Putting solid oxygen under pressure leads to a phase transition that squeezes out oxygen's magnetism. Solid oxygen is the only molecularly magnetic element. At atmospheric pressure it is an anti-ferromagnetic insulator but becomes a metallic superconductor at high pressure. Now, Igor Goncharenko of the Léon Brillouin Laboratory in Saclay, France, and colleagues have put solid oxygen under 80000 atmospheres and observed it reverting to a non-magnetic material. Their findings could provide astronomers with important clues about the interiors of the so-called "gas" giants, Jupiter and Saturn. These planets are thought to have solid cores composed of insulating solids of oxygen, nitrogen, and hydrogen.
Oxygen's magnetism under pressure