Only ferromagnetic metals-primarily iron, nickel, and cobalt-are strongly attracted to magnets. These materials retain their magnetic alignment after exposure to a magnetic field, enabling permanent magnets and magnetic storage.
Ferromagnetism arises from unpaired electrons in atomic orbitals. When exposed to a magnetic field, electron spins align in the same direction, creating a net magnetic moment. This alignment persists in some materials after the external field is removed, resulting in permanent magnetization.
Iron, nickel, and cobalt are the only elemental metals that exhibit ferromagnetism at room temperature. Other metals like gadolinium show it only below 20°C, making them impractical for everyday applications. Materials such as steel-a mixture of iron and carbon-retain magnetic properties due to iron's dominance.
Magnets generate a magnetic field that exerts force on moving electric charges. In ferromagnetic materials, this field causes electron spins in atoms to align. The aligned spins produce microscopic magnetic domains that grow larger under an external field, increasing attraction.
When a magnet approaches iron, the domains within the iron realign to match the field direction. This creates an induced magnetic pole opposite the approaching magnet pole, causing attraction. Once the external field is removed, most ferromagnetic materials lose their alignment unless they are hardened into permanent magnets.
Non-magnetic metals such as aluminum, copper, gold, and silver do not form aligned domains. They may weakly repel or attract magnets due to eddy currents or paramagnetism, but these forces are negligible compared to ferromagnetic attraction.
The following table outlines common magnetic materials and their composition:
| Metal/Alloy | Composition | Magnetic Response | Common Uses |
|---|---|---|---|
| Iron | Pure Fe | Strongly ferromagnetic | Electric motors, transformers, magnetic cores |
| Nickel | Pure Ni | Ferromagnetic below 358°C | Coins, plating, alloy steel |
| Cobalt | Pure Co | Ferromagnetic below 1121°C | High-strength alloys, MRI components |
| Steel (carbon steel) | Fe + 0.2-2.1% C | Ferromagnetic | Construction, tools, vehicle parts |
| Alnico | Al + Ni + Co + Fe | Permanent magnet | Speakers, sensors, vintage motors |
Some alloys, like alnico (aluminum-nickel-cobalt), maintain strong magnetism even without an external field. These are used in permanent magnets for speakers and electric meters. Stainless steel varies: austenitic grades (e.g., 304) are non-magnetic due to high nickel content, while martensitic grades (e.g., 430) remain magnetic.
A key distinction often missed: not all iron-containing materials are magnetic. For example, rust (iron oxide) is not attracted to magnets because its crystal structure disrupts domain alignment. Similarly, powdered iron can be non-magnetic if particles are too small to sustain coherent domains.
Many assume all metals are magnetic. Aluminum, despite being conductive, shows no attraction to standard magnets. A 10-gram neodymium magnet will not move an aluminum can, though it may induce weak eddy currents that slow motion during fall.
Another error: believing that magnetism requires electricity. Permanent magnets work without power. Electromagnets require current, but the magnetic field still stems from aligned electron spins in the core material-usually iron or iron-based alloys.
One non-obvious fact: temperature affects magnetic behavior. Iron loses ferromagnetism above 770°C (its Curie point), becoming paramagnetic. Below this threshold, domains form and sustain alignment. This property enables industrial heat treatment processes that alter magnetic strength in steel components.
In recycling facilities, conveyor belts pass shredded waste through a rotating drum magnet. Ferromagnetic metals like iron and steel are pulled from the stream and collected separately. Non-magnetic materials-copper, aluminum, plastics-continue down the line.
A typical system uses a 1.5 Tesla rare-earth magnet. With a 100 kg/min feed rate, recovery efficiency exceeds 95% for ferrous metals. Non-ferrous metals like brass or lead remain unaffected. This process reduces landfill volume and increases material value.
I've observed this setup in a scrap yard in Toledo, Ohio. During a visit, we tested a piece of car body with a handheld magnet-it stuck firmly. A similar piece made of aluminum did not. The difference was clear: only ferromagnetic metals responded.
Understanding what metal is attracted to magnets hinges on identifying ferromagnetic elements. Iron, nickel, and cobalt are the only pure metals with strong attraction at room temperature. Alloys based on these elements extend utility in motors, sensors, and industrial sorting systems. Always test with a known magnet-some stainless steels behave unpredictably.