Recent development in lead-free perovskite piezoelectric bulk materials

Multiferroic bismuth ferrite-based materials for multifunctional applications: Ceramic bulks, thin films and nanostructures

Building upon the success and relevance of the 2014 Magnetism Roadmap, this 2017 Magnetism Roadmap edition follows a similar general layout, even if its focus is naturally shifted, and a different group of experts and, thus, viewpoints are being collected and presented. More importantly, key developments have changed the research landscape in very relevant ways, so that a novel view onto some of the most crucial developments is warranted, and thus, this 2017 Magnetism Roadmap article is a timely endeavour. The change in landscape is hereby not exclusively scientific, but also reflects the magnetism related industrial application portfolio. Specifically, Hard Disk Drive technology, which still dominates digital storage and will continue to do so for many years, if not decades, has now limited its footprint in the scientific and research community, whereas significantly growing interest in magnetism and magnetic materials in relation to energy applications is noticeable, and other technological fields are emerging as well. Also, more and more work is occurring in which complex topologies of magnetically ordered states are being explored, hereby aiming at a technological utilization of the very theoretical concepts that were recognised by the 2016 Nobel Prize in Physics. Given this somewhat shifted scenario, it seemed appropriate to select topics for this Roadmap article that represent the three core pillars of magnetism, namely magnetic materials, magnetic phenomena and associated characterization techniques, as well as applications of magnetism. While many of the contributions in this Roadmap have clearly overlapping relevance in all three fields, their relative focus is mostly associated to one of the three pillars. In this way, the interconnecting roles of having suitable magnetic materials, understanding (and being able to characterize) the underlying physics of their behaviour and utilizing them for applications and devices is well illustrated, thus giving an accurate snapshot of the world of magnetism in 2017. The article consists of 14 sections, each written by an expert in the field and addressing a specific subject on two pages. Evidently, the depth at which each contribution can describe the subject matter is limited and a full review of their statuses, advances, challenges and perspectives cannot be fully accomplished. Also, magnetism, as a vibrant research field, is too diverse, so that a number of areas will not be adequately represented here, leaving space for further Roadmap editions in the future. However, this 2017 Magnetism Roadmap article can provide a frame that will enable the reader to judge where each subject and magnetism research field stands overall today and which directions it might take in the foreseeable future. The first material focused pillar of the 2017 Magnetism Roadmap contains five articles, which address the questions of atomic scale confinement, 2D, curved and topological magnetic materials, as well as materials exhibiting unconventional magnetic phase transitions. The second pillar also has five contributions, which are devoted to advances in magnetic characterization, magneto-optics and magneto-plasmonics, ultrafast magnetization dynamics and magnonic transport. The final and application focused pillar has four contributions, which present non-volatile memory technology, antiferromagnetic spintronics, as well as magnet technology for energy and bio-related applications. As a whole, the 2017 Magnetism Roadmap article, just as with its 2014 predecessor, is intended to act as a reference point and guideline for emerging research directions in modern magnetism.

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The 2017 Magnetism Roadmap

Nucleic Acid Biosensors: Recent Advances and Perspectives

Recent advances in superparamagnetic iron oxide nanoparticles (SPIONs) for in vitro and in vivo cancer nanotheranostics

Room temperature dielectric and magnetic properties of BiFeO3 samples, co-doped with magnetic Gd and non-magnetic Ti in place of Bi and Fe, respectively, were reported. The nominal compositions of Bi0.9Gd0.1Fe1–xTixO3 (x = 0.00-0.25) ceramics were synthesized by conventional solid state reaction technique. X-ray diffraction patterns revealed that the substitution of Fe by Ti induces a phase transition from rhombohedral to orthorhombic at x > 0.20. Morphological studies demonstrated that the average grain size was reduced from ∼1.5 μm to ∼200 nm with the increase in Ti content. Due to Ti substitution, the dielectric constant was stable over a wide range of high frequencies (30 kHz to 20 MHz) by suppressing the dispersion at low frequencies. The dielectric properties of the compounds are associated with their improved morphologies and reduced leakage current densities probably due to the lower concentration of oxygen vacancies in the compositions. Magnetic properties of Bi0.9Gd0.1Fe1–xTixO3 (x = 0.00-0.25) ceramics measured at room temperature were enhanced with Ti substitution up to 20% compared to that of pure BiFeO3 and Ti undoped Bi0.9Gd0.1FeO3 samples. The enhanced magnetic properties might be attributed to the substitution induced suppression of spiral spin structure of BiFeO3. An asymmetric shifts both in the field and magnetization axes of magnetization versus magnetic field curves was observed. This indicates the presence of exchange bias effect in these compounds notably at room temperature.

