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Elsevier eBooks · 2026-01-01

Bioapplications of magnetic nanobars: Nanowarming and bioidentification

Elsevier eBooks · 2026-01-01

Nondestructive Ferromagnetic Resonance Measurements Validate the Efficacy of a Seed Layer in Cobalt Magnetic Nanowire Fabrication

IEEE Transactions on Magnetics · 2025-01-08 · 2 citations

Magnetic nanowires (MNWs) have been proposed for use in numerous applications due to their tunability and scale, but due to the same tunability that makes MNWs so versatile, tight quality control is needed to make the transition from research labs to industry. Currently, template-assisted electrodeposition is a promising fabrication method, but there is no quick, low-cost method to effectively quantify fill factor (FF) of the templated wires. Here, we evaluate the efficacy of a copper seed layer to fabricate cobalt MNWs using quantitative ferromagnetic resonance (FMR). The deposition quality is assessed by FF and saturation magnetization (MS). First, the quality is evaluated by common, but qualitative or semi-quantitative methods, which are then compared to the quantitative values measured from FMR. The copper seed layer is demonstrated to improve FF while maintaining MNW quality. For the seeded sample, FMR measured FF at 12.3 ± 0.4%, with a MNW MS of 1.64 ± 0.10 T. For the sample without a seed, FMR measured FF at 9.0 ± 0.4% with a MNW MS of 1.62 ± 0.13 T. These quantitative measurements were corroborated by all the qualitative and semiquantitative results, indicating that nondestructive FMR is a viable method to quantify FF and quickly evaluate the quality of templated MNWs.

Effect of composition and two-step annealing on Ce-doped terbium iron garnets on Si

Optical Materials Express · 2025-05-16

Cerium-doped terbium iron garnet (CeTbIG) thin films with varying compositions and thicknesses were deposited to determine a garnet formation region. Both grain size and Faraday rotation (FR) increased in this region as the Ce content increased until 20% of the dodecahedral sites were occupied by Ce. The high Ce content was achieved by lowering the Fe ratio with respect to the total rare earth content. Above 20% Ce, the Faraday rotation was relatively independent of composition at -830 o /cm, which is similar in magnitude to positive Faraday rotation garnets, e.g.: + 600 o /cm for undoped TbIG. Next, we found that a two-step annealing method, involving a 400°C pre-anneal followed by higher temperatures, effectively reduced the maximum temperature from 900°C to 800°C without decreasing the Faraday rotation. Finally, a Si-integrated interferometer was simulated using the stable (+) and (-) Faraday rotation materials developed in this work. The simulation identified a Si-integrated Mach Zehnder Interferometers (MZI) with “push/pull” nonreciprocal phase shifts (NRPS) of opposite signs that enable mm-scale with zero external magnetic field (field-free).

Uniting Integration: Advancing RF Interconnect Technologies

IEEE Microwave Magazine · 2025-02-06 · 3 citations

Recently, advancing RF interconnect technologies for future 2.5D and 3D integration have been identified as an important game changer for energy efficient complex integrated circuit systems. Researchers are improving the performance of traditional interconnect technologies, such as wire bonds, and are exploring novel technologies as alternative interconnect solutions, such as stich chip and copper nanowire vias. Due to the high speed needs of 5G and 6G communication, interconnect operation needs to extend into the millimeter and sub-millimeter wave frequency range, which poses big challenges for designs with low loss and broad bandwidth. Herein, this review discusses and describes recent advances in interconnect technologies for wired and wireless RF applications. The research work is promising and shows a variety of methods to achieve low loss over a broad range of frequencies needed to truly enable design of energy efficient complex integrated circuit systems.

Characterization of Ferromagnetic Resonance Identification (Fmr-Id) Tag in Semi-Wireless Configuration

2025-04-14

This work characterizes a ferromagnetic resonance identification (FMR-ID) tag with magnetic nanowires (MNWs) in an anodized aluminum oxide (AAO) template using a semiwireless configuration. The MNWs exhibit distinct ferromagnetic resonance (FMR) frequencies under DC magnetic field variation. A benchmark test using an electromagnet (Emag) to generate a controlled low DC field and vector network analyzer (VNA) operating from 15-30 GHz, produced 5-bit data. To demonstrate portability, Emag is replaced with Disc-shaped permanent magnets (Pmag) that also validate a 5-bit data response. A semiwireless detection setup (a horn antenna and a metamaterial patch antenna (MMPA)) with lower bandwidth successfully retrieved 2bits of the data. Pmag and Emag FMR responses have similar slopes to the Kittel equation with an offset of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\sim 1 \text{GHz}$</tex>, believed to be due to DC field differences. These predictable responses demonstrate the feasibility of a semi-wireless FMR-ID system for use in enhanced RFID security applications.

