A magnet generates its own magnetic field, an invisible area of force that pulls on certain materials. This article explores which materials magnets interact with and the scientific principles behind these interactions.
Understanding Magnetic Attraction
The strong attraction of some materials to magnets lies in ferromagnetism, a property stemming from their atomic structure and electron behavior. Electrons possess “spin,” creating tiny magnetic moments within each atom. In ferromagnetic materials, these moments spontaneously align into magnetic domains. When an external magnetic field is applied, these domains align with the field, causing the material to become magnetized and attracted to the magnet.
Materials Magnets Attract
Magnets strongly attract ferromagnetic substances. The most common examples are iron, nickel, and cobalt. These elements, along with their alloys, form the basis for most magnetic applications. Steel, which is primarily an alloy of iron, also exhibits strong magnetic properties. Many everyday items are made from these ferromagnetic materials, such as refrigerator doors, various tools, and certain types of stainless steel.
Not all stainless steels are magnetic; austenitic stainless steels, for instance, are generally not magnetic, while ferritic and martensitic types are.
Materials Magnets Do Not Attract
The majority of materials are not strongly attracted to magnets and are classified as non-magnetic materials. Common examples include aluminum, copper, brass, gold, and silver. Other non-metallic substances like wood, plastic, and glass also fall into this category.
While these materials do not exhibit a noticeable attraction to magnets, all matter does respond to magnetic fields, albeit very weakly. Some materials are paramagnetic, meaning they are very weakly attracted to a magnet, such as aluminum. Others are diamagnetic, which means they are weakly repelled by a magnetic field, including water and copper. These weak magnetic properties are imperceptible in daily interactions.
Factors Affecting Magnetic Interaction
Several factors can influence the strength of a magnetic interaction with a ferromagnetic material. The distance between the magnet and the material is a significant factor. Magnetic force weakens rapidly as the distance increases. This decrease in force generally follows an inverse square or inverse cube law, meaning the force diminishes considerably over even short distances.
Temperature also plays a role in a material’s magnetic properties. As temperature increases, the magnetic strength of a magnet generally weakens. There is a specific temperature for each ferromagnetic material called the Curie temperature. Above this temperature, a ferromagnetic material loses its permanent magnetic properties and becomes paramagnetic, meaning it is no longer strongly attracted to a magnet.
The composition and purity of a material can also affect its magnetic response, as even small changes in alloying elements can alter its magnetic behavior.