Question

Above Curie temperature, ferromagnetic substances become ________
(a) Diamagnetic
(b) Paramagnetic
(c) Ferrimagnetic
(d) None of these

Answer 1

Hint: The magnetic moment of ferromagnetic substances weakens at higher temperature. They are weakly attracted by a magnetic field.

Complete step by step answer:
Let us first establish what the Curie temperature really means before moving onto its significance on the magnetism of substances.
> The Curie Point or Curie Temperature is the temperature above which the magnetic properties of certain substances change drastically. The material in which this change is the most noticed are ferromagnetic substances.
> The ferromagnetic substances are those who are strongly attracted by a magnetic field. The atomic arrangement in these solids favour this kind of behaviour. The metal ions are grouped together into domains, where all of them are aligned in a particular direction. The whole solid has many such domains that are randomly arranged which results into zero magnetic properties for the ferromagnetic material. But things change when an external magnetic field is applied. The domains rearrange themselves so as to align in the direction of the external magnetic field. Now the same substance becomes a powerful magnet. So powerful that, even if the external field is removed, the magnetic properties still stay with the solid. Ferromagnetic substances are used to make permanent magnets.
> At the Curie Point, these domains, which are the functional units of ferromagnetic substances, are unable to retain their forms and therefore disintegrate. Hence, losing their ferromagnetism, these solids now turn paramagnetic.

Therefore, the answer to the above question is option (b).

Note: The Curie Point is defined for any substance which shows magnetic property. Although the names for this particular temperature are different for different types of magnetic substance, the concept remains the same.
Both paramagnetic and ferromagnetic substances are attracted by a magnetic field, but they have a huge difference between them. The former is weakly attracted while the latter is attracted very strongly.