Why Are Neodymium Magnets the Strongest Magnets on Earth?
Neodymium magnets have the highest maximum energy product of any permanent magnet material: up to about 52 MGOe for an N52 grade, compared with about 4 MGOe for ferrite (ceramic) magnets and 5 to 10 MGOe for alnico. In plain terms, a neodymium magnet packs the most magnetic force into the smallest size, and it resists being demagnetized.
The Two Numbers That Matter
High Remanence
After magnetizing, an N52 magnet keeps a flux density of about 1.4 to 1.5 tesla (14,300 to 14,800 gauss) inside the material.
High Coercivity
The Nd₂Fe₁₄B crystal resists being demagnetized, so the magnet can be made short and flat without losing its strength.
A Short History
Samarium cobalt magnets arrived in the late 1960s and 1970s. Neodymium magnets were developed independently by General Motors and Sumitomo Special Metals and announced in 1984. They were stronger and used cheaper, more plentiful materials, and they quickly spread into motors, speakers, hard drives and phones.
"Strongest" Means Strongest Permanent Magnet
Electromagnets and superconducting magnets, like those in MRI scanners, can produce stronger fields, but only while powered. Among magnets that need no power, neodymium is the strongest.