Magnetism, a force influencing everything from compasses to advanced technology, prompts questions about the “most powerful magnet.” The answer isn’t singular; “powerful” depends on the magnet’s type, operation duration, and purpose. Different magnet categories hold various strength records.
How Magnet Strength is Measured
Magnetic field strength is quantified in units. The standard unit in the International System of Units (SI) is the Tesla (T), named after Nikola Tesla. Another common unit is the Gauss (G), with one Tesla equating to 10,000 Gauss. These units represent magnetic flux density, or the concentration of magnetic field lines.
Earth’s magnetic field is around 0.5 Gauss (30 to 65 microtesla). A common refrigerator magnet might register about 100 Gauss (0.01 Tesla). A junkyard magnet capable of lifting a car can reach 1 Tesla.
Permanent Magnets The Everyday Powerhouses
Permanent magnets maintain their magnetic field without an external power source. Neodymium magnets (NdFeB) are the strongest commercial magnets. These magnets are composed of neodymium, iron, and boron, forming an intermetallic compound with the chemical formula Nd2Fe14B. Their crystalline structure gives them high magnetic energy and demagnetization resistance.
Neodymium magnets come in grades, with N52 representing the strongest commercial grade. These magnets are used in everyday devices due to their strength and compact size. Common applications include headphones, motors, hard drives, and electronic devices. Some “open” MRI machines also incorporate large neodymium magnets.
Electromagnets Unlocking Extreme Fields
Electromagnets generate magnetic fields only when electric current flows. Superconducting magnets are the strongest continuous-field electromagnets, producing fields stronger than permanent magnets. They achieve this by using superconducting wires, which have zero electrical resistance when cooled to extremely low temperatures. This allows large currents to flow, creating powerful fields.
These high-field electromagnets are used in scientific and medical applications. Magnetic Resonance Imaging (MRI) machines operate with fields from 1.5 to 3 Tesla; research systems can reach 17 Tesla.
Particle accelerators like the Large Hadron Collider (LHC) use superconducting magnets for 8.3 Tesla fields, guiding high-energy particle beams. Fusion research facilities like the International Thermonuclear Experimental Reactor (ITER) use large superconducting magnets, such as its Central Solenoid, producing a 13 Tesla field. The National High Magnetic Field Laboratory in the United States operates a hybrid magnet that generates a continuous field of 45 Tesla, representing the world’s strongest continuous-field magnet.
Pulsed Magnets The Transient Record-Breakers
Pulsed magnets generate magnetic fields exceeding continuous-field magnets for brief durations. They rapidly discharge stored energy to create an intense pulse (microseconds to milliseconds). Such extreme fields often subject the magnet to strong forces, sometimes destroying it.
The highest non-destructive pulsed magnetic field reached 100 Tesla at the National High Magnetic Field Laboratory’s Pulsed Field Facility. This record-breaking magnet sustains its field for 15 milliseconds, allowing precise scientific measurements. Stronger fields are achieved in “destructive” experiments, where the magnet is sacrificed. One experiment generated a 1200 Tesla field, destroying the experimental chamber. These strong, transient fields are tools for research in material science and quantum physics, enabling study of material behavior under conditions not replicated by continuous fields.