Question

What is the effect of temperature on magnetic susceptibility of ferromagnetic materials?

• A. increases with increasing temperature.
• B. remains unchanged with increasing temperature.
• C. decreases with increasing temperature.
• D. Sometimes increases and sometimes decreases depending on the environment.

Hint:

Think of temperature as a randomizing force for magnetism. For ordered magnetic states like ferromagnetism, increasing temperature always leads to more disorder, thus reducing the magnetic properties like susceptibility and spontaneous magnetization.

Answer 1

The Correct Option is C

Step 1: Concept Overview:
Ferromagnetism arises from strong alignment of atomic magnetic moments due to quantum mechanical exchange. Thermal energy opposes this alignment. Magnetic susceptibility (\(\chi\)) quantifies a material's magnetization in a magnetic field.
Step 2: In-Depth Analysis:
As temperature rises in a ferromagnetic material, increased atomic vibration disrupts the magnetic domain ordering, counteracting exchange forces. This reduces overall magnetization and, consequently, magnetic susceptibility.
This effect intensifies near the Curie temperature (\(T_C\)). At \(T_C\), thermal energy overcomes exchange forces, causing a ferromagnetic-to-paramagnetic phase transition. Above \(T_C\), the material becomes paramagnetic, and susceptibility decreases with temperature according to the Curie-Weiss law: \(\chi = C/(T - T_C)\).
Step 3: Conclusion:
In summary, the magnetic susceptibility of a ferromagnetic material consistently diminishes with increasing temperature.