Ferromagnetic material: The basis of strong magnets

Ferromagnetic material describes substances that have particularly strong magnetic properties. They are the basis for most permanent magnets and electromagnets. In these materials, the magnetic moments of the atoms or molecules are aligned parallel to each other, resulting in maximum magnetisation. This property makes ferromagnetic materials essential for numerous industrial and technological applications.

How does ferromagnetism work?

In ferromagnetic materials, the atoms interact in such a way that their magnetic moments align in parallel due to the so-called interaction of exchange forces. This alignment strengthens the magnetic moment and leads to a strong, measurable magnetic field. This order remains even after the removal of an external magnetic field, resulting in permanent magnets.

Examples of ferromagnetic materials

• Iron (Fe): A widely used ferromagnetic material that is often used in electromagnets and permanent magnets.
• Nickel (Ni): Often used in alloys to improve corrosion resistance and magnetisation.
• Cobalt (Co): Known for its high temperature stability and use in high-performance magnets.
• Alloys: AlNiCo and neodymium-iron-boron (NdFeB) combine ferromagnetic elements to create powerful magnets.

Properties of ferromagnetic materials

• High magnetisation: Ferromagnetic materials have a strong magnetic moment and can be permanently magnetised.
• Hysteresis effect: The magnetisation remains even after an external magnetic field is removed.
• Curie temperature: Above this temperature, ferromagnetic materials lose their magnetic properties.
• Good electrical conductivity: Metals such as iron and nickel are also excellent electrical conductors.

Typical applications of ferromagnetic materials

Ferromagnetic materials are indispensable in many areas due to their strong magnetisation:

• Electric motors: Iron cores in motors strengthen the magnetic field and increase efficiency.
• Transformers: In transformers and inductors, ferromagnetic cores minimise energy losses.
• Permanent magnets: These materials are the basis for magnets in loudspeakers, electric motors and sensors.
• Memory media: Ferromagnetic layers used to be used in magnetic tapes and hard drives.

Interesting facts about ferromagnetic materials

Did you know that ferromagnetic materials are rare in nature? Only a few elements such as iron, nickel and cobalt are naturally ferromagnetic. However, the combination of these elements in alloys has revolutionised modern high-performance magnets, which are indispensable in wind turbines and electric vehicles.

Difference between ferro- and ferrimagnetic material

Ferrimagnetic material:
In ferrimagnetic materials, the magnetic moments of the atoms or ions are partially aligned in opposite directions. However, the strength of the opposing moments is different, so that a net magnetic moment remains.

Examples:

• Magnetite (Fe₃O₄)
• Barium ferrite
• Strontium ferrite

Typical properties:

• Incomplete alignment: The moments in different sublattices do not completely equalise, so a magnetic field is generated.
• Poor electrical conductor: Ferrimagnetic materials are often electrically insulating (e.g. ferrites).
• Temperature dependence: As with ferromagnets, magnetisation decreases with increasing temperature and disappears at the Curie temperature.

Use:

• Electronic components (ferrite cores)
• Permanent magnets
• Antennas

Ferromagnetic material:
In ferromagnetic materials, the magnetic moments of the atoms or ions align completely parallel to each other, resulting in strong magnetisation.

Examples:

• Iron (Fe)
• Nickel (Ni)
• Cobalt (Co)

Typical properties:

• Full alignment: All magnetic moments reinforce each other, resulting in maximum magnetisation.
• Electrical conductivity: Ferromagnetic metals are generally good conductors.
• High magnetisation: The magnetisation is stronger than with ferrimagnetic materials.

Use:

• Electromagnets
• Transformers
• Magnetic tapes

Most important difference

• Ferrimagnetic materials:
  Have opposite but different strength moments that create a net magnetic field.

• Ferromagnetic materials:
  All moments are aligned in parallel, which results in very strong magnetisation.