What are ferromagnetic materials and their properties?

Ferromagnetic materials are substances that can be magnetised and are strongly attracted to magnets.

Ferromagnetic materials are a unique class of materials that respond to magnetic fields in a way that no other materials do. They are the only materials that can become magnets themselves when exposed to a magnetic field. This is due to the alignment of unpaired electrons in their atoms, which creates a net magnetic moment.

The most common examples of ferromagnetic materials are iron, nickel, cobalt, and their alloys. Gadolinium and dysprosium are also ferromagnetic, but only at low temperatures. These materials are used in a wide range of applications, from hard drives to transformers and electric motors.

One of the key properties of ferromagnetic materials is their ability to retain their magnetisation, a property known as hysteresis. This means that once a ferromagnetic material has been magnetised, it will stay magnetised even when the external magnetic field is removed. This property is crucial for the functioning of devices like hard drives, which rely on the material's ability to maintain a magnetic field to store information.

Another important property of ferromagnetic materials is their high permeability to magnetic fields. This means that they can concentrate magnetic field lines, which makes them ideal for use in transformers and inductors.

However, ferromagnetic materials also have a saturation point, beyond which they cannot be further magnetised. This is known as the material's saturation magnetisation. If a ferromagnetic material is exposed to a magnetic field that is too strong, it can become permanently magnetised, a process known as magnetic saturation.

In addition, ferromagnetic materials can also exhibit a phenomenon known as magnetic domains. These are regions within the material where the magnetic moments of the atoms are aligned with each other. When a ferromagnetic material is magnetised, these domains align with the direction of the magnetic field.