Development Of Novel Magnetic Materials Research Articles

Unraveling dynamic Jahn-Teller effect and magnetism in FeTiF6×6H2O single crystal

Hydrated iron fluoridotitanate (FeTiF6 × 6 H2O) single crystals are fascinating magnetic materials with unique properties. To understand the underlying mechanisms, this study combines X-ray absorption near-edge structure (XANES) and X-ray magnetic circular dichroism (XMCD) techniques, complemented by density functional theory (DFT) calculations. Polarization-dependent X-ray absorption spectroscopy, encompassing XANES and XMCD, is a powerful technique for probing the local structures and magnetic properties of materials. It is element-selective, bulk-sensitive, and compatible with a wide range of experimental conditions. In this study, we used XANES and XMCD spectroscopies to investigate the local structures and magnetic properties of Fe and Ti in FeTiF6 × 6 H2O single crystals. XANES analysis revealed distinct local environments around Fe and Ti, providing insights into their coordination environments. Element-selective magnetization measurement at the Fe K-edge demonstrated that iron sites in the oxidation state Fe2+ have an unambiguous paramagnetic contribution to the magnetization along the b-axis. Notably, the absence of an XMCD signal at the Ti K-edge confirmed the absence of a magnetic moment in Ti atoms within the crystal. DFT calculations corroborate the experimental findings and provide insights into the electronic structure and magnetic interactions. The combined results provide a comprehensive understanding of the dynamic Jahn-Teller effect in FeTiF6 × 6 H2O single crystals, highlighting the significance of polarization-dependent X-ray absorption spectroscopy in unraveling the intricate magnetic behavior of such materials. This study contributes to the fundamental understanding of magnetism in these materials and paves the way for the development of novel magnetic materials with tailored properties.

Ac Susceptometry of 2D van der Waals Magnets Enabled by the Coherent Control of Quantum Sensors

Precision magnetometry is fundamental to the development of novel magnetic materials and devices. Recently, the nitrogen-vacancy (NV) center in diamond has emerged as a promising probe for static magnetism in two-dimensional (2D) van der Waals materials, capable of quantitative imaging with nanoscale spatial resolution. However, the dynamic character of magnetism, crucial for understanding the magnetic phase transition and achieving technological applications, has rarely been experimentally accessible in single 2D crystals. Here, we coherently control the NV center’s spin precession to achieve ultrasensitive, quantitative ac susceptometry of a 2D ferromagnet. Combining dc hysteresis with ac susceptibility measurements varying temperature, field, and frequency, we illuminate the formation, mobility, and consolidation of magnetic domain walls in few-layer CrBr3. We show that domain wall mobility is enhanced in ultrathin CrBr3, with minimal decrease for excitation frequencies exceeding hundreds of kilohertz, and is influenced by the domain morphology and local pinning of the flake. Our technique extends NV magnetometry to the multifunctional ac and dc magnetic characterization of wide-ranging spintronic materials at the nanoscale.10 MoreReceived 17 May 2021Accepted 23 August 2021DOI:https://doi.org/10.1103/PRXQuantum.2.030352Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasQuantum sensingPhysical Systems2-dimensional systemsNitrogen vacancy centers in diamondTechniquesAC susceptibility measurementsCondensed Matter, Materials & Applied Physics

Demonstration of Ru as the 4th ferromagnetic element at room temperature

Development of novel magnetic materials is of interest for fundamental studies and applications such as spintronics, permanent magnetics, and sensors. We report on the first experimental realization of single element ferromagnetism, since Fe, Co, and Ni, in metastable tetragonal Ru, which has been predicted. Body-centered tetragonal Ru phase is realized by use of strain via seed layer engineering. X-ray diffraction and electron microscopy confirm the epitaxial mechanism to obtain tetragonal phase Ru. We observed a saturation magnetization of 148 and 160 emu cm−3 at room temperature and 10 K, respectively. Control samples ensure the ferromagnetism we report on is from tetragonal Ru and not from magnetic contamination. The effect of thickness on the magnetic properties is also studied, and it is observed that increasing thickness results in strain relaxation, and thus diluting the magnetization. Anomalous Hall measurements are used to confirm its ferromagnetic behavior.

