Magnetism Home

All materials have some magnetic properties. The magnetic properties of matter largely depend upon how the electrons orbiting the nuclei of atoms behave. Diamagnetism is a  weak effect common to all substances and results from the orbital motion of electrons. In certain substances this is marked by a stronger effect, paramagnetism, due to electron spin. Some materials such as iron also display ferromagnetism.

MAGNETISM: A historical survey

The magnetic phenomenon has been known since antiquity. The ancient Greek knew about the magnetic force of both magnetite and rubbed amber. Magnetite, a magnetic oxide of iron mentioned in Greek texts as early as 800 BC, was mined in the province of Magnesia in Thessaly. Thales of Miletus is considered to have been the first man to study magnetic forces. According to Lucretius, a Roman philosopher in the first century BC, the term magnet was derived from the province of Magnesia. Pliny the Elder, however attributes it to the supposed discoverer of the material, the shepherd Magnes whose shoes and the tip of whose staff stuck fast in a magnetic field while he pastured his "the nails of flocks."

The oldest practical application of magnetism was the magnetic compass. Sometime in the 12th century, mariners in China and Europe made the discovery, apparently independently that a piece of lodestone, a naturally occurring magnetite ore, when floated on a stick in water, tends to align itself so as to point in the direction of the polestar. That was due to the fact that earth itself acts as an enormous bar magnet that forces freely moving magnets to take on the same orientation. The first experiments in magnetism are attributed to Petrus Peregrinus de Maricourt, a French engineer, who observed some of the fundamental properties of magnets. His famous letter on the magnet, 'Epistola Petri Peregrini di Maricourt ad Sygerum de Foucaucourt, militem, de magnete' (Letter on the magnet of Peter Peregrinus of Maricourt to Sygerus of Faucaucourt, Soldier), which he reportedly wrote to some friend while serving as an engineer in the army of Charles I of Anjou during a crusade in 1269, provides the first extant account of the polarity of magnets and the method for determining the north and the south pole of a magnet. His work is regarded as one of the great works of medieval experimental research and a precursor of modern scientific methodology.

The Renaissance brought with it a new found vigour for exploring and explaining phenomenon, that were previously known but never were fortunate enough to find someone’s discerning and observant eye. William Gilbert(1544 - 1603), a British physician, spent 17 years experimenting with electricity and magnetism and is rightfully acknowledged as the founder of the modern sciences of electricity and magnetism. He assembled the results of his experiments in the treatise "De Magnete, Magneticisque Corporibus, et de Magno Magnete Tellure".

Until the end of the 18th century, investigations in electricity and magnetism were mostly hypothetical in nature. The discovery of galvanic electricity and the development of voltaic electricity opened whole new areas for the 19th century by providing convenient sources of sustained electrical current. William Sturgeon, an English engineer devised the first electromagnet capable of supporting more than its own weight. This device led to the invention of the telegraph, the electric motor and numerous other devices basic to modern technology. George Green (1793 - 1841), an English mathematician, was first to attempt to formulate a mathematical theory of electricity and magnetism. The interesting fact of his life is that he was a baker before he became a mathematician, and that too through his own studies. His story truly reflects the scientific spirit of that age. The Danish physicist Hans Christian Orsted’s discoveries, in 1820, and those of André Marie Ampere, that led to the missing link between electricity and magnetism, greatly revolutionised the way how we view and understand the forces of nature. The merger was not only exciting itself but also fuelled efforts to unify the forces of nature and to interpret them as a single distinct force. Three closely related events led to this merger. First was Hans Christian Orsted’s accidental discovery of the influence of an electric current on a magnetic needle. The second event was Michael Faraday’s experimental proof that a changing magnetic field can induce a current in a circuit. The third was James Clerk
Maxwell’s prediction that a changing magnetic field has an associated electric field.

Maxwell’s theory received direct verification in 1886, when Heinrich Hertz of Germany detected the predicted electromagnetic waves, travelling at the speed of light, the waves he discovered are now known as the radio waves. Soon scientists became acquainted with a whole spectrum of electromagnetic waves. Following the discovery of electron, in 1898, electromagnetic theory became an integral part of the theories of atomic, subatomic and subnuclear structure of matters. In 1905 Albert Einstein’s special theory of relativity established beyond a doubt the both are aspects of one common phenomenon. These landmarks spurred a technological revolution in the development of electric power and radio communication.

RECENT DEVELOPMENTS:
After fully grasping the phenomenon of magnetism scientists set themselves to work on the magnetic properties of materials. Studies into magnetic properties of materials, especially of solid state crystalline materials resulted in a phenomenal rise in new technologies like the computer memory units. An important contribution to this field was by a French physicist Louis Eugene Felix Neel (1904 - ) who with the Swedish astrophysicist, Hannes Alfven, received the Nobel Prize for physics in 1970 for his pioneering studies of the magnetic properties of solids. His contributions to solid state physics have found numerous useful applications, particularly in the development of improved computer memory units. During the early 1930s he studied, on the molecular level, forms of magnetism that differ from ferromagnetism (a variety of magnetism in which the electrons spin in the same direction at low temperatures). Neel discovered that
in some substances alternating groups of atoms align their electrons in opposite directions, thus neutralising the net magnetic effect. This property is called antiferromagnetism. Neel’s studies of fine grain ferromagnets provided an explanation for the unusual magnetic memory of certain mineral deposits that in turn provided information on changes in the direction and the strenght of the earth’s magnetic field. Mainly because of his contributions, ferromagnetic materials can be manufactured to almost ant specifications for technical applications, and a flood of new synthetic ferrite materials has revolutionised microwave electronics.