Pierre Curie was a French physicist best known for his work on radioactivity. In 1898, Pierre and his wife Marie Curie presented evidence for the discovery of an additional very active substance that behaved chemically almost like pure barium. They suggested the name of radium for the new element, and henceforth were identified with the discovery of radiation. For this the Curies were awarded the Nobel Prize in physics (1903), which they shared with Henri Becquerel, who was awarded half the price. Pierre also discovered the effect of temperature on paramagnetism, which is now known as Curie's law. Moreover, he proved that ferromagnetic substances exhibited a critical temperature transition, above which the substances lost their ferromagnetic behavior; this is now known as the Curie point. With his brother Jacques, he discovered the piezoelectric effect, namely, crystals that acquire a charge when compressed, twisted or distorted. The curie is a unit of radioactivity (3.7 x 10¹⁰ decays per second or 37 gigabecquerels) originally named in honor of Pierre Curie by the Radiology Congress in 1910.