2500 Years of Magnetism

Here in the Superconductivity and Magnetism Group at Warwick we have been working towards understanding the properties of a range of different magnetic materials for over 20 years. The history of the study of magnetism, however, dates back over 2500 years to the earliest recorded times.

Magnetism - 600 BC to 1600 AD

In China and India, magnets were used from as early as the 4th century BC for navigationLink opens in a new window and medicinal purposes, while magnetic materials were discussed in ancient Greece by Thales around 600 BC.

Over the next two thousand years, magnets were used for compass navigationLink opens in a new window by both traders and explorers from Europe, North Africa, and Asia.

The lodestone spoon compassLink opens in a new window.

Age of Enlightenment

In 1600, the British physicist William Gilbert’s treatise on magnetism, De Magnete, Magneticisque Corporibus, et de Magno Magnete TellureLink opens in a new window, laid out the first scientific understanding of some aspects of magnetism.

William Gilbert, 1544 - 1603.

(Electro)magnetism in the 19th Century

Work by OerstedLink opens in a new window, AmpereLink opens in a new window, FaradayLink opens in a new window, GaussLink opens in a new window, BiotLink opens in a new window, SavartLink opens in a new window, and others began to develop our modern scientific understanding of magnetism, which culminated in 1861 with MaxwellLink opens in a new window’s equations.

Maxwell’s equations

$\nabla.E=\rho/\epsilon_0$ (Gauss's law),

$\nabla.B=0$ (Gauss's law for magnetism),

$\nabla\wedge\hspace{-0pt}E=-\frac{\partial\hspace{-1pt}B}{\partial\hspace{-1pt}t}$ (Faraday's law),

$\nabla\wedge\hspace{-0pt}B=\mu_0J+\mu_0\epsilon_0\frac{\partial\hspace{-1pt}J}{\partial\hspace{-1pt}t}$ (Ampere's circuital law with Maxwell's addition).

The giants of 19^th century (electro)magnetism.

Magnetism and Quantum Mechanics

A microscopic theory of magnetism required the development of quantum mechanics. This includes the PauliLink opens in a new window exclusion principle, and exchange theory of HeisenbergLink opens in a new window and DiracLink opens in a new window.

Pioneering work by LangevinLink opens in a new window, CurieLink opens in a new window, WeissLink opens in a new window, and KramerLink opens in a new window, and then later by NeelLink opens in a new window, van VleckLink opens in a new window, MottLink opens in a new window, and P. W. AndersonLink opens in a new window, among others, led to an understanding of behaviour of the magnetic materials in the disordered (paramagnetic) and ordered ferro-, ferri-, and antiferro-magnetic state.

20^th (and 21^st) century magneticians.

Magnetism and the Nobel Prize in Physics

1932 - HeisenbergLink opens in a new window,

1933 - Schrodinger and DiracLink opens in a new window,

1945 - PauliLink opens in a new window,

1977 - Anderson, van Vleck and MottLink opens in a new window,

2007 - Fert and GrunbergLink opens in a new window

Modern Applications of Magnetism

Modern developments in applied magnetism were driven, in part, by the need to store and read data.

This work included the discovery of giant magnetoresistance (GMR), the quantum and spin Hall effects and all their anomalous counterparts, and led to the development of hard discs with terabyte storage capacity and magnetic RAM.

Parallel research efforts led to the development of permanent magnetic materials used in motors, actuators, switches and generators, speakers and microphones, as well as many other niche applications.

Today, the market for soft, semi-hard, and hard magnetic materials is growing, with new applications such as cloud computing and electric cars. Companies including Hitachi, Molycorp, and TDK, share a market for magnetic materials that was estimated to be $100 bn per annum worldwide in 2020.