereby crucial. In this work, a remarkable magnetic anisotropy field change up to 1572 Oe is achieved under a small operation voltage of 4 V through ionic liquid (IL) gating control of SRT in Au/[DEME]⁺[TFSI]^?/Pt/(Co/Pt)₂/Ta capacitor heterostructures at room temperature, corresponding to a large ME coefficient of 378 Oe V^?1. As revealed by both ferromagnetic resonance measurements and magnetic domain evolution observation, the magnetization can be switched stably and reversibly between the out‐of‐plane and in‐plane directions via IL gating. The key mechanism, revealed by the first‐principles calculation, is that the IL gating process influences the interfacial spin–orbital coupling as well as net Rashba magnetic field between the Co and Pt layers, resulting in the modulation of the SRT and in‐plane/out‐of‐plane magnetization switching. This work demonstrates a unique IL‐gated PMA with large ME tunability and paves a way toward IL gating spintronic/electronic devices such as voltage tunable PMA memories.     

Temperature Peculiarities of Magnetic Anisotropy in (Ga,Mn)As: The Role of the Hole Concentration

It is demonstrated by SQUID measurements that (Ga,Mn)As films can exhibit perpendicular easy axis at low temperatures, even under compressive strain, provided that the hole concentration is sufficiently small. In such films, the easy axis assume a standard in-plane orientation when the temperature is increased towards the Curie temperature. The findings are shown to corroborate the predictions of the mean-field Zener model for strained (III,Mn)V ferromagnetic semiconductors.