Diamagnetic, Paramagnetic, Ferromagnetic Material: Definition, Types and Difference

Magnetism is an essential part of our everyday world — it powers electric motors, runs transformers, stores data, and even helps doctors see inside the human body through MRI scans. Different materials react differently when exposed to a magnetic field, depending on how their atoms and electrons are arranged.Based on their response, materials are grouped into three main types: diamagnetic, paramagnetic, and ferromagnetic. Diamagnetic materials are slightly pushed away by a magnetic field, paramagnetic materials are gently pulled toward it, and ferromagnetic materials show a strong attraction — in fact, they can even become permanent magnets.

1.0Definition of Magnetic Materials

Magnetic materials are substances that react to an external magnetic field by getting magnetized. How they behave depends on how the tiny magnetic moments of their atoms or ions are aligned. Based on this response, materials are generally classified into three types: diamagnetic, paramagnetic, and ferromagnetic.

2.0Types of Magnetic Materials

Diamagnetic Materials

Diamagnetic materials are substances that are weakly repelled by a magnetic field. This happens because the magnetic moments of their atoms or molecules oppose the applied magnetic field.

• Magnetic susceptibility $\chi$ is negative.
• They do not retain magnetism once the external field is removed.
• The effect is very weak and independent of temperature.
• Examples: Copper (Cu), Bismuth (Bi), Silver (Ag), Gold (Au).
  Diamagnetic materials are non-magnetic in nature, and their atoms create tiny currents that oppose any applied magnetic field, causing a slight repulsion.

Paramagnetic Materials

Paramagnetic materials are substances that are weakly attracted by a magnetic field. This occurs because they have unpaired electrons whose magnetic moments tend to align with the applied field.

• Magnetic susceptibility $\chi$ is small and positive.
• They do not retain magnetism when the external field is removed.
• The magnetic effect increases at lower temperatures and follows Curie’s Law:

$\chi =\frac{C}{T}$
Where C = Curie Constant and T is Absolute Temperature.

Examples: Aluminum (Al), Platinum (Pt), Chromium (Cr), Manganese (Mn).

Ferromagnetic Materials

Ferromagnetic materials are substances that are strongly attracted by a magnetic field and can retain their magnetism even after the external field is removed, forming permanent magnets.

• Magnetic susceptibility $\chi$ is very large and positive.
• They exhibit spontaneous alignment of magnetic moments in regions called magnetic domains.
• Show hysteresis, meaning the magnetization lags behind changes in the applied field.
• Lose their ferromagnetism above a certain temperature called the Curie temperature ($T_C$).
• Examples: Iron (Fe), Nickel (Ni), Cobalt (Co), Steel.
  Ferromagnetic materials are strongly magnetic and are the basis of permanent magnets and many technological applications like transformers, motors, and memory devices.

In ferromagnetic materials, small regions known as magnetic domains naturally form when groups of atomic magnetic moments align in the same direction because of a force called the exchange interaction. Instead of the entire material acting as one large magnet, it breaks up into many smaller domains to lower its overall magnetic energy. In an unmagnetized state, these domains point in random directions, so their magnetic effects cancel each other out. However, when an external magnetic field is applied, the domains that point in the same direction as the field grow larger, making the material strongly magnetized.

Difference Between Diamagnetic, Paramagnetic And Ferromagnetic Material

On the basis of magnetic properties of the materials [as magnetization intensity I, Susceptibility ${\chi }_m$ and relative permeability ${\mu }_r$], Faraday divided these materials into three classes based on the observation of how materials respond to an external magnetizing field H.

Classification of Magnetic Materials

Properties	Diamagnetic	Paramagnetic	Ferromagnetic
I	Small, negative	Small, positive	Very large, positive
${\chi }_m$	Small, negative	Small, positive	Very Large, positive
${\mu }_r$	$1>{\mu }_r>0$	$2>{\mu }_r>1$	${\mu }_r\gg 1$
I − H curve	I→ Small, negative varies linearly with field	I→ Small, positive, varies linearly with field	I→ very large, positive varies non-linearly with field
Variation of m with Temp	${\chi }_m\to$ small, negative & temperature Independent ${\chi }_m\propto T^0$	${\chi }_m\to$ small, positive & varies inversely with temp. Curie law ${\chi }_m\propto \frac{1}{T}$	${\chi }_m\to$ very large, positive & temp. dependent Curie Weiss law (for$T>T_C){\chi }_m\propto \frac{1}{T-T_C}$
Degree of magnetization
Behavior in non-uniform magnetizing field
Magnetic moment of single atom	Atoms do not have any permanent magnetic moment	toms have permanent magnetic moment which are randomly oriented. (i.e. in absence of external magnetic field the magnetic moment of whole material is zero)	Atoms have permanent magnetic moment which are organised in domains.
When rod of material is suspended between poles magnet.	It becomes perpendicular to the direction of external magnetic field.	If there is strong magnetic field in between the poles then rod becomes parallel to the magnetic field.	Weak magnetic field between magnetic poles can made rod parallel to field direction.
Magnetic moment of substance in presence of external magnetic field	Value M is very less and opposite to H.	Value M is low but in direction of H.	M is very high and in direction of H.
Examples	Bi, Cu, Ag, Pb,$H_{2}O$, Hg,$H_2$, He, Ne, Au, Zn, Sb, NaCl, Diamond. (May be found in solid, liquid or gas).	Na, K, Mg, Mn, Sn,Pt, Al, O2(May be found in solid, liquid or gas.)	Fe, Co, Ni all their alloys,$F{e}_3{O}_4$ Gd, Alnico, etc.(Normally found only in solids) (crystalline solids)

Note: Above Curie temperature, ferromagnetic materials lose their permanent magnetic properties and behave as paramagnetic materials.