Magnetic Properties of Cobalt Nanowires and Nanotubes

Development of novel magnetic materials has played an important role in modern day science and technology. Nanomagnetism research not only sparks interests in fundamental physics, but also renders promising technological applications. Ferromagnetic Co nanowires, synthesized via low voltage electrodeposition method. High resolution transmission electron microscopy and x-ray diffraction results show that the nanowires are uniform in size, and consist predominantly hcp structure with the magnetocrystalline easy axis (c-axis) perpendicular to the wire axis. SQUID measurement illustrates the dominance of shape anisotropy, manifested by the weak temperature dependence of the enhanced coercive field along the wire axis. Furthermore, the magnetic domain structures of individual, segmented or multiple nanowires are studied via magnetic force microscopy. It shows a strong dipole at the ends of the wire, together with a spatial magnetization modulation along the wire with a period around 700 nm. Based on theoretical modeling, such intrinsic modulation originates from the competition between the magnetocrystalline polarization along the easy axis and the shape anisotropy along the wire axis. Low temperature magnetoresistance measurement shows irreversible magnetization switching in addition to the anisotropic behavior due to magnetization orientation dependent electron scattering.On the other hand, Cobalt nanotube arrays embedded in hexagonally ordered anodic aluminum oxide templates are fabricated by direct electrodeposition with low current density under several mA/cm2. The wall thickness is about 15 nm and outer diameters are in accordance with pore diameter around 80 nm. Nearly 100% filling rate is achieved which benefits from the through pores which enable the efficient penetration of electrolyte. Transmission electron microscopy and selected-area electron diffraction are performed to show that the nanotubes are predominantly hcp single crystals with c-axis (easy axis) perpendicular to the tube axis. SQUID and MFM results indicate that the magnetization follows a circumferential direction around the tube, which is manifested in the weak magnetic signal in the MFM imaging as well as a sheared hysteresis dependence for field applied along the tube axis. This phenomenon has been confirmed by theoretical modeling taking into account the magnetocrystalline, shape demagnetization and magnetic exchange energies.

Principles and emerging applications of nanomagnetic materials in medicine

The development of nanometer-scale magnetic materials for biomedical applications spans the interface between the physical sciences and biology. Applications of these materials are rapidly becoming important in medicine and enable targeted therapies and diagnostics. At the same time, specific applications add focus to the development of novel magnetic materials and facilitate a deeper understanding of the physical mechanisms behind their function. This review presents a broad, nontechnical overview of the basis of magnetism in materials at the nanometer scale and describes how these materials are created, characterized, and used. Specific emerging applications in medical diagnostics and therapies are discussed, including cancer cell targeting for thermal ablation, tissue engineering, and three-dimensional noninvasive molecular imaging. Challenges in these fields are discussed, including the toxicity and delivery of magnetic nanomaterials and the sensitivity of imaging and therapeutic techniques. The development of novel nanomagnetic nanomaterials should continue to accelerate as new applications are identified and researchers uncover new mechanisms to increase and modulate magnetism at the nanometer scale.

The Research and Development of Novel Magnetic Material and Magnetic Core Used in Planar Transformer

The novel soft magnetic materials and magnetic core structure used in planar transformer have been studied. The frequency, electrical and structure feature of the planar transformer with matrix structure was described. Then the novel magnetic materials used in the planar transformer were discussed, which were very different from ferrite block. The silicon steel strip was first represented, the magnetic characteristic of which was related to its geometric dimension, working frequency and the component. The microcrystallite alloy and amorphous alloy magnetic materials were then indicated, including iron-base nanocrystal and cobalt-base amorphous alloy. The magnetic materials of the above amorphous alloy and microcrystallite alloy were compared respectively. These soft magnetic materials could be used as the magnetic core in planar transformer, and the magnetic core could be composed of thin strip and line. The structure of magnetic core was flexible, which could benefit the planar transformer to reduce its volume. The development and trendy of novel magnetic materials and magnetic core in planar transformer were analyzed and discussed in this paper.

Giant magnetoimpedance in layered composite micro-wires for high-sensitivity magnetic sensor applications

Currently, the design and development of novel magnetic materials with optimized properties is of relevance to study new phenomena and to use them for multifunctional applications of sensor technologies and magnetoelectronic devices. In this letter, we present a detailed investigation of giant magnetoimpedance (GMI) effect in layered magnetic microwires. A new family of layered microwire composite materials was fabricated by using rapidly quenching and coating techniques. The experimental measurements were performed using an impedance analyzer (HP 4191A) in the frequency range of 100 – 1000 MHz and a varying applied dc magnetic field within ± 300 Oe. Interestingly, the GMI ratio and magnetic-field sensitivity reached the largest values of 3200 and 2400%/Oe at a resonance frequency of 890.15 MHz for layered Co-rich microwire sample, respectively. These results are very ideal for the development of a new family of ultra-sensitive and high-frequency magnetic sensors. Finally, the layered composite magnetic micro-wire developed with enhanced sensitivity performance can be ideally used as sensing elements in magnetic sensor technologies.