Iron-based superconductor

[2][3] In 2008, led by recently discovered iron pnictide compounds (originally known as oxypnictides), they were in the first stages of experimentation and implementation.

[4] (Previously most high-temperature superconductors were cuprates and being based on layers of copper and oxygen sandwiched between other substances (La, Ba, Hg)).

A subset of iron-based superconductors with properties similar to the oxypnictides, known as the 122 iron arsenides, attracted attention in 2008 due to their relative ease of synthesis.

The crystalline material, known chemically as LaOFeAs, stacks iron and arsenic layers, where the electrons flow, between planes of lanthanum and oxygen.

Replacing up to 11 percent of the oxygen with fluorine improved the compound – it became superconductive at 26 kelvin, the team reports in the March 19, 2008 Journal of the American Chemical Society.

Subsequent research from other groups suggests that replacing the lanthanum in LaOFeAs with other rare earth elements such as cerium, samarium, neodymium and praseodymium leads to superconductors that work at 52 kelvin.

[5]Iron pnictide superconductors crystallize into the [FeAs] layered structure alternating with spacer or charge reservoir block.

[12] The compounds can thus be classified into "1111" system RFeAsO (R: the rare earth element) including LaFeAsO,[3] SmFeAsO,[14] PrFeAsO,[22] etc.

[18] In 2009, it was shown that undoped iron pnictides had a magnetic quantum critical point deriving from competition between electronic localization and itinerancy.