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Muon spin rotation experiments performed on superconducting La2-xSr x Cu04 samples clearly show that internal magnetic fields coexist at low temperatures (T < 2 K) with superconductivity for x<0.15. The magnetic fields in the superconducting state are an order of magnitude smaller than the corresponding fields in undoped La2CuC>4. The data are discussed in the context of a magnetic pairing mechanism in high-TV superconductors.

Structural Studies on Three Modifications of FeMo04 1093 NdTe218 may be described as a tricapped trigonal prism.The sulfur atoms in Gd2Ss are all coordinated by five gadolinium atoms. A trigonal-bipyramidal arrangement is found for S(l) with average S-Gd distances of 2.90 Á, and S(2) and S(3) are in square pyramids with average S-Gd distances of 2.85 and 2.83 Á, respectively. Figure 2 shows the coordination polyhedra associated with each atom. The S-S distances are all greater than 3.40 Á except for one of 3.04 Á between S(2) and S(3) centered around the point 0.37, 0.48, 3/4 in Figure 1. This short S(2)-S(3) distance represents a polyhedral edge shared between two Gd(l) polyhedra and one Gd(2) polyhedron and is the only edge shared by more than two of the gadolinium polyhedra. There are, however, no unusually short Gd-Gd distances in the (18) R. Wang, H. Steinfink, and W. F. Bradley, Inorg. Chem., 5, 142 (1966).structure, the shortest being one of 3.888 Á between Gd(l) and Gd(2). This is consistent with the magnetic data7 which indicate very weak interactions between gadolinium atoms. For Gd2Ss there are no magnetic transitions down to 4.2°K, the Curie-Weiss constant ( ) is -8°K, and the observed moment of 7.94 ± 0.01 BM is in excellent agreement with the calculated value19 of 7.94 BM. Recently, a structure for monoclinic Ho2S3 has been reported20 which contains half of the Ho in octahedral and half in sevenfold coordination. Thus the coordination of the rare earth is showing a general tendency to increase as the size of the rare earth increases, going from six in the corundum type, through mixed six and seven in the monoclinic type, to mixed seven and eight in the orthorhