History of Magnetism

We all see magnetism all around us, right from the fridge magnets to a computer hard disk.
This article discusses how the word magnetism came into existence and how its
understanding has evolved among human beings.

Origin of the word Magnetism

The word magnetism comes from a Greek word “magnētis” which means “stone from
Magnesia”, a place in Thessaly, Greece. This place of Greece has the natural deposits
of the lodestone (scientific name magnetite or Fe\(_3\)O\(_4\) . From the Greek word, it
transformed and reached the Latin language as “magnes” and passed on as
“magnetism” in old French and finally became “magnetism” in English around the
16\(^{th}\) century.

First understanding and application of magnetic material

A small piece of lodestone was suspended or floated in water to align in the north-
south direction. With time, sailors learnt that if the iron needle is magnetized with a
lodestone, it can give the same results when suspended in water. This floating
magnetized needle in water is known as a compass. The first book on magnetism was
published in 1600 by William Gilbert, De Magnete, Magneticisque Corporibus, et de
Magno Magnete Tellure (On the Loadstone and Magnetic Bodies and on the Great
Magnet the Earth). In this book, this English physician of Elizabeth I laid the
foundations of the Earth being a giant magnet and studied loadstone and its relation
with electricity in its early stages. William Gilbert is also called the father of
magnetism, and while observing the lodestone, he observed that after removing the
lodestone from the external field, it rotated along the direction of the external field.
This phenomenon persists at the quantum level in the single-spin moment behaviour.

Ancient exploration of magnetic lodestone

Sailors used this magnetic loadstone to magnetize small iron needles to get the north
and south directions when the sun and stars are not visible. The earliest use of these
compass needles was in China from the 2\(^{nd}\) BCE to the 1\(^{st}\) Century CE. While trade
from China, India, and Islamic mariners likely introduced this directional equipment.
In Indian Sanskrit scripts, it was known as “matsya-yantra” as floating iron needles of
fish shape were used. From the Islamic world, it reached Europe. The first account of
the compass in European literature comes in the 12\(^{th}\) century in the book “De naturis
rerum”, by Alexander Neckam.

Magnetism as a perspective of living beings on Earth

Magnetism is also used by living beings for navigation, like the migration of birds,
crabs, and certain worms. Earth’s magnetic field has not been static but has evolved
with time, and even flipped its orientation, as geological rock specimens explain. This
Earth’s magnetic field is not only used in adaptation of the living beings, but also one
of the reasons of life on Earth, and a natural phenomenon, Aurora, which forms when
the magnetic field protects living creatures from the Sun’s life-threatening solar flares.

Contribution of various scientists in understanding magnetism

Various scientists contributed to understanding the fundamentals and applications of
magnetism to revolutionize the world at each stage. The discovery of the loadstone
laid the path of the field of magnetism in ancient times. In the 18 th Century, extensive
studies on this phenomenon by Ørsted, Ampère, Gauss, Faraday, and Henry were
performed that relate electricity and magnetism and explain the co-dependency. The
theoretical understanding of electromagnetism comes from Maxwell’s equations by
James Clerk Maxwell, a 19\(^{th}\) century Scottish scientist. These equation plays an
important role in electromagnetism as Newton’s laws in classical mechanics. The
experimental proof of Maxwell’s equations was done by Heinrich Hertz by the
generation and detection of radio waves (electromagnetic waves). How the magnetic
materials lose their magnetism after heating to a certain temperature, as understood
and stated by Pierre Curie, is known as the Curie temperature. The scientific
explanation of paramagnetism and diamagnetism was given using statistical
mechanics that were evolving in the 19\(^{th}\) century by Paul Langevin, a French
scientist. Although scientists were trying to understand magnetism, the ferromagnetic
materials were still not ready to be deciphered with classical physics theories, as the
magnetic properties have more duality than just induced from dynamic electric fields.
As quantum physics evolved, a better understanding of superposition, quantization of
the energy levels in atoms, and spin operators with a probabilistic approach,
symmetric and asymmetric wavefunctions in physics built the fundamentals to
decipher this Rosetta stone of the load stone. Modern physicists like Pierre Weiss,
Werner Heisenberg, Lev Landau, Louis Néel, and Bloch used quantum tools to
explain exchange interaction in the ferromagnets, phase transition from the magnetic
to non-magnetic states, canting of magnetic moments, and dynamic magnetic fields
with quanta magnons. End of the 20\(^{th}\) century and 21\(^{st}\) century scientists discovered
phenomena like Giant magnetoresistance (GMR), exchange bias, topological magnetic
texture, and a new subfield of magnetism, spintronics, with the power to make this
century much energy efficient in terms of computing and the storage which is needed
in this era of Artificial Intelligence.

References

1. Coey, John MD. Magnetism and magnetic materials. Cambridge university press, 2010.
2. Neckam, Alexander. De naturis rerum, libri duo: With the Poem of the Same Author, De laudibus divinae sapientiae. Cambridge University Press, 2012.
3. Chikazumi, Sōshin, and Chad D. Graham. Physics of ferromagnetism. No. 94. Oxford university press, 1997.