Question

What is meant by ferromagnetic substances?

Answer 1

Hint: The word ferromagnetism is derived from the word ‘ferrous’ which means iron. Iron was basically the first metal to show attractive properties to magnetic fields.

Complete answer:
The atoms in any solid possess a permanent magnetic dipole moment by virtue of electron spin and orbital magnetic moments. These magnetic dipoles are grouped in small volume inside a solid. Those small volume regions are called domains. Inside a domain, all dipole moments are oriented in a unique alignment giving a net magnetic moment to the domains. There are several domains of magnetic dipoles inside a solid. These domains are separated by domain boundaries or walls. Normally, domains are microscopic in size and have different magnetization orientation.
The magnitude of the magnetic field for the entire solid is the vector sum of magnetizations of all domains. For an unmagnetized specimen, the resultant magnetization of all domains is zero. But when subjected to an external magnetic field these domains’ magnetization orientation becomes same and thus producing a net magnetic moment inside the solids.
In some materials, the magnetization is lost after the removal of magnetic fields but ferromagnetic materials retain the magnetization even after the removal. They are strongly magnetized when exposed to a magnetic field. This property is generally exhibited by transition metals like Iron, Cobalt and Nickel etc.
Hence, the two suitable examples of ferromagnetic substances are Cobalt and Nickel.

Note:
There are other materials in which the magnetization is lost when the external magnetic field is removed. Examples of such materials are diamagnetic substances and paramagnetic substances.