Engineering magnetic materials.

1. Magnetic materials

2. 1. The orbital motion of electrons -orbital magnetic
moment(magnitude is small)

3. Spin motion of the electrons -spin magnetic
moment.

4. • To the presence or absence of the permanent magnetic
dipoles.

5. • The orbital motion of electron revolving about a
nucleus is equivalent to a tiny current loop. This
produces a magnetic field perpendicular to the
plane of the orbit

6. • Energy states – it will form a pair with opposite spins.
• Resultant spin magnetic moment is zero.
• Don’t have permanent magnetic moments ex. Diamagnetic
materials (gold, germanium, silicon)
Energy

7. • Those materials having unpaired electrons.
• Spin magnetic moment of these unpaired electrons
interact adjacent atoms.
• It has enormous permanent spin magnetic moment.
Classification of magnetic
materials
Not having
permanent
magnet
moment
Dia magnetic material
Having permanent
magnetic moment
1.Para magnetic
2.Ferromagnetic
3.Ferrri magnetic
materials

8. diamagnetism
• The atoms in Diamagnetic material do not
possess permanent magnetic moment.
• It is placed in M.F , the electrons tend to
counteract the external M.F. The atoms acquire
an induced magnetic moment.
H =0
Atoms
possess zero
magnetic
moment

9. • The material magnetized.
• The direction of the induced dipole moment is
opposite (due to applied magnetic field )
• The material gets very weakly repelled in the
M.F - diamagnetism
Ho is applied ,
atoms acquire an
induced
magnetic
moment

10. • Strength of the induced magnetic moment is
proportional to the Ho
• Hence magnetisation of the material varies
directly with strength of the Ho
• When Ho is removed the magnetization is
vanished.

11. Langevin’s theroy of damagnetism
• Materials exhibit diamagnetism due to the
orbital motion of an electron and produce a –
ve susceptibility.
χm =μind/H = -e2
r0
2
µoN/6m
μind-inducedmagneticmoment
e=chargeofanalectron
r0 radiusofatom
µo permeability in free space.
N – number of atoms per unit volume, m- mass of the electron

12. conclusions
is independent of temperature
is negative
is proportional to the N

13. properties
• They repel the magnetic lines of force
• I is –ve and independent of temperature and
Ho ( applied M.F)
• Ppermeability is less than 1
• There is no permanent dipole moment -weak
magnets.
• When temperature is less than critical
temperature diamagnetic become normal
material.

14. Absence of external magnetic field those material
(atom or molecule) possesses permanent magnetic
moment
1. Magnetic moments are randomly
oriented
2. Net magnetic moment zero and
magnetization is zero.
Paramagnetic materials

15. Field is applied
Magnetic dipoles tend to align themselves in the
direction of the magnetic field.
The materials becomes magnetized.

16. • High temperature is leading to decrease in
magnetization.
susceptibility is inversely temperature.
• susceptibility = C/T (Curie law of
paramagnetism )
• C is a constant – curie constant.

17. Langevin’s theory of paramagnetism
• χ, = µ2
m µoN/ 3KT
N- Number of molecules per unit volume
µo -permeabillity in free space
µ2
m magnetic dipole moment of atom
k-Boltzmann’s constant
T-temperasure
χ, =C/T where C=µ2
m µoN/ 3K (curie’s constant)

18. properties
1. The magnetic lines of force pass through the material.
2. Magnetic susceptibility is +ve . χ, =C/T –θ (Curie-weiss
law) here, C-curie constnat,T-absolute temperature,
θ- Curie temperature.
3. Permeability is greater than one.
4. They possess permanent dipole moment
5. When the temperature is less than curie
temperature, paramagnetic materials becomes
diamagnetic material. ( CuSO4 , platinum , nickel
sulphate ,etc.)
6. Spin alignment is shown

19. Ferromagnetism
• These materials show the spontaneous
magnetization.
• Absence of external field, the magnetic
moments align themselves parallel to each
other and give rise to magnetic field.
• When field is applied , magnetic moments
reorient itself along the direction of the
magnetic field and they become very strong
magnets.

20. Properties
• Science some magnetisation is already
existing in these materials, all the magnetic
lines fore passes through it. (strongly
attracted )
• They have permanent dipole moment.
• They act as strong magnets.
• the exhibit magnetisation even in the
absence of external field. This property is
called spontaneous magnetisation

21. • Susceptibility is +ve and high.
• When the temperature is greater than curie
temperature, ferromagnetic material
becomes paramagnetic materials.
• Permeability is very much greater than 1.
• Dipole alignment is as shown.
• They exhibit hysteresis curve.
• χ, =C/T –θ (for T> θ , para
T< θ, ferro
Ex. Ni, co, Fe, etc.