Question

Curie temperature is the temperature at which:

• A. Ferromagnetic $\rightarrow$ Paramagnetic
• B. Paramagnetic $\rightarrow$ Diamagnetic
• C. Solid $\rightarrow$ Liquid
• D. Magnetic $\rightarrow$ Non-magnetic

Hint:

For Iron (Fe), the Curie temperature is approximately $770^\circ\text{C}$ ($1043\text{ K}$).
Above this temperature, iron loses its permanent magnetic properties and behaves paramagnetically.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The question asks for the definition of the Curie temperature ($T_C$) and the magnetic phase transition that occurs at this point.

Step 2: Key Formula or Approach:
The magnetic behavior of a material is highly dependent on temperature.
The susceptibility of a material above its Curie temperature follows the Curie-Weiss Law:
\[ \chi = \frac{C}{T - \theta} \]
where $T_C$ represents the transition threshold.

Step 3: Detailed Explanation:

• Below the Curie temperature, a ferromagnetic material possesses spontaneous magnetization because exchange interactions keep adjacent atomic magnetic moments aligned parallel to one another within magnetic domains.

• As the temperature increases, thermal energy increases, causing the atoms to vibrate more vigorously.

• This thermal agitation disrupts the orderly alignment of the magnetic dipoles.

• At the Curie temperature ($T_C$), the thermal energy becomes strong enough to completely overcome the exchange coupling.

• Above this critical temperature, the magnetic dipoles become randomly oriented in the absence of an external field, transitioning the material from a ferromagnetic state to a paramagnetic state.

Step 4: Final Answer:
The Curie temperature is the temperature at which a ferromagnetic material transitions into a paramagnetic material.