Iron is a magnetic material because it contains unpaired electrons, which align in the presence of an external magnetic field.

The SI unit of magnetic field strength is Tesla (T), which is defined as one weber per square meter (Wb/m^2).

Hard steel is a permanent magnet because it retains its magnetization even after the external magnetic field is removed.

Demagnetization is the phenomenon of losing magnetic properties when heated above a certain temperature, known as the Curie temperature.

The relationship between magnetic field strength (H) and magnetic flux density (B) in a material is given by H = B/μ, where μ is the magnetic permeability of the material.

Diamagnetic materials have a negative magnetic susceptibility and repel magnetic fields. Copper is a diamagnetic material.

Magnetic hysteresis is the property of a material that opposes the change in its magnetization when an external magnetic field is applied.

Paramagnetic materials have a positive magnetic susceptibility and are weakly attracted to magnetic fields. Oxygen is a paramagnetic material.

Magnetic saturation is the point at which a material reaches its maximum magnetization and cannot be further magnetized.

Ferromagnetic materials have a strong positive magnetic susceptibility and are strongly attracted to magnetic fields. Iron is a ferromagnetic material.

Magnetic hysteresis is the phenomenon of a sudden change in the magnetization of a material when an external magnetic field is applied.

Antiferromagnetic materials have a negative magnetic susceptibility and their magnetic moments are arranged in an antiparallel fashion.

Magnetic remanence is the property of a material that describes its ability to store magnetic energy.

Ferrimagnetic materials have a positive magnetic susceptibility and their magnetic moments are arranged in a parallel and antiparallel fashion.

Magnetic hysteresis is the phenomenon of a sudden change in the magnetization of a material when an external magnetic field is removed.