Sustainable Manufacturing of Vertical Carbon Nanotube (CNT) Arrays Inside Insulating Nanoporous Membranes Using Nickel Magnetic Nanowires (MNWs)

ACS Applied Nano Materials · 2024-10-18 · 3 citations

Carbon nanotubes (CNTs) were successfully synthesized using industrial waste gases by chemical vapor deposition inside vertically oriented nanopores of insulating membranes. Importantly, the waste products from Fischer–Tropsch synthesis were used as the carbon source rather than typical purified sources, and this recycling of carbon is important for the sustainability of our environment. Specifically in this work, vertical CNT arrays were achieved using nickel (Ni) magnetic nanowires (MNWs) catalysts that were prepared by template electrochemical deposition inside 50 μm-thick nanoporous anodized aluminum oxide (AAO). Here, the nanopore diameter (20–200 nm) and Ni MNW length (45 and 25 μm) were varied to study the impact on CNT growth characteristics. Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, and field emission spectroscopy were used to characterize CNTs on Ni MNWs. For long MNWs (45 μm), the Ni catalyst was just below the AAO surface, so CNT diameters did not change appreciably with the MNW diameter. Alternatively, for short MNWs (25 μm), the carbon source gases had to diffuse into the AAO nanopores before reacting with the Ni catalyst, and both the CNT diameter and yield increased with the nanopore diameter. Highly crystalline CNTs were formed from particles of Ni catalyst, although for smaller diameter nanopores, the Ni catalyst particle could be blocked by template pore wall defects, resulting in subsequent amorphous nanofiber growth above the blocked particle. Optimally, CNT synthesis was observed for 25 μm MNWs grown in 80 nm AAO nanopores, maximizing field emission current at 480 μA/cm2 (at electric field 0.5 V/μm) with a turn-on field of 0.26 V/μm.

Interfacial magnetic characteristics of nearly compensated gadolinium iron garnet

Physical Review Materials · 2024-04-05 · 3 citations

Reports on spin Hall magnetoresistance, magnonic spin currents from thermal gradients, and spin transfer-torque magnetic random-access memory using compensated ferrimagnets largely discuss bulk magnetization but lack consideration of depth profiles or interfacial characteristics. Here, magnetic and structural characterization of profiles and interfaces was performed for nearly compensated gadolinium iron garnet (GdIG) thin films. X-ray diffraction and reciprocal space maps show that sputter deposited GdIG on Si is polycrystalline with the desired cubic garnet phase, and GdIG on gadolinium gallium garnet (GGG) is epitaxial with 0.06% compressive strain. Temperature-dependent magnetometry confirms the compensation temperatures of GGG/GdIG and Si/GdIG to be 285 and 260 K, respectively, both near room temperature. Interestingly, these measurements suggest the presence of unsaturated rare-earth moments, which result in a characteristic hysteresis between heating and cooling sequences in the magnetization-temperature curves at zero field. Depth-profile measurements from polarized neutron reflectometry (PNR) indicate up to 91% volume fraction in GdIG on Si. At the interface, PNR reveals a region containing magnetized Fe-doped GGG, a low-density GdIG at the GGG/GdIG interface, and a thin magnetically dead layer at the Si/GdIG interface. Cross-sectional transmission electron microscopy and energy dispersive x-ray spectroscopy confirm the assessment of PNR. The magnetic characteristics of interfacial regions are attributed to intermixing of Fe-Ga at the GGG/GdIG interface and the presence of amorphous Fe-Si at the Si/GdIG interface.

Ferromagnetic Resonance Identification (FMR-ID) under Low Magnetic Field for microwave RFID

2024-04-15 · 2 citations

A method for ferromagnetic resonance identification (FMR-ID), using magnetic nanowires (MNWs) made from cobalt-iron, is presented for sub-mmWave RFID applications. For use in a tag, a circuit comprised of a MNW chip with copper back placed above a grounded coplanar waveguide (GCPW) line is evaluated. According to simulation, minimal mismatch in the GCPW line and maximum FMR absorption in the MNW chip occurs when it is centered over the gap of the GCPW line. Five unique DC magnetic field strengths, between 0 and 0.2 T, have been applied perpendicular to the MNW chip. The detected FMR absorption is observed at five sub-mmWave frequencies between 20 and 30 GHz. This approach lays the foundation for five-bit tag identification addressing.

Predictions of optimal heating by magnetic reversal behavior of magnetic nanowires (MNWs) with different materials

International Journal of Hyperthermia · 2023-06-25 · 4 citations

Objective Magnetic nanowires (MNWs) are potential candidates for heating in biomedical applications that require rapid and uniform heating rates, such as warming cryopreserved organs and hyperthermia treatment of cancer cells. Therefore, it is essential to determine which materials and geometries will provide the optimal heating using available alternating magnetic fields (AMF).Method Micromagnetic simulations are used to investigate the heating ability of MNWs by predicting their hysteretic behavior. MNWs composed of iron (Fe), nickel (Ni), cobalt (Co) or permalloy (FeNi alloy, Py) with different diameters (10-200 nm) are simulated using object oriented micromagnetic framework (OOMMF).Results Hysteresis loops are obtained for each simulated MNW, and the 2D/3D magnetic moment map is simulated to show the reversal mechanism. The heating ability, in terms of specific loss power (SLP), is calculated from the area of the hysteresis loop times frequency for each MNW for comparison with others.Conclusion It is estimated that a theoretical optimal heating ability of 2730 W/g can be provided by isolated Co MNWs with 50 nm diameters using a typical AMF system that can supply 72 kA/m field amplitude and 50 kHz in frequency. Generalized correlation between coercivity and size/material of MNWs is provided as a guidance for researchers to choose the most appropriate MNW as a heater for their AMF system and vice versa.