Magnetism

Magnetism: A Magnetic Journey Through Time and Science

Imagine a world where invisible forces can pull or push objects across vast distances – that’s magnetism! How does this mysterious force work, and what makes some materials more magnetic than others?

The Basics of Magnetism

Magnetism is the class of physical attributes that occur through magnetic fields. These fields allow objects to attract or repel each other. It’s one aspect of electromagnetism, along with electric currents. Ferromagnetic materials are strongly attracted by magnetic fields and can be magnetized to produce permanent magnets.

History and Early Discoveries

Magnetism has been studied throughout history, with early mentions dating back to ancient Greece and China. Aristotle attributed an early scientific discussion of magnetism to Thales of Miletus, while the ancient Indian text Sushruta Samhita describes using magnetite to remove arrows from a person’s body.

Key Figures in Magnetism

In the Middle Ages, scientists such as Peter Peregrinus de Maricourt and Leonardo Garzoni wrote extensively on magnetic phenomena. William Gilbert published his groundbreaking work De Magnete in 1600, describing the properties of magnets and their effects on other materials.

The Birth of Electromagnetism

In 1819, Hans Christian Ørsted discovered that an electric current could create a magnetic field. This landmark experiment is known as Ørsted’s Experiment. Jean-Baptiste Biot and Félix Savart came up with the Biot–Savart law in 1820, giving an equation for the magnetic field from a current-carrying wire.

Maxwell’s Unification

From around 1861, James Clerk Maxwell synthesized and expanded many of these insights into Maxwell’s equations. These equations unified electricity, magnetism, and optics into the field of electromagnetism. The magnetic properties of materials are mainly due to the magnetic moments of their atoms’ orbiting electrons.

Magnetic Behavior in Materials

The magnetic behavior of a material depends on its structure, particularly its electron configuration, and also on temperature. At high temperatures, random thermal motion makes it more difficult for the electrons to maintain alignment. Depending on the direction of electron orbiting around a nucleus, this force may increase or decrease centripetal force and orbital magnetic moments according to Lenz’s law.

Types of Magnetism

Paramagnetic materials have unpaired electrons that align with an external magnetic field, causing reinforcement. Ferromagnetic substances also have unpaired electrons but with a tendency for their magnetic moments to orient parallel to each other, leading to spontaneous alignment even in the absence of an applied field.

Magnetic Domains

Ferromagnetic materials form magnetic domains where aligned magnetic moments behave like tiny permanent magnets. These domains can grow or shrink when exposed to a magnetic field. Antiferromagnetism is characterized by neighboring valence electrons’ intrinsic magnetic moments pointing in opposite directions, resulting in no net magnetic moment.

Electromagnets and Special Relativity

Magnetic dipoles, such as magnets, have a ‘South pole’ and a ‘North pole,’ which interact with other magnetic fields. The Earth’s North Magnetic Pole is physically a south pole, attracting north poles of compasses. A magnetic field contains energy and physical systems move towards lower-energy configurations.

Theoretical Models

Magnetism can be fully explained only using quantum theory. Walter Heitler and Fritz London developed a successful model in 1927, which derived how hydrogen molecules are formed from hydrogen atoms. According to the Heitler–London theory, so-called two-body molecular σ-orbitals are formed.

Conclusion

Magnetism is not just about attracting and repelling; it’s a complex interplay of electric currents, electron configurations, and temperature that has fascinated scientists for centuries. From ancient times to modern theories, the study of magnetism continues to reveal new insights into the fundamental forces of nature.