scholarly journals Micromagnetic Simulations of Submicron Vortex Structures for the Detection of Superparamagnetic Labels

Sensors ◽  
2020 ◽  
Vol 20 (20) ◽  
pp. 5819
Author(s):  
Lukas Wetterau ◽  
Claas Abert ◽  
Dieter Suess ◽  
Manfred Albrecht ◽  
Bernd Witzigmann
Keyword(s):  
Electric Potential ◽  
Giant Magnetoresistance ◽  
Spin Diffusion ◽  
Magnetic Vortex ◽  
Electric Response ◽  
Stray Field ◽  
Soft Magnetic ◽  
Micromagnetic Simulations ◽  
Gmr Sensor ◽  
Magnetization Change

We present a numerical investigation on the detection of superparamagnetic labels using a giant magnetoresistance (GMR) vortex structure. For this purpose, the Landau–Lifshitz–Gilbert equation was solved numerically applying an external z-field for the activation of the superparamagnetic label. Initially, the free layer’s magnetization change due to the stray field of the label is simulated. The electric response of the GMR sensor is calculated by applying a self-consistent spin-diffusion model to the precomputed magnetization configurations. It is shown that the soft-magnetic free layer reacts on the stray field of the label by shifting the magnetic vortex orthogonally to the shift direction of the label. As a consequence, the electric potential of the GMR sensor changes significantly for label shifts parallel or antiparallel to the pinning of the fixed layer. Depending on the label size and its distance to the sensor, the GMR sensor responds, changing the electric potential from 26.6 mV to 28.3 mV.

scholarly journals A tandem giant magnetoresistance assay for one-shot quantification of clinically relevant concentrations of N-terminal pro-B-type natriuretic peptide in human blood

2021 ◽  
Author(s):  
Fanda Meng ◽  
Weisong Huo ◽  
Jie Lian ◽  
Lei Zhang ◽  
Xizeng Shi ◽  
...  
Keyword(s):  
Detection Limit ◽  
Giant Magnetoresistance ◽  
Dynamic Range ◽  
Point Of Care ◽  
Sample Volume ◽  
Small Sample ◽  
Broad Dynamic Range ◽  
Gmr Sensors ◽  
Gmr Sensor ◽  
Sample Volume Requirement

AbstractWe report a microfluidic sandwich immunoassay constructed around a dual-giant magnetoresistance (GMR) sensor array to quantify the heart failure biomarker NT-proBNP in human plasma at the clinically relevant concentration levels between 15 pg/mL and 40 ng/mL. The broad dynamic range was achieved by differential coating of two identical GMR sensors operated in tandem, and combining two standard curves. The detection limit was determined as 5 pg/mL. The assay, involving 53 plasma samples from patients with different cardiovascular diseases, was validated against the Roche Cobas e411 analyzer. The salient features of this system are its wide concentration range, low detection limit, small sample volume requirement (50 μL), and the need for a short measurement time of 15 min, making it a prospective candidate for practical use in point of care analysis.

scholarly journals Micromagnetic Simulations of Discrete Track Media Consisting of Soft Magnetic Fillings

2009 ◽  
Vol 33 (3) ◽  
pp. 163-166
Author(s):  
C. M. Loke ◽  
S. Greaves ◽  
H. Muraoka ◽  
J. Yasumori ◽  
Y. Sonobe
Keyword(s):  
Soft Magnetic ◽  
Micromagnetic Simulations ◽  
Discrete Track

scholarly journals CPP-GMR Performance of Electrochemically Synthesized Co/Cu Multilayered Nanowire Arrays with Extremely Large Aspect Ratio

Nanomaterials ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 5
Author(s):  
Himeyo Kamimura ◽  
Masamitsu Hayashida ◽  
Takeshi Ohgai
Keyword(s):  
Aspect Ratio ◽  
Giant Magnetoresistance ◽  
Spin Diffusion ◽  
Nanowire Arrays ◽  
Diffusion Limit ◽  
Anodized Aluminum ◽  
Anodized Aluminum Oxide ◽  
Sputter Deposited ◽  
Multilayered Nanowires

Anodized aluminum oxide (AAO) films, which have numerous nanochannels ca. 75 nm in diameter, D and ca. 70 µm in length, L (ca. 933 in aspect ratio, L/D), were used as a template material for growing Co/Cu multilayered nanowire arrays. The multilayered nanowires with alternating Cu layer and Co layers were synthesized by using an electrochemical pulsed-potential deposition technique. The thickness of the Cu layer was adjusted from ca. 2 to 4 nm while that of the Co layer was regulated from ca. 13 to 51 nm by controlling the pulsed potential parameters. To get a Co/Cu multilayered nanowire in an electrochemical in-situ contact with a sputter-deposited Au thin layer, the pulsed potential deposition was continued up to ca. 5000 cycles until the nanowire reached out toward the surface of AAO template. Current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) effect reached up to ca. 23.5% at room temperature in Co/Cu multilayered nanowires with ca. 3500 Co/Cu bilayers (Cu: 1.4 nm and Co: 18.8 nm). When decreasing the thickness of Co layer, the CPP-GMR value increased due to the Valet–Fert model in the long spin diffusion limit.

3-D Simulations of Micromagnetic Transition Structures in Vortex Asymmetric Domain Walls

2014 ◽  
Vol 215 ◽  
pp. 421-426 ◽  
Author(s):  
Vladimir V. Zverev ◽  
Mikhail N. Dubovik ◽  
Boris N. Filippov
Keyword(s):  
Nonlinear Waves ◽  
Domain Walls ◽  
Three Dimensional ◽  
Magnetic Films ◽  
Soft Magnetic ◽  
Micromagnetic Simulations ◽  
Plane Anisotropy ◽  
Transition Structures ◽  
Asymmetric Domain Walls ◽  
Soft Magnetic Films

The three-dimensional transition structures in the vortex asymmetric domain walls existing in magnetically uniaxial soft magnetic films with in-plane anisotropy are studied by micromagnetic simulations. It is shown that interaction of closely spaced transition structures results in various dynamical scenarios including vortex-antivortex annihilations, creation and annihilation of singular (Bloch) points, and excitation of nonlinear waves.

scholarly journals Evaluation of In-Flow Magnetoresistive Chip Cell—Counter as a Diagnostic Tool

Biosensors ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 105 ◽  
Author(s):  
Manon Giraud ◽  
François-Damien Delapierre ◽  
Anne Wijkhuisen ◽  
Pierre Bonville ◽  
Mathieu Thévenin ◽  
...  
Keyword(s):  
Giant Magnetoresistance ◽  
Limit Of Detection ◽  
Malignant Cell ◽  
Elisa Test ◽  
Great Sensitivity ◽  
Actual System ◽  
Whole Cells ◽  
Gmr Sensors ◽  
Gmr Sensor ◽  
Sensor Detection

Inexpensive simple medical devices allowing fast and reliable counting of whole cells are of interest for diagnosis and treatment monitoring. Magnetic-based labs on a chip are one of the possibilities currently studied to address this issue. Giant magnetoresistance (GMR) sensors offer both great sensitivity and device integrability with microfluidics and electronics. When used on a dynamic system, GMR-based biochips are able to detect magnetically labeled individual cells. In this article, a rigorous evaluation of the main characteristics of this magnetic medical device (specificity, sensitivity, time of use and variability) are presented and compared to those of both an ELISA test and a conventional flow cytometer, using an eukaryotic malignant cell line model in physiological conditions (NS1 murine cells in phosphate buffer saline). We describe a proof of specificity of a GMR sensor detection of magnetically labeled cells. The limit of detection of the actual system was shown to be similar to the ELISA one and 10 times higher than the cytometer one.

Biosensor Based on Giant Magnetoresistance Material

2010 ◽  
Vol 1 (3) ◽  
pp. 1-15 ◽  
Author(s):  
Mitra Djamal
Keyword(s):  
Giant Magnetoresistance ◽  
Large Scale ◽  
Single Chip ◽  
Biomolecule Detection ◽  
Novel Approach ◽  
Large Scale Integration ◽  
Gmr Sensors ◽  
Gmr Sensor ◽  
Scale Integration ◽  
The Magnetic Field

In recent years, giant magnetoresistance (GMR) sensors have shown a great potential as sensing elements for biomolecule detection. The resistance of a GMR sensor changes with the magnetic field applied to the sensor, so that a magnetically labeled biomolecule can induce a signal. Compared with the traditional optical detection that is widely used in biomedicine, GMR sensors are more sensitive, portable, and give a fully electronic readout. In addition, GMR sensors are inexpensive and the fabrication is compatible with the current VLSI (Very Large Scale Integration) technology. In this regard, GMR sensors can be easily integrated with electronics and microfluidics to detect many different analytes on a single chip. In this article, the authors demonstrate a comprehensive review on a novel approach in biosensors based on GMR material.

scholarly journals The Role of Surface Topography on Deformation-Induced Magnetization under Inhomogeneous Elastic-Plastic Deformation

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1518 ◽  
Author(s):  
Nadja Sonntag ◽  
Birgit Skrotzki ◽  
Robert Stegemann ◽  
Peter Löwe ◽  
Marc Kreutzbruck
Keyword(s):  
Plastic Deformation ◽  
Ferromagnetic Material ◽  
Image Correlation ◽  
Stray Field ◽  
Inhomogeneous Deformation ◽  
Elastic Plastic ◽  
Lift Off ◽  
Gmr Sensor ◽  
Magnetic States ◽  
Field Formation

It is widely accepted that the magnetic state of a ferromagnetic material may be irreversibly altered by mechanical loading due to magnetoelastic effects. A novel standardized nondestructive testing (NDT) technique uses weak magnetic stray fields, which are assumed to arise from inhomogeneous deformation, for structural health monitoring (i.e., for detection and assessment of damage). However, the mechanical and microstructural complexity of damage has hitherto only been insufficiently considered. The aim of this study is to discuss the phenomenon of inhomogeneous “self-magnetization” of a polycrystalline ferromagnetic material under inhomogeneous deformation experimentally and with stronger material-mechanical focus. To this end, notched specimens were elastically and plastically deformed. Surface magnetic states were measured by a three-axis giant magnetoresistant (GMR) sensor and were compared with strain field (digital image correlation) and optical topography measurements. It is demonstrated that the stray fields do not solely form due to magnetoelastic effects. Instead, inhomogeneous plastic deformation causes topography, which is one of the main origins for the magnetic stray field formation. Additionally, if not considered, topography may falsify the magnetic signals due to variable lift-off values. The correlation of magnetic vector components with mechanical tensors, particularly for multiaxial stress/strain states and inhomogeneous elastic-plastic deformations remains an issue.

Correlation Exchange Length in Nanocrystalline Soft Magnetic Materials Characterized by Electron Holography

2005 ◽  
Vol 475-479 ◽  
pp. 4021-4028
Author(s):  
Youhui Gao ◽  
Daisuke Shindo
Keyword(s):  
Elevated Temperature ◽  
Decay Constant ◽  
Soft Magnetic Materials ◽  
Stray Field ◽  
Electron Holography ◽  
Soft Magnetic ◽  
Ripple Structure ◽  
Effective Exchange ◽  
Magnetic Hardness ◽  
Exchange Length

Magnetic ripple structure of Fe84Nb7B9 is studied by electron holography. The correlation exchange length, effective exchange and anisotropy constants are estimated from a field dependence of ripple wavelength. The function of ripple theory is adjusted with a decay constant, which reflects influence of stray field on the ripple structure. A magnetic hardness at elevated temperature is also observed and analyzed.

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