The strongest magnets available for purchase are permanent magnets, which maintain a magnetic field without an external power source. These are not the massive, superconducting electromagnets found in particle accelerators or MRI machines, which are specialized, non-commercial devices. For consumers and industrial users seeking maximum magnetic force, understanding this category of commercially sold permanent magnets is essential.
Neodymium The Strongest Commercially Available Magnet
The strongest permanent magnets on the market today are constructed from an alloy known as Neodymium Iron Boron (NdFeB). This rare-earth material has a specific tetragonal crystalline structure that allows it to store immense magnetic energy. The power of these magnets stems from their high maximum energy product (\(\text{BH}_{\text{max}}\)), which represents the maximum energy density the material can supply to an external magnetic circuit.
These magnets are classified into grades, typically beginning with the letter ‘N’, such as N35, N42, or N52. The number following the ‘N’ directly correlates with the \(\text{BH}_{\text{max}}\) value in Mega Gauss Oersteds (MGOe). For example, an N52 magnet is significantly stronger than an N35 of the same size. While Neodymium magnets offer unparalleled strength, standard grades can begin to lose strength above approximately 80°C (175°F).
Understanding Magnet Strength Metrics
Magnet strength is quantified using several technical measurements. One fundamental metric is Residual Induction (Br), measured in Gauss or Tesla, which represents the magnetic flux density remaining in the magnet after the magnetizing force has been removed. This value indicates the inherent magnetic field density of the material.
Another important property is Coercivity (Hci), measured in Oersteds, which describes the magnet’s resistance to demagnetization by an external magnetic field or heat. The overall performance indicator, \(\text{BH}_{\text{max}}\), is derived from a combination of the Br and Hci values, providing a single number to compare the magnetic power of different materials.
For the average consumer, the most practical measurement is Pull Force. Pull Force is the physical force, measured in pounds or Newtons, required to detach the magnet from a flat, thick steel plate with direct surface-to-surface contact. This metric provides a real-world indicator of how much weight a magnet can hold, making it the most relevant specification for purchasing decisions.
Practical Safety and Handling Guidelines
The extreme power of Neodymium magnets necessitates strict adherence to safety protocols to prevent serious injury and property damage. The most immediate physical hazard involves the risk of severe pinching or crushing injuries. Larger magnets can snap together from a distance with enough force to break bones or severely pinch flesh. The material is also brittle and can shatter upon impact, sending sharp fragments into the air.
The powerful magnetic fields can also interfere with and permanently damage sensitive electronic devices and magnetic media. Keep these magnets away from computers, hard drives, credit cards, mobile phones, and especially medical implants such as pacemakers. For proper storage, magnets should be kept separated by non-magnetic spacers or stored with soft iron “keepers” to contain the magnetic field.
A particularly dangerous risk involves the ingestion of multiple small magnets, especially by children. If two or more magnets are swallowed, they can attract one another across intestinal walls, creating a tight pinch that leads to tissue death, perforation, and life-threatening complications.
To maintain their longevity, Neodymium magnets should be stored in a cool, dry environment. They are susceptible to corrosion and can lose their magnetic properties irreversibly if exposed to temperatures exceeding their maximum operating limit.