Magnetic Properties
Introduction
• Magnetism arises from the Magnetic Moment or
Magnetic dipole of Magnetic Materials.
• When the electrons re...
Magnetic Induction or Magnetic flux Density
The Magnetic induction in any material is the number
of lines of magnetic forc...
Permeability: ( µ )
The Magnetic induction B is proportional to the
applied Magnetic field intensity H.
H
B
HB
HB
=
=
µ
µ
...
Relative permeability µr
The ratio of permeability of medium to
the permeability of free space is called
relative permeabi...
Magnetization
•Magnetization refers to the process of
converting a non-magnetic material into a
Magnetic material.
•The in...
mr
r
r
r
r
r
r
H
M
H
MH
MH
B
H
B
MH
B
MHB
MHB
HHB
HHHB
HB
HB
HB
χµ
µ
µ
µ
µ
µ
µ
µ
µµ
µµµ
µµµµ
µµ
µ
α
+=
+=
+
=
+
→=
+
=
+=
...
Origin of Magnetic Moment
The Magnetic moment in a material originates from the
orbital motion and spinning motion of elec...
Consider an atom & each electron in
that, orbiting around the nucleus
produces a loop current
i = q / t
i = q f
Where f is...
L
m
q
mvr
m
q
qvr
r
vq
r
q
r
f
q
r
qfr
t
q
r
lm
lm
lm
lm
lm
lm
lm
lm
.
2
.
2
2
)
2
)((
)
2
)((
)2
2
)((
))((
))((
2
2
2
2
...
224
1027408.9
4
),.(.,
)1(.
)1(.
4
2
)1(.
2
.
2
2
)1(
2
mA
m
qh
magnatonBhorwhere
ll
ll
m
qh
h
ll
m
q
L
m
q
h
llmvrL
lh
mv...
Classification of Magnetic
Materials
1. Dia
2. Para
3. Ferro
4. Anti Ferro
5. Ferri Magnetic materials.
Hysteresis
The striking property of Ferro Magnetic
materials is the relation between
Magnetization and the strength of
Mag...
P
Q
R
S
H
M
Saturation
Magnetization
Residual
Magnetization
Coercivity
Ferro Magnetic Material
Hs
-Hs
oHc
Ms
Mr
-Ms
• If we start with no Magnetized specimen
(M= 0) with the increasing values of
magnetizing field H.
• The Magnetization of...
• When we increase Magnetic field H
there is no further increment in Magnetic
moment.
• When we decrease Magnetic field H ...
• Further if we increase the Magnetic field
from zero to negative values, the
Magnetization of material becomes zero
at a ...
• On reversing the polarities of Magnetic
field and increasing its strength the
Magnetization slowly decreases first to
re...
Hard Magnetic Materials
• Hard magnetic materials have large
hysteresis loss due to large hysteresis
loop area.
• The Coer...
Soft Magnetic Materials
• Soft Magnetic materials have low
hysteresis loss due to small hysteresis loop
area.
• The coerci...
Superconductivity
• Certain metals and alloys exhibit
almost zero resistivity ( infinite
conductivity ) when they are cool...
Meissner Effect
When a weak Magnetic field is applied to a
superconducting specimen at a temperature Tc ,
the magnetic flu...
PER FECT DIAMAGNATIC MATIRIAL OR SUPER CONDUCTING MATERIAL
MAGANTIC FIELD
B = 0
1
1
0
)(0
0
)(
)(
0
0
0
−=
−=
−=
=+
+=
=
+...
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MAGNETIC PROPERTIES

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MAGNETIC PROPERTIES

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MAGNETIC PROPERTIES

  1. 1. Magnetic Properties
  2. 2. Introduction • Magnetism arises from the Magnetic Moment or Magnetic dipole of Magnetic Materials. • When the electrons revolves around the nucleus Orbital magnetic moment arises, similarly when the electron spins, spin Magnetic moment arises. • The permanent Magnetic Moments can arise due to the 1.The orbital magnetic moment of the electrons 2.The spin magnetic moment of the electrons, and 3.The spin magnetic moment of the nucleus.
  3. 3. Magnetic Induction or Magnetic flux Density The Magnetic induction in any material is the number of lines of magnetic force passing through unit area perpendicularly. Units: Wb/m2 or Tesla. Magnetic field intensity (H) The Magnetic field intensity at any point in the magnetic field is the force experienced by an unit north pole placed at that point. Units : A/m
  4. 4. Permeability: ( µ ) The Magnetic induction B is proportional to the applied Magnetic field intensity H. H B HB HB = = µ µ α Where µ permeability of a medium
  5. 5. Relative permeability µr The ratio of permeability of medium to the permeability of free space is called relative permeability µr of the solid. 00 0 B B H B H B r r == = µ µ µ µ
  6. 6. Magnetization •Magnetization refers to the process of converting a non-magnetic material into a Magnetic material. •The intensity of Magnetization is directly related to the applied field H. H M HM HM m m = = χ χ α litysusceptibimagnetic
  7. 7. mr r r r r r r H M H MH MH B H B MH B MHB MHB HHB HHHB HB HB HB χµ µ µ µ µ µ µ µ µµ µµµ µµµµ µµ µ α += += + = + →= + = += += −+= −+= = = 1 1 )( typermeabilirelative )( )( ionmagnetizattheisMWhere )1( 0 0 0 00 00 000 0
  8. 8. Origin of Magnetic Moment The Magnetic moment in a material originates from the orbital motion and spinning motion of electrons in an atom. e µlm
  9. 9. Consider an atom & each electron in that, orbiting around the nucleus produces a loop current i = q / t i = q f Where f is a frequency of electron.. If L is the angular momentum of electron, the Magnetic moment of the electron µ = (Area of loop) x (Current)
  10. 10. L m q mvr m q qvr r vq r q r f q r qfr t q r lm lm lm lm lm lm lm lm . 2 . 2 2 ) 2 )(( ) 2 )(( )2 2 )(( ))(( ))(( 2 2 2 2 2 = = = ×= ×= ×= = = µ µ µ π πµ ω π πµ π π πµ πµ πµ Where L is a Angular Momentum of electron
  11. 11. 224 1027408.9 4 ),.(., )1(. )1(. 4 2 )1(. 2 . 2 2 )1( 2 mA m qh magnatonBhorwhere ll ll m qh h ll m q L m q h llmvrL lh mvrL B Blm lm lm lm −×→= += += += = +== == − π µ µµ π µ π µ µ π π
  12. 12. Classification of Magnetic Materials 1. Dia 2. Para 3. Ferro 4. Anti Ferro 5. Ferri Magnetic materials.
  13. 13. Hysteresis The striking property of Ferro Magnetic materials is the relation between Magnetization and the strength of Magnetic field. This property is called Hysteresis.
  14. 14. P Q R S H M Saturation Magnetization Residual Magnetization Coercivity Ferro Magnetic Material Hs -Hs oHc Ms Mr -Ms
  15. 15. • If we start with no Magnetized specimen (M= 0) with the increasing values of magnetizing field H. • The Magnetization of the specimen increases from zero to higher values and attains its maximum value at a point P, at this point the Magnetization referred as Saturation Magnetization..
  16. 16. • When we increase Magnetic field H there is no further increment in Magnetic moment. • When we decrease Magnetic field H to Zero, the Magnetization M attains point Q. • At this point Magnetization referred as residual Magnetization Mr.
  17. 17. • Further if we increase the Magnetic field from zero to negative values, the Magnetization of material becomes zero at a point R, at that point the Magnetic field Hc is referred as Coercivity of the specimen. • If we increase Magnetic field H in reverse direction Magnetization of material reaches its peak value at a points S.
  18. 18. • On reversing the polarities of Magnetic field and increasing its strength the Magnetization slowly decreases first to residual value then to zero and finally increases to saturation state and touches the original saturation curve. • The area of loop indicates the amount of energy wasted in one cycle of operation.
  19. 19. Hard Magnetic Materials • Hard magnetic materials have large hysteresis loss due to large hysteresis loop area. • The Coercivity and retentivity are large hence these materials cannot be easily magnetized and demagnetized. • These materials have small values of permeability and susceptibility. • These are used to make permanent magnets. Ex. Alnico alloy
  20. 20. Soft Magnetic Materials • Soft Magnetic materials have low hysteresis loss due to small hysteresis loop area. • The coercivity and retentivity are small, hence these materials can be easily magnetized and demagnetized. • These materials have large values of permeability and susceptibility. • These are used to make electromagnets. Ex: Iron silicon alloys, Ferrous nickel alloy
  21. 21. Superconductivity • Certain metals and alloys exhibit almost zero resistivity ( infinite conductivity ) when they are cooled to sufficiently low temperatures. This phenomenon is called Superconductivity.
  22. 22. Meissner Effect When a weak Magnetic field is applied to a superconducting specimen at a temperature Tc , the magnetic flux lines are expelled & the specimen acts as an ideal Dia magnet. This effect is called Meissner effect. cTT 
  23. 23. PER FECT DIAMAGNATIC MATIRIAL OR SUPER CONDUCTING MATERIAL MAGANTIC FIELD B = 0 1 1 0 )(0 0 )( )( 0 0 0 −= −= −= =+ += = += += χ µ µ µ H M MH MH MH B MHB MHB cTT 
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