This document discusses different types of magnetic materials: - Diamagnetic materials do not have a permanent magnetic moment and are weakly repelled by magnetic fields. Paramagnetic materials have a permanent magnetic moment and are weakly attracted to magnetic fields. Ferromagnetic materials spontaneously magnetize in the absence of an external field due to the parallel alignment of atomic dipoles. Antiferromagnetic and ferrimagnetic materials also have permanent magnetic moments but their dipoles align antiparallel, resulting in weaker magnetization. Each category of material exhibits distinct magnetic behaviors that depend on temperature and applied magnetic fields.

1. Magnetic Materials

2. 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. 3
Classification of Magnetic Materials
• Diamagnetic materials-no permanent magnetic
moment
• Paramagnetic, ferromagnetic, antiferromagnetic
and ferromagnetic materials-possess permanent
magnetic moment

4. 4
Diamagnetic Materials
In the presence of a field, dipoles are induced and aligned
opposite to the field direction Fig. 1.
Fig. 1.

5. 5
Properties of Diamagnetic Materials
• They do not have a permanent dipoles moment.
• Magnetic effects are very weak and hence, often masked by
other kind of magnetism.
• The megnetisation becomes zero on removal of the external
field.
• The susceptibility of a diamagnetic material is negative.
• The susceptibility is independent of temperature and external
field.

6. 6
• They repel the magnetic lines of force. The existence of this behavior in a
diamagnetic material is shown in Fig. 2.
𝐵 ≠ 0 𝐵 = 0
⟵Normal conductor
Diamagnetic Materials⟶
Fig. 2.
Properties of Diamagnetic Materials
Examples: Copper, Gold, Mercury, Silver and Zinc.

7. 7
Paramagnetic Materials
The behavior of a paramagnetic material under the
influence of an external field is shown in fig. 3.
Fig. 3.

8. 8
Properties of Paramagnetic Materials
• Paramagnetic material possess a permanent dipole moment.
• The attract the magnetic lines of force.
• The susceptibility is positive and depends on temperature:
𝜒 =
𝐶
𝑇
, Equation is known as the Curie law of paramagnetism.
• Paramagnetic susceptibility is inversely proportional to temperature.
Examples: Aluminum, chromium, sodium, titanium, zirconium, etc.

9. 9
Ferromagnetic Materials
Mutual alignment of atomic Dipoles. even in the absence of an
external magnetic field. coupling forces align the magnetic spins.
Fig. 4.

10. 10
Properties of Ferromagnetic Materials
• The magnetic dipoles are arranged parallel to each other. The spin
arrangement is shown in Fig. 5.
Fig. 5. Ferromagnetic materials-spin arrangement

11. 11 Properties of Ferromagnetic Materials
• They have characteristic temperature, namely, ferromagnetic Curie
temperature(𝜃𝑓). 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.
• The susceptibility of a ferromagnetic material is
𝜒 = 𝑐
𝑇−𝜃
, shown as Curie-Weiss law.
Examples: Iron, Cobalt, Nickel.

12. 12
Antiferromagnetic Materials
The antiparallel alignment exists in material below a critical temperature
known as Neel temperature.
Fig. 6.

13. 13
Properties of Antiferromagnetic Materials
• The dipoles are aligned anti-parallel as shown in Fig. 7.
• 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, 𝑇 𝑁.
𝜒 = 𝐶
𝑇+𝜃
Fig. 7.
Examples: ferrous oxide, manganese oxide,
manganese sulphite, chromium oxide, etc.

14. 14
Ferrimagnetic Materials
• A special case of antiferromagnetic materials.
• The magnetic dipoles are antiparallel.
• However, their magnitudes are not equal.
• Hence, they produce a large magnetisation even for a
small applied external field.

15. 15
Properties of Ferrimagnetic Materials
Fig. 8.
• The dipoles are antiparallel as shown in Fig. 8.
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 𝑇 𝑁,
𝜒 = 𝐶
𝑇±𝜃
• They behave as paramagnetic and ferromagnetic materials respectively
above and below Curie temperature.

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