superconductors (Type I)

Dutch physicist Heilke Kamerlingh Onnesdemonstrated that the resistance of some electrical conductors disappears suddenly at a temperature near absolute zero (-273° C), and he termed this phenomenon “superconductivity.” Superconductivity was first discovered in mercury in 1911; similar behavior has been found in approximately 25 other chemical elements, including lead and tin, and in thousands of alloys and chemical compounds. These 26 elements or Type 1 superconductors—characterized as the "soft" superconductors—were discovered first and require the coldest temperatures to become superconductive. They exhibit a very sharp transition to a superconducting state and "perfect" diamagnetism: the ability to repel a magnetic field completely.