Paramagnetism and temperature dependence: For a paramagnetic material, does magnetic susceptibility increase or decrease with increasing temperature?

Introduction / Context:
Paramagnetic materials contain atomic or ionic moments that tend to align with an applied magnetic field, increasing the material's magnetization. Thermal agitation counteracts this alignment. The classical Curie law captures how susceptibility varies with absolute temperature for many paramagnets.

Given Data / Assumptions:

• Material is paramagnetic (no spontaneous magnetization in zero field).
• Moderate temperature range where Curie or Curie–Weiss behavior holds.
• Weak applied field so linear susceptibility χ applies.

Concept / Approach:

Curie law states χ = C / T, where C is the Curie constant. Therefore, susceptibility decreases as temperature increases, approximately inversely proportional to T. In some materials with interactions, Curie–Weiss law applies: χ = C / (T − θ), but the inverse temperature relationship remains the essential trend away from ordering temperatures.

Step-by-Step Solution:

Verification / Alternative check:

Plotting 1/χ vs. T yields a straight line for many paramagnets, confirming inverse dependence.

Why Other Options Are Wrong:

• Temperature independence contradicts Curie behavior.
• Increase-then-decrease lacks basis for simple paramagnets outside critical regions.

Common Pitfalls:

• Confusing paramagnetism with ferromagnetism, where domain behavior dominates and χ can exhibit complex T-dependence near Curie temperature.

Final Answer:

False: susceptibility decreases with temperature (approximately inversely proportional to T)