FERRITE MAGNETS : A VIDEO ESSAY

Audiopedia
Published on Oct 11, 2015
A ferrite is a type of ceramic compound composed of iron oxide combined

chemically with one or more additional metallic elements. They are both

electrically nonconductive and ferrimagnetic, meaning they can be magnetized

or attracted to a magnet. Ferrites can be divided into two families based on

their magnetic coercivity, their resistance to being demagnetized. Hard

ferrites have high coercivity; they are difficult to demagnetize. They are

used to make magnets, for devices such as refrigerator magnets, loudspeakers

and small electric motors. Soft ferrites have low coercivity. They are used in

the electronics industry to make ferrite cores for inductors and transformers,

and in various microwave components. Yogoro Kato and Takeshi Takei of the

Tokyo Institute of Technology invented ferrite in 1930.


This video
Transcript is targeted to blind users.

Attribution:
Article text available under CC-BY-SA
Creative Commons image source in video
Category
Education


Add a public comment...



a ferrite is a type of ceramic compound
composed of iron oxide combined
chemically with one or more additional
metallic elements they are both
electrically non-conductive and
ferromagnetic meaning they can be
magnetized or attracted to a magnet
ferrets can be divided into two families
based on their magnetic guseva T their
resistance to being demagnetized hard
ferrets have high guseva t they are
difficult to demagnetize they are used
to make magnets for devices such as
refrigerator magnets loudspeakers and
small electric motors soft ferrets have
low COO civet e they're used in the
electronics industry to make ferrite
calls for inductors and transformers and
in various microwave components yogi
Ricardo and Takeshi decay of the Tokyo
Institute of Technology invented ferrite
in 1930 composition and properties
ferrets are usually non conductive
ferromagnetic ceramic compounds derived
from iron oxides such as hematite or
magnetite as well as oxides of other
metals ferrets are like most of the
other ceramics hard and brittle many
ferrets are spinels with the formula a
b204 where a and B represent various
metal cations usually including iron fay
spinel ferrites usually adopt a crystal
motif consisting of cubic close packed
oxides with a cations occupying one
eighth of the tetrahedral holes and B
cations occupying half of the octahedral
holes if one-eighth of the tetrahedral
holes are occupied by B cation then
one-fourth of the octahedral sites are
occupied by a cation and the other 1/4
by B cation and it's called the inverse
spinel structure it's also possible to
have mixed structure spin-off rights
with formula m2 plus 1 I fait 3 plus I
m2 plus I PHA 3 plus 2 I know full where
I is the degree of inversion the
magnetic material known as said n PHA is
the formulas en fait 204 with fait 3
plus occupying the octahedral sites and
Zn 2 + occupy the tetrahedral sites it's
an example of normal structure spinel
ferrite some ferrite sub hex
crystal structure like barium and
strontium ferrite parfait 12 o 19 and SR
fait 12 o 19 in terms of their magnetic
properties the different ferrets are
often classified as soft or hard which
refers to their low or high magnetic
guseva T as follows equal soft ferrite
sequel's ferrite that are used in
transformer or electro magnetic cores
contain nickel zinc and/or manganese
compounds they have a low cous avati and
are called soft ferrites the low kusa VT
means the materials magnetization can
easily reverse direction without
dissipating much energy while the
materials high resistivity prevents eddy
currents in the core another source of
energy loss because of their
comparatively low losses at high
frequencies they are extensively used in
the cause of RF transformers and
inductors in applications such as
switched-mode power supplies and loop
stick antennas used in am radios the
most common soft ferrites are manganese
zinc ferrite say two o 4 MN ZN have
higher permeability and saturation
induction than ni zan nickel zinc
ferrite fato 4 ni zan ferrets exhibit
higher resistivity than mm ZN and are
therefore more suitable for frequencies
above 1 megahertz for applications below
5 megahertz MN ZN ferrets are used above
that ni ZN is the usual choice the
exception is with common mode and
doctors wear the threshold of choice is
at 17 mega Hertz equals hard ferrite
sequel's in contrast permanent ferrite
magnets are made of hard ferrite s--
which have a high passivity and high REE
maintenance after magnetization iron
oxide and barium or strontium carbonate
are used in manufacturing of hard
ferrite magnets the Haiku civet e means
the materials are very resistant to
becoming demagnetized an essential
characteristic for a permanent magnet
they also have high magnetic
permeability these so-called ceramic
magnets are cheap and are widely used in
household prod
such as refrigerator magnets the maximum
magnetic field B is about 0.35 Tesla and
the magnetic field strength H is about
30 to 160 km per turns per meter the
density of ferrite magnets is about 5
grams per centimeter 3 the most common
hard ferrite Tsar strontium ferrite srf
a 12 o 19 used in small electric motors
microwave devices recording media
magneto-optic media telecommunication
and electronic industry barium ferrite
barf a 12 o 19 a common material for
permanent magnet applications barium
ferrite so robust ceramics that are
generally stable to moisture and
corrosion resistant they are euston for
example loudspeaker magnets and is a
medium for magnetic recording for
example on magnetic stripe cards cobalt
ferrite CO 80204 used in some media for
magnetic recording production ferrets
are produced by heating a mixture of
finely powdered precursors pressed into
a mold during the heating process
calcination of carbonates occurs MCO 3
amo plus CO 2 the oxides of barium and
strontium are typically supplied as
their carbonates Barco 3 or SR Co 3 the
resulting mixture of oxides undergoes
sintering sintering is a high
temperature process similar to the
firing of ceramic where afterwards the
cool product is milled to particles
smaller than 2 a micrometer small enough
that each particle consists of a single
magnetic domain next the powder is
pressed into a shape dried and re
sintered the shaping may be performed in
an external magnetic field in order to
achieve a preferred orientation of the
particles small and geometrically easy
shapes may be produced with dry pressing
however in such a process small
particles may agglomerate and lead to
poorer magnetic properties compared to
the wet pressing process direct
calcination and sintering without re
milling is possible as well but leads to
poor magnetic property
electromagnets are pre sintered as well
milled and pressed
however the centering takes place in a
specific atmosphere for instance one
with an oxygen shortage the chemical
composition and especially the structure
very strongly between the precursor and
de cinta docked to allow efficient
stacking of product in the furnace
during sintering and prevent parts
sticking together many manufacturers
separate we're using ceramic powder
separator sheets these sheets are
available in various materials such as
alumina zirconia and magnesia they are
also available in fine medium and coarse
particle sizes by matching the material
and particle size to the web being
sintered surface damage and
contamination can be reduced while
maximizing furnace loading uses ferrite
cores are used in electronic conductors
transformers and electromagnets where
the high electrical resistance of the
ferrite leads to very low eddy current
losses they are commonly seen as a lump
in a computer cable called a ferrite
bead which helps to prevent high
frequency electrical noise from exiting
or entering the equipment early computer
memory stored data in the residual
magnetic fields of hard ferrite cores
which were assembled in two arrays of
cool memory ferrite powders are used in
the coatings of magnetic recording tapes
one such type of material is iron oxide
ferrite particles are also used as a
component of radar absorbing materials
or coatings used in stealth aircraft and
in the absorption tiles lining the rooms
used for electromagnetic compatibility
measurements most common radio magnets
including those used in loudspeakers are
ferrite magnets ferrite magnets have
largely displaced alnico magnets in
these applications it is a common
magnetic material for electromagnetic
instrument pickups ferrite nanoparticles
exhibits superparamagnetic properties
see also ferromagnetic material
properties ferrite core
Frances external links international
magnetics association what are the bumps
at the end of computer cables sources mm
PA Oh 100 - Oh Oh standard
specifications for permanent magnet
materials meal dish Victor electronic
components selection and application
guidelines 1997 wiley ISBN 0-471-65653-4
teen - - bartlett bruce and others
practical recording techniques 2005
focal press ISBN