Room temperature dielectric and magnetic properties of Gd and Ti co-doped BiFeO3 ceramics

Room temperature dielectric and magnetic properties of BiFeO$_3$ samples, co-doped with magnetic Gd and non-magnetic Ti in place of Bi and Fe, respectively, were reported. The nominal compositions of Bi$_{0.9}$Gd$_{0.1}$Fe$_{1-x}$Ti$_x$O$_3$ (x = 0.00-0.25) ceramics were synthesized by conventional solid state reaction technique. X-ray diffraction patterns revealed that the substitution of Fe by Ti induces a phase transition from rhombohedral to orthorhombic at x $>$ 0.20. Morphological studies demonstrated that the average grain size was reduced from $\sim {~}$1.5 $\mu m$ to $\sim {~}$200 $nm$ with the increase in Ti content. Due to Ti substitution, the dielectric constant was stable over a wide range of high frequencies (30 kHz to 20 MHz) by suppressing the dispersion at low frequencies. The dielectric properties of the compounds are associated with their improved morphologies and reduced leakage current densities probably due to the lower concentration of oxygen vacancies in the compositions. Magnetic properties of Bi$_{0.9}$Gd$_{0.1}$Fe$_{1-x}$Ti$_x$O$_3$ (x = 0.00-0.25) ceramics measured at room temperature were enhanced with Ti substitution up to 20 $\%$ compared to that of pure BiFeO$_3$ and Ti undoped Bi$_{0.9}$Gd$_{0.1}$FeO$_3$ samples. The enhanced magnetic properties might be attributed to the substitution induced suppression of spiral spin structure of BiFeO$_3$. An asymmetric shifts both in the field and magnetization axes of magnetization versus magnetic field (M-H) curves was observed. This indicates the presence of exchange bias effect in these compounds notably at room temperature.

Room temperature dielectric and magnetic properties of Gd and Ti co-doped BiFeO$_{3}$ ceramics

Nanowires array modified electrode for enhanced electrochemical detection of nucleic acid.

A trilayer structure, which has weak exchange coupling and high active current, has been optimized emphasizing for high field-sensitivity planar Hall effect (PHE) sensor. To illustrate the high field sensitivity of the PHE sensor, three different structures are fabricated: a bilayer thin film Ta(3)/NiFe(10)/IrMn(10)/Ta(3) (nm), a spin-valve thin film Ta(3)/NiFe(10)/Cu(1.2)/NiFe(2)/IrMn(10)/Ta(3) (nm), and a trilayer thin film Ta(3)/NiFe(10)/Cu(0.12)/IrMn(10)/Ta(3) (nm). The characterized results reveal that the field sensitivity of PHE sensor based on trilayer thin film is about one order larger than that of bilayer and is about twice larger than that of spin-valve thin film. Moreover, in trilayer structure, the thinner spacer layer gives the better performance. When the nominal thickness of spacer Cu layer is the smallest, the PHE sensor exhibits the best performance, i.e., in this experiment, it is about 0.12 nm.

High field-sensitivity planar Hall sensor based on NiFe/Cu/IrMn trilayer structure

We present a simple technique to synthesize ultrafine nanoparticles directly from bulk multiferroic perovskite powder. The starting materials, which were ceramic pellets of the nominal compositions Bi0.9Gd0.1Fe1−xTixO3 (x = 0.00–0.20), were prepared initially by a solid state reaction technique, then ground into micrometer-sized powders and mixed with isopropanol or water in an ultrasonic bath. The particle size was studied as a function of sonication time with transmission electron microscopic imaging and electron diffraction that confirmed the formation of a large fraction of single-crystalline nanoparticles with a mean size of 11–13 nm. A significant improvement in the magnetic behavior of Bi0.9Gd0.1Fe1−xTixO3 nanoparticles compared to their bulk counterparts was observed at room temperature. This sonication technique may be considered as a simple and promising route to prepare ultrafine nanoparticles for functional applications.

Brajalal Sinha

Papers

Room temperature dielectric and magnetic properties of Gd and Ti co-doped BiFeO3 ceramics

Room temperature dielectric and magnetic properties of Gd and Ti co-doped BiFeO$_{3}$ ceramics

Nanowires array modified electrode for enhanced electrochemical detection of nucleic acid.

High field-sensitivity planar Hall sensor based on NiFe/Cu/IrMn trilayer structure

Simple top-down preparation of magnetic Bi0.9Gd0.1Fe1−xTixO3 nanoparticles by ultrasonication of multiferroic bulk material