What Makes A Magnet Work?... What Is Magnetism?

Back in the sixth century B.C. the Greek philosopher, Thales, concluded that to act in the "willful way it did, a magnet had to have a soul." He was right about enough things to earn the name "The Father of Philosophy," but he wasn't right about that one. Many other theories were expounded over the years, but the puzzle of magnetism didn't really start to come together until William Gilbert's monumental treatise on magnetism was published in 1600. Though this seminal work has been called an "epoch-making contribution to human advancement" (it earned him the name, "The Father of Magnetism"), some things hadn't changed in 2400 years. The magnet, he said, "hath a soul."

By the nineteenth century, a number of great scientists were putting the experimental method to work on magnetism, with results that have echoed down to the present day. First Hans Christian Oersted discovered the relationship between electricity and magnetism. Then, Michael Faraday determined that though magnets seem to act directly on one another, they actually act by means of intermediary fields. The electromagnetism discovered by Oersted is widely used in all industrial settings today, and both permanent magnets and electromagnets are now designed to produce the magnetic fields Faraday first described in specific shapes, depths and strengths, depending on the magnet's purpose.

The discovery of the electron later in the century added a large piece to the puzzle, for it is the arrangement of electrons in the atom that determines whether substances are magnetic or not. Iron, cobalt, nickel and some rare-earth groups are highly magnetic, or "ferromagnetic," because they have uncompensated electron spins and certain dimensional characteristics which create a magnetic "moment," or force. The magnetic moments in neighboring atoms join together to create magnetic regions called "domains." Since all these atoms have their magnetic moments aligned, these domains themselves become magnets. These smallest known permanent magnets (6000 would fit on the head of a pin) are randomly oriented in unmagnetized ferromagnetic material, but in a magnet the domains are aligned, created the external force we know as magnetism.

Applying an external magnetic field to a ferromagnetic material can cause the random domains to become aligned, magnetizing the material. This is what happens when you put a paper clip near a magnet the paper clip becomes a magnet itself. With soft magnetic materials such as iron, small external fields will cause great alignment, but because of the small restraining force only a little of the magnetism will be retained when the external field is removed. With hard (permanent) magnetic materials such as Alnico (an alloy consisting of various amounts of iron, nickel, aluminum, cobalt, copper and titanium) a greater external field must be applied to cause orientation of the domains, but most of the orientation will be retained when the field is removed, thus creating a strong permanent magnet. Permanent magnets for industrial use are made of hard magnetic materials like Alnico or of Strontium or Bariudar Ferrite in ceramic pressings.