Iron single crystal photomicrographs
magnetic domains change shape as a
magnetic field (H) is applied.
domains favorably oriented with the field
grow at the expense of the unfavorably
oriented domains.
Magnetic Properties
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Magnetic - Nanotechnology - Lecture Slides, Slides of Nanotechnology
Mechanical Applications, Molecular Separation, Nano Solar Cells, Nanocatalysts, Nanoparticles in Medicine, Agriculture and Genomics, Nanotoxicology, Nanowire Photonics, NDR Molecular, Zinc Oxide Nanowire and many others topics are part of this course. Key points in this lecture are: Magnetic, Crystal Photomicrographs, Magnetic Field, Magnetic Dipoles, Magnetic Flux Density, Magnetic Field Strength, Diamagnetic Material, Diamagnetism and Paramagnetism, Paramagnetic Material, Ferromagnetism
Typology: Slides
2012/2013
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Iron single crystal photomicrographsmagnetic domains change shape as amagnetic field (
H) is applied.
Magnetic Properties^ domains favorably oriented with the fieldgrow at the expense of the unfavorablyoriented domains.
c18f
Magnetic field lines of force around a current loop and a bar magnet.
18.2 Basic ConceptsMagnetic forces appear when moving chargesForces can be represented by imaginary lines grouped as fields
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Magnetic Field Vectors
magnetic field strength (H) &
magnetic flux density (B)
=
M
H
B
r^
=
H
=
M
m
magnetization
magnetic susceptibility
1
-
=
r
m
relative permeability^
H
=
B
H
= B
Magnetic flux density
l NI = H
Magnetic field strength
Bohr magneton (
)B
Most fundamental magnetic moment B^
= ±9.27x
A-m
(^2)
Origins of Magnetic Moments:Responds to quantum mechanics lawsTwo main contributions: (
a) an
orbiting electron and (
b) electron spin
The spin is anintrinsicproperty of theelectron and itis not due to itsrotation
c18f
The flux density
B versus the magnetic
field
strength
H for diamagnetic and paramagnetic
B^^ materials.
=
H
M
=
H
m
H
=
0
(1 +
m
)
c18f
ANTIFERROMAGNETISM Antiparallel alignment of spinmagnetic moments forantiferromagnetic manganeseoxide (MnO)At low TAbove the Neel temperature theybecome paramagnetic
Parent materials, La
CuO 2
, and YBa 4
Cu 2
O 3
demonstrated that the CuO
2
planes exhibit
antiferromagnetic order.This work initiated a continuing explorationof magnetic excitations in copper-oxidesuperconductors, crucial to the mechanismof high-temperature superconductivity.
1986: superconductivitydiscovered in layeredcompound La
2-x
Ba
CuOx
4
with a transition T muchhigher than expected.Little was known aboutcopper oxides
18.5 Antiferromagnetism & Ferrimagnetism
FERRIMAGNETISM spin magnetic momentconfiguration for Fe
2+
and Fe
3+
ions
in Fe
O 3
. Above the Curie 4
temperature becomesparamagnetic
- c18tf
- 18tf
- In our textbook 2.22, 1.72, 0.
18.6 The Influence of Temperature on magnetic Behavior^ T
: Curie temperature (ferromagnetic, ferrimagnetic)C T
: Neel temperature (antiferromagnetic)N material become paramagnetic
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B versus H ferromagnetic orferrimagnetic materialinitially unmagnetizedDomain configurationsduring several stages ofmagnetizationSaturation flux density,
B
s
Magnetization, M
,s^
initial
permeability
i
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Magnetic flux densityversus magnetic fieldstrength ferromagnetic materialsubjected to forward andreverse saturations (
S & S’).
hysteresis loop (red)initial magnetization (blue)remanence,
B
r
coercive force,
H
c
Temperature dependence of the electrical resistivityfor normally conducting andsuperconducting materials in thevicinity of 0 K.
18.12 Superconductivity
c18f
Critical temperature, current density, and magneticfield boundary separatingsuperconducting and normalconducting states (schematic).