Iron deficient BaNixMnxFe12−2xO19 (x = 0.0–0.5) hexagonal plates: single-domain magnetic structure and dielectric properties

The effect of microstructure on the efficiency of shielding or shunting of the magnetic flux by permalloy shields was investigated in the present work. For this purpose, the FeNi shielding coatings with different grain structures were obtained using stationary and pulsed electrodeposition. The coatings’ composition, crystal structure, surface microstructure, magnetic domain structure, and shielding efficiency were studied. It has been shown that coatings with 0.2–0.6 µm grains have a disordered domain structure. Consequently, a higher value of the shielding efficiency was achieved, but the working range was too limited. The reason for this is probably the hindered movement of the domain boundaries. Samples with nanosized grains have an ordered two-domain magnetic structure with a permissible partial transition to a superparamagnetic state in regions with a grain size of less than 100 nm. The ordered magnetic structure, the small size of the domain, and the coexistence of ferromagnetic and superparamagnetic regions, although they reduce the maximum value of the shielding efficiency, significantly expand the working range in the nanostructured permalloy shielding coatings. As a result, a dependence between the grain and domain structure and the efficiency of magnetostatic shielding was found.

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Hexagonal microstructure, magnetic and dielectric properties of iron deficient BaNixZnxFe12−2xO19 (x = 0.0−0.5) hexaferrites

Applied Physics A ◽

10.1007/s00339-021-05001-x ◽

2021 ◽

Vol 127 (11) ◽

Author(s):

D. Chandra Sekhar ◽

T. Subba Rao ◽

K. Chandra Babu Naidu

Keyword(s):

Dielectric Properties ◽

Iron Deficient ◽

Magnetic And Dielectric Properties

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Dielectric Properties of Single Domain Crystals of BaTiO3at Microwave Frequencies

Physical Review ◽

10.1103/physrev.109.1091 ◽

1958 ◽

Vol 109 (4) ◽

pp. 1091-1093 ◽

Cited By ~ 79

Author(s):

T. S. Benedict ◽

J. L. Durand

Keyword(s):

Dielectric Properties ◽

Single Domain ◽

Microwave Frequencies

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A quantitative assessment of torque-transducer models for magnetoreception

Journal of The Royal Society Interface ◽

10.1098/rsif.2009.0435.focus ◽

2010 ◽

Vol 7 (suppl_2) ◽

Cited By ~ 70

Author(s):

Michael Winklhofer ◽

Joseph L. Kirschvink

Keyword(s):

Magnetic Field ◽

Magnetic Structure ◽

Magnetic Particles ◽

Single Domain ◽

Nerve Signal ◽

The Common ◽

Torque Transducer ◽

Behavioural Experiments ◽

Pulsed Fields ◽

Vestibular Organs

Although ferrimagnetic material appears suitable as a basis of magnetic field perception in animals, it is not known by which mechanism magnetic particles may transduce the magnetic field into a nerve signal. Provided that magnetic particles have remanence or anisotropic magnetic susceptibility, an external magnetic field will exert a torque and may physically twist them. Several models of such biological magnetic-torque transducers on the basis of magnetite have been proposed in the literature. We analyse from first principles the conditions under which they are viable. Models based on biogenic single-domain magnetite prove both effective and efficient, irrespective of whether the magnetic structure is coupled to mechanosensitive ion channels or to an indirect transduction pathway that exploits the strayfield produced by the magnetic structure at different field orientations. On the other hand, torque-detector models that are based on magnetic multi-domain particles in the vestibular organs turn out to be ineffective. Also, we provide a generic classification scheme of torque transducers in terms of axial or polar output, within which we discuss the results from behavioural experiments conducted under altered field conditions or with pulsed fields. We find that the common assertion that a magnetoreceptor based on single-domain magnetite could not form the basis for an inclination compass does not always hold.

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