By Claire Gillespie | May 6, 2023 2:21 am EST
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Magnets bond with metals that possess strong magnetic traits—chiefly iron, nickel, and cobalt. Metals like aluminum, brass, copper, and lead are weakly magnetic or non‑magnetic, so magnets do not stick to them.
A magnet is a piece of material that can attract or repel other magnetic objects. The Earth itself behaves as a gigantic magnet, with a north‑seeking and a south‑seeking pole surrounded by a magnetic field. On the atomic level, electrons spin around the nucleus, creating tiny magnetic moments. In most materials these moments cancel out, but in certain metals they align, producing a net magnetic effect.
Diamagnetic substances have no permanent magnetic moment; they produce a weak repulsive effect when exposed to a magnetic field. Examples include copper, water, and bismuth.
Paramagnetic materials have unpaired electrons that align with an external field, producing a weak attraction. Common paramagnets are aluminum, magnesium, and titanium.
Ferromagnetic metals contain large numbers of aligned magnetic moments, making them strongly attracted to magnets. Key examples are iron, nickel, cobalt, and most steel alloys. Some ferromagnets are “magnetically soft” (easily magnetized and demagnetized) while others are “magnetically hard” and retain permanent magnetism.
These are the classic ferromagnetic metals: iron, cobalt, nickel, steel (mostly iron), manganese, gadolinium, and natural lodestone. Alloys such as AlNiCo (aluminum, nickel, cobalt) and rare‑earth steels (samarium‑neodymium) are engineered to be permanent magnets. Their crystal structure locks magnetic domains in place, though heat or corrosion can disrupt this alignment.
Aluminum, brass, copper, gold, lead, and silver are naturally non‑magnetic or only weakly magnetic. Even a small iron addition can magnetize a normally non‑magnetic metal. Stainless steel is a special case: austenitic stainless (high nickel) is non‑magnetic, while ferritic stainless (high chromium) retains magnetism.
When a strong magnetic field is required, electromagnets are used. Coiling electric current through a conductor creates a magnetic dipole that can be tuned by adjusting the current. This method is independent of the metal’s intrinsic magnetic properties and allows the creation of extremely powerful fields.
