Curie temperature of iron (ferromagnetic to paramagnetic transition) Approximate the Curie temperature for elemental iron, above which it loses ferromagnetism and becomes paramagnetic. Choose the closest value.

Introduction / Context:
The Curie temperature Tc marks the phase transition from ferromagnetic to paramagnetic behavior. Knowing Tc is essential in materials selection for magnets, transformers, and sensors where operating temperatures must remain well below Tc to maintain magnetic performance.

Given Data / Assumptions:

• Element: iron (Fe).
• We seek an approximate numerical value.
• Room temperature is far below iron’s Tc.

Concept / Approach:

Iron’s Curie temperature is approximately 1043 K (about 770°C). Above this temperature, thermal agitation disrupts long-range spin alignment, and the material behaves as a paramagnet. Therefore, “about 1000 K” is the closest rounded option commonly used in quick design estimates.

Step-by-Step Solution:

Verification / Alternative check:

Reference data for α-Fe report Tc between about 1040–1045 K depending on purity and measurement, validating the rounded choice.

Why Other Options Are Wrong:

20 K and -20°C are far too low; 100°C is still ferromagnetic; 300 K (room temperature) is below Tc, so iron remains ferromagnetic there.

Common Pitfalls:

Confusing Celsius and Kelvin scales or mixing iron with other ferromagnets that have different Curie temperatures (e.g., nickel ≈ 627 K).

Final Answer:

about 1000 K