Definition:

Diamagnetic materials are weakly repelled by a magnetic field and have no permanent magnetic moment.

Key Points:

• No unpaired electrons → net magnetic moment = 0

• Magnetization (MMM) is opposite to applied field HHH

• Magnetic susceptibility (χ\chiχ) is negative

χ<0\chi < 0χ<0

Examples:

• Copper (Cu), Bismuth (Bi), Water (H₂O), Gold (Au)

Behavior in Magnetic Field:

• Slightly repelled

• Cannot retain magnetization

Diagram:

🔹 2️⃣ Paramagnetic Materials

✅ Definition:

Paramagnetic materials are weakly attracted by a magnetic field and do not retain magnetization.

Key Points:

• Some unpaired electrons → small net magnetic moment

• Magnetization (MMM) aligns with applied field HHH

• Magnetic susceptibility (χ\chiχ) is positive

χ>0\chi > 0χ>0

Examples:

• Aluminium (Al), Oxygen (O₂), Magnesium (Mg)

Behavior in Magnetic Field:

• Weak attraction

• Cannot retain magnetization once field is removed

Diagram:

🔹 3️⃣ Ferromagnetic Materials

✅ Definition:

Ferromagnetic materials are strongly attracted by a magnetic field and can retain magnetization.

Key Points:

• Many unpaired electrons → strong net magnetic moment

• Domains exist (regions where magnetic moments are aligned)

• Magnetic susceptibility (χ\chiχ) is very large and positive

χ≫1\chi \gg 1χ≫1

Examples:

• Iron (Fe), Cobalt (Co), Nickel (Ni)

Behavior in Magnetic Field:

• Strong attraction

• Can become permanent magnets

🔹 Hysteresis Loop (Ferromagnetic Behavior)

Definition:

A hysteresis loop shows how magnetization MMM lags behind the applied magnetic field HHH.

Key Features:

1. Saturation Magnetization (MsM_sMs)

   • Maximum magnetization achieved in strong field

2. Retentivity (MrM_rMr)

   • Magnetization left when H=0H = 0H=0

3. Coercivity (HcH_cHc)

   • Field required to reduce M=0M = 0M=0

4. Loop Shape

   • Shows energy loss in magnetic materials → important in transformers

Diagram (simplified):

• Area inside the loop = energy loss (hysteresis loss)

🔹 Quick Comparison Table