2. MAGNETIC MATERIALS
• The materials which strongly attract apiece of iron are known
as magnetic materials or magnets.
• The magnetic property of a material arises due to the magnetic
moment or magnetic dipole of materials.
• Materials which are magnetised by the application of an
external magnetic field are known as magnetic materials.
3. MAGNETIC PROPERTIES OF MATERIALS
Magnetic Field:
The magnetic field is an imaginary
line of force around a magnet which enables
other ferromagnetic materials to get repelled
(or) attracted towards it.
The magnetic field lines are formed
due to various reasons like orbital movement
of electrons, current flower in a conductor etc.
4. MAGNETIC PROPERTIES OF MATERIALS
Properties of Magnetic Field Lines:
The magnetic field lines by convention enter through the south pole and
comes out from the north pole.
The magnetic field lines are strong near the poles of the magnet.
There is no chance of magnetic field lines intersecting with other.
More than closeness of the magnetic field lines, more strength of magnet.
5. MAGNETIC PROPERTIES OF MATERIALS
Magnetic Field Strength (H) :
Let us consider a current carrying
conductor coil has produced a magnetic field (H)
as shown in fig.
The magnetic field ‘H’ is given by,
Where, n=number of turns in coil, i = current in Amps , L= length of the coil in meters
6. MAGNETIC PROPERTIES OF MATERIALS
Magnetic Flux Density (B) :
when a substance is subjected to the magnetic field ‘H’ then the density of
the magnetic field lines that passes through the substances per square meter is
known as “Magnetic flux density (B)”, it is given by
Where μ is called the permeability and is defined as the degree to which a
substance gets magnetized.
7. Types of Magnetic Materials
• Paramagnetic Materials
• Diamagnetic materials
• Ferro magnetic materials
• Ferrimagnetism
• Anti ferromagnetism
8. Paramagnetic Materials
These materials are attracted by magnets and
when placed in magnetic field move from weaker to
stronger parts of the field.
Ex: Aluminium, Manganese, Platinum, Crown glass
The behavior of a paramagnetic material under the
influence of an external field is shown in fig.
9. Properties of Paramagnetic Materials
If a bar of paramagnetic material is suspended between the pole pieces of an
electromagnet it sets itself parallel to the lines of force.
When a bar of paramagnetic material is placed in a magnetic field the lines of
force tend to accumulate in it.
Paramagnetic susceptibility is inversely proportional to temperature.
10. diamagnetic Materials
Diamagnetic materials are those which are
repelled by magnets and when placed in magnetic field
move from stronger to weaker part of the field.
Ex: Bismuth, Copper, Phosphorous, Alcohol etc.
In the presence of a field, dipoles are
induced and aligned opposite to the field
direction as shown in Fig.
11. Properties of diamagnetic Materials
When a diamagnetic substance is placed in a magnetic field it sets itself at right
angles to the direction of lines of force.
When diamagnetic material is placed within a magnetic field the lines of force
tend to go away from the material.
They do not have a permanent dipoles moment.
The susceptibility of a diamagnetic material is negative.
The susceptibility is independent of temperature and external field.
12. ferromagnetic Materials
Ferromagnetic materials are attracted by the
magnets and can also be magnetized.
Ex: Iron, Nickel, Cobalt and their alloys
Mutual alignment of atomic Dipoles. even in
the absence of an external magnetic field.
coupling forces align the magnetic spins.
13. Properties of ferromagnetic Materials
The ferromagnetic substance shows the properties of the paramagnetic
substance to a much greater degree.
They have characteristic temperature, namely “ferromagnetic Curie
temperature”(𝜃𝑓) at this temp. these materials tend to loss its magnetic properties
Materials below 𝜃𝑓 behave as ferromagnetic materials and obey hysteretic
curve. A material behave as a paramagnetic when it is above 𝜃𝑓.
They possess permanent dipole moment.
14. ferrimagnetism
• A special case of antiferromagneticmaterials.
• The magnetic dipoles are antiparallel.
• However, their magnitudes are not equal.
• Hence, they produce a large magnetization even for a small applied
external field.
15. Properties of ferrimagnetic Materials
• The dipoles are antiparallel as shown in Fig. However, the
dipoles are not equal in magnitude.
• Net magnetization is larger even for a small
external field.
• The susceptibility is positive and vary large when the temperature is higher
than 𝑇𝑁,
𝜒 = 𝐶
𝑇±𝜃
• They behave as paramagnetic and ferromagnetic materials respectively
above and below Curie temperature.
16. Anti-ferromagnetism
The antiparallel alignment exists in material below a critical temperature
known as Neel temperature.
Ferrous Oxide
Manganese Oxide
Manganese Sulphite
Chromium Oxide
17. Properties
• The dipoles are aligned anti-parallel as shown in Fig.
• When the temperature increases, susceptibility increase
and reaches a maximum at a temperature known as Neel
temperature beyond which it decreases.
• The value of susceptibility is positive and is very small
when T is greater then the Neel temperature, 𝑇𝑁.
𝜒 = 𝐶
𝑇+𝜃
