The ability of a permanent magnet to support an external magnetic field is due to crystal anisotropy within the magnetic material that "locks" small magnetic domains in place. Once the initial magnetization is established, these positions remain the same until a force exceeding the locked magnetic domain is applied, and the energy required to interfere with the magnetic field produced by the permanent magnet varies for each material. Permanent magnets can generate extremely high coercivity (Hcj), maintaining domain alignment in the presence of high external magnetic fields. Stability can be described as the repetitive magnetic properties of a material under specified conditions over the life of the magnet. Factors that affect magnet stability include time, temperature, changes in reluctance, adverse magnetic fields, radiation, shock, stress, and vibration.

Time has little effect on modern permanent magnets, which studies have shown change immediately after magnetization. These changes, known as "magnetic creep," occur when less stable magnetic domains are affected by thermal or magnetic energy fluctuations, even in thermally stable environments. This variation decreases as the number of unstable regions decreases. Rare earth magnets are unlikely to experience this effect because of their extremely high coercivity. A comparative study of longer time versus magnetic flux shows that newly magnetized permanent magnets lose a small amount of magnetic flux over time. For more than 100,000 hours, the loss of samarium cobalt material is basically zero, while the loss of low permeability Alnico material is less than 3%.