Biogenic magnetite and magnetic sensitivity in organisms -- from magnetic bacteria to pigeons

2005 ◽  
Vol 41 (4) ◽  
pp. 295-304 ◽  
Keyword(s):  
Biogenic Magnetite ◽  
Magnetic Sensitivity

High Resolution Current Imaging by Direct Magnetic Field Sensing

2003 ◽  
Author(s):  
S.I. Woods ◽  
Nesco M. Lettsome ◽  
A.B. Cawthorne ◽  
L.A. Knauss ◽  
R.H. Koch
Keyword(s):  
Magnetic Field ◽  
High Resolution ◽  
Spatial Resolution ◽  
Great Promise ◽  
Magnetoresistive Sensor ◽  
Magnetic Sensitivity ◽  
Current Lines ◽  
Scanning Squid ◽  
Scanning Fiber ◽  
Ferromagnetic Probe

Abstract Two types of magnetic microscopes have been investigated for use in high resolution current mapping. The scanning fiber/SQUID microscope uses a SQUID sensor coupled to a nanoscale ferromagnetic probe, and the GMR microscope employs a nanoscale giant magnetoresistive sensor. Initial scans demonstrate that these microscopes can resolve current lines less than 10 µm apart with edge resolution of 1 µm. These types of microscopes are compared with the performance of a standard scanning SQUID microscope and with each other with respect to spatial resolution and magnetic sensitivity. Both microscopes show great promise for identifying current defects in die level devices.

scholarly journals Magnetoelastic Coupling and Delta-E Effect in Magnetoelectric Torsion Mode Resonators

Sensors ◽  
2021 ◽  
Vol 21 (6) ◽  
pp. 2022
Author(s):  
Benjamin Spetzler ◽  
Elizaveta V. Golubeva ◽  
Ron-Marco Friedrich ◽  
Sebastian Zabel ◽  
Christine Kirchhof ◽  
...  
Keyword(s):  
Low Frequency ◽  
High Sensitivity ◽  
Element Model ◽  
Mode Number ◽  
Frequency Change ◽  
General Description ◽  
Resonance Modes ◽  
Field Sensor ◽  
Magnetic Sensitivity ◽  
Bending Modes

Magnetoelectric resonators have been studied for the detection of small amplitude and low frequency magnetic fields via the delta-E effect, mainly in fundamental bending or bulk resonance modes. Here, we present an experimental and theoretical investigation of magnetoelectric thin-film cantilevers that can be operated in bending modes (BMs) and torsion modes (TMs) as a magnetic field sensor. A magnetoelastic macrospin model is combined with an electromechanical finite element model and a general description of the delta-E effect of all stiffness tensor components Cij is derived. Simulations confirm quantitatively that the delta-E effect of the C66 component has the promising potential of significantly increasing the magnetic sensitivity and the maximum normalized frequency change ∆fr. However, the electrical excitation of TMs remains challenging and is found to significantly diminish the gain in sensitivity. Experiments reveal the dependency of the sensitivity and ∆fr of TMs on the mode number, which differs fundamentally from BMs and is well explained by our model. Because the contribution of C11 to the TMs increases with the mode number, the first-order TM yields the highest magnetic sensitivity. Overall, general insights are gained for the design of high-sensitivity delta-E effect sensors, as well as for frequency tunable devices based on the delta-E effect.

scholarly journals Reductive dissolution of biogenic magnetite

2020 ◽  
Vol 72 (1) ◽  
Author(s):  
Toshitsugu Yamazaki
Keyword(s):  
Japan Sea ◽  
Depth Interval ◽  
Reductive Dissolution ◽  
Magnetic Minerals ◽  
Specific Chemical ◽  
Biogenic Magnetite ◽  
Transmission Electron ◽  
Dissolution Zone ◽  
Central Ridge ◽  
Redox Boundary

Abstract Reductive dissolution of magnetite is known to occur below the Fe-redox boundary in sediments. In this study, detailed processes associated with biogenic magnetite dissolution are documented. A sediment core from the Japan Sea was used for this purpose, in which reductive dissolution of magnetic minerals is known to start at depths of about 1.15 m and is mostly complete within a depth interval of about 0.35 m. Using first-order reversal curve diagrams, preferential dissolution of biogenic magnetite within this interval is estimated from the observation that a narrow peak that extends along the coercivity axis (central ridge), which is indicative of biogenic magnetite, diminishes downcore. Transmission electron microscopy is used to demonstrate that the sediments contain three magnetofossil morpho-types: octahedra, hexagonal prisms, and bullet-shaped forms. Within the reductive dissolution zone, partially etched crystals are commonly observed. With progressive dissolution, the proportion of bullet-shaped magnetofossils decreases, whereas hexagonal prisms become more dominant. This observation can be explained by the differences in resistance to dissolution among crystal planes of magnetite and the differences in surface area to volume ratios. Magnetofossil morphology may reflect the preference of magnetotactic bacterial lineages for inhabiting specific chemical environments in sediments. However, it could also reflect alteration of the original morphological compositions during reductive diagenesis, which should be considered when using magnetofossil morphology as a paleoenvironmental proxy.

scholarly journals Manganese in biogenic magnetite crystals from magnetotactic bacteria

2009 ◽  
Vol 292 (2) ◽  
pp. 250-253 ◽  
Author(s):  
Carolina N. Keim ◽  
Ulysses Lins ◽  
Marcos Farina
Keyword(s):  
Magnetotactic Bacteria ◽  
Biogenic Magnetite

Chitosan-based synthesis of magnetically-driven nanocomposites with biogenic magnetite core, controlled silver size, and high antimicrobial activity

2012 ◽  
Vol 14 (9) ◽  
pp. 2550 ◽  
Author(s):  
Zdenka Marková ◽  
Karolína Šišková ◽  
Jan Filip ◽  
Klára Šafářová ◽  
Robert Prucek ◽  
...  
Keyword(s):  
Antimicrobial Activity ◽  
High Antimicrobial Activity ◽  
Biogenic Magnetite

Increase of Magnetic Sensitivity of Magnetically Controlled MEMS Switches

MRS Advances ◽  
2016 ◽  
Vol 1 (34) ◽  
pp. 2393-2399
Author(s):  
Sergey M. Karabanov ◽  
Dmitry V. Suvorov ◽  
Gennady P. Gololobov ◽  
Dmitry Y. Tarabrin ◽  
Evgeny V. Slivkin
Keyword(s):  
Magnetic Field ◽  
Research Results ◽  
Mems Switches ◽  
Field Concentrator ◽  
Magnetic Sensitivity ◽  
Sensitivity Increase

ABSTRACTThe paper presents the research results of influence of various parameters of magnetic field concentrator geometry on sensitivity of magnetically controlled MEMS switches. It is shown that magnetic sensitivity increases with the growth of the magnetic concentrator width and practically does not depend on its length. It is established that dependence of magnetic sensitivity on the overlap length of the ferromagnetic flexible contact-concentrator has a minimum corresponding to 2-3 lengths of the contact gap. Recommendations on sensitivity increase of magnetically controlled MEMS switches are provided.

X-ray radiation increases the magnetic sensitivity of planar-diffusion triacs

2002 ◽  
Vol 28 (10) ◽  
pp. 812-814
Author(s):  
S. I. Vorontsov ◽  
S. B. Baklanov ◽  
N. T. Gurin ◽  
S. G. Novikov
Keyword(s):  
X Ray ◽  
Magnetic Sensitivity
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