Even Lanthanum Copper Oxide is Superconducting

The current excitement in superconductivity started with the discovery last year that lanthanum copper oxide when suitably doped with barium or strontium is a superconductor at temperatures up to 40 K. Now, researchers from France, IBM San Jose and Yorktown Heights and Bell Communications Research report that even the undoped lanthanum copper oxide is a superconductor with critical temperature up to 40 K. On the other hand, researchers at Exxon Research and Engineering Company have obtained definitive evidence for a transition to an antiferromagnetic phase in this compound (see figure, this page). Whether the low‐temperature phase of lanthanum copper oxide is antiferromagnetic or superconducting, researchers believe, depends very sensitively on lanthanum and oxygen concentrations.