Here's why:
* Curie temperature refers to the temperature above which a ferromagnetic or ferrimagnetic material loses its permanent magnetic properties and becomes paramagnetic.
* Copper sulfide (CuS) is not a ferromagnetic or ferrimagnetic material. It's an antiferromagnetic material.
Antiferromagnetic materials have magnetic moments that align in opposing directions, resulting in a net magnetic moment of zero. This means they don't exhibit the same kind of permanent magnetism as ferromagnetic materials and therefore don't have a Curie temperature.
Instead of a Curie temperature, antiferromagnetic materials have a Néel temperature, which is the temperature above which the material loses its antiferromagnetic properties and becomes paramagnetic. However, the Néel temperature of CuS is not well-defined and varies significantly depending on the specific form of CuS and the experimental conditions.
