Magnets are known for their ability to attract certain materials. This property is not universal, as magnets interact differently with various substances. Understanding what magnets stick to, and why, reveals insights into the atomic structure of materials and the scientific principles governing these interactions.
Materials Magnets Attract
Magnets primarily attract a specific group of materials known as ferromagnetic substances. The most common elements exhibiting strong magnetic attraction are iron, nickel, and cobalt. These three metals are naturally ferromagnetic at room temperature. Steel, an alloy predominantly made of iron, is a widely encountered example, such as in refrigerator doors and many tools.
Beyond these elemental metals, various alloys and compounds also display strong magnetic properties if they contain iron, nickel, or cobalt. For instance, certain types of stainless steel, which contain iron, can be magnetic depending on their specific composition and crystalline structure. Rare-earth elements like gadolinium and dysprosium are also ferromagnetic, particularly at lower temperatures, and are used in powerful modern magnets.
Materials Magnets Don’t Attract
Many common materials do not exhibit a noticeable attraction to magnets. This group includes a wide array of metals and non-metals. Examples of metals that magnets do not stick to include aluminum, copper, brass, gold, silver, and lead. These materials are often used in situations where magnetic interference needs to be avoided, such as in certain electronics or jewelry.
Beyond metals, everyday substances like wood, plastic, glass, paper, and rubber are also non-magnetic. Water does not visibly react to a magnet.
The Science Behind Magnetic Attraction
The ability of a material to stick to a magnet stems from a property called ferromagnetism. In ferromagnetic materials, atoms have tiny magnetic regions called domains. Within each domain, the magnetic moments of individual atoms are aligned in the same direction, acting like miniature magnets. In an unmagnetized ferromagnetic material, these domains are randomly oriented, causing their magnetic effects to cancel each other out.
When a magnet is brought near, its magnetic field causes these domains to rotate and align with the external field. This alignment creates a net magnetic force that attracts the material to the magnet. The strength of this attraction depends on how readily the domains can align and remain aligned. Materials that are not strongly attracted to magnets either lack these organized domains or their atomic magnetic moments are arranged in ways that cancel each other out, even in the presence of an external field.