Magnetic vs Non-Magnetic Materials
Some materials like iron are strongly attracted to magnets while others like plastic are not affected at all. What causes this difference in magnetic behavior? Read on to find out what makes a material magnetic or non-magnetic.
Origin of Magnetism – Electron Spin
Magnetism arises from the spin and orbital motion of electrons. Electrons act like tiny spinning magnets producing their own magnetic field. In most materials, the electron spins are randomly oriented, so their tiny magnetic fields cancel out resulting in no net magnetism.
However, in some materials like iron, electron spins align parallel to each other within specific regions called domains. Their microscopic magnetic fields add up to produce a macroscopic field that exerts measurable magnetic force. Materials with electron spin alignment are magnetic.
Ferromagnetic Materials
Materials like iron, cobalt and nickel that exhibit strong magnetism even without an external field are called ferromagnetic. Their magnetic domains are easily aligned by an external magnetic field, producing a strong attraction. The domains remain aligned after the external field is removed, creating a permanent magnet.
Paramagnetic and Diamagnetic Materials
Materials like aluminum and platinum are weakly attracted to magnets. Their domains are randomly oriented but can align slightly with an external magnetic field – these are paramagnetic. Materials like copper and carbon are weakly repelled by magnets. Their domains align opposite to an external field – these are diamagnetic.
The domain alignment is temporary. When the external field is removed, thermal motion randomizes the domains again. So paramagnetic and diamagnetic materials are non-permanent magnets.
Atomic Structure Effects
The magnetic properties arise from a material’s electronic configuration – how the electrons are arranged within the atoms. Materials with partially filled electron shells like iron can have aligned spins and become ferromagnetic. Materials with full shells have randomized spins and are non-magnetic.
The orbitals also affect magnetism. Orbitals that are spherical or fully filled do not contribute to magnetism. Non-spherical partially filled orbitals allow spin alignment and produce magnetism.
The Magnetic-Nonmagnetic Distinction
In summary, inherent magnetism arises when the spins of unpaired electrons in a material align parallel within domains. This happens in materials like iron which have partially filled electron shells and orbitals. Other materials have randomized electron spins and exhibit weak to no magnetism. Understanding the source of magnetism in electron spin and structure is key to designing new magnetic materials.