A new Ba 2 CuO 4-y superconductor with critical temperature (T c) exceeding 70 K was discovered. The X-ray absorption measurement gives evidence that this cuprate resembles La 2 CuO 4 but is doped with a fairly large amount of holes, while in contrast to the so far known hole-doped high-T c cuprates, the new cuprate possesses a much shorter local apical oxygen distance as well as much expanded in-plane Cu-O bond, leading to unprecedented compressed local octahedron. In compressed local octahedron, the Cu3d3z 2-r 2 orbital level will be lifted above the Cu3dx 2-y 2 orbital level with more three-dimensional features, implying that pairing symmetry may carry admixtures from more than one gap, suggesting that Ba 2 CuO 4-y composed of alkaline earth copper oxides that are the essential elements to form cuprate superconductors may belong to a new branch of cuprate superconductors.
We report a new diluted ferromagnetic semiconductor Li
1+y
(Cd,Mn)P, wherein carrier is doped via excess Li while spin is doped by isovalence substitution of Mn
2+
into Cd
2+
. The extended Cd 4
d
-orbitals lead to more itinerant characters of Li
1+y
(Cd,Mn)P than that of analogous Li
1+y
(Zn,Mn)P. A higher Curie temperature of 45 K than that for Li
1+y
(Zn,Mn)P is obtained in Li
1+y
(Cd,Mn)P polycrystalline samples by Arrott plot technique. The p-type carriers are determined by Hall effect measurements. The first principle calculations and X-ray diffraction measurements indicate that occupation of excess Li is at Cd sites rather than the interstitial site. Consequently holes are doped by excess Li substitution. More interestingly Li
1+y
(Cd,Mn)P shows a very low coercive field (<100 Oe) and giant negative magnetoresistance (~80%) in ferromagnetic state that will benefit potential spintronics applications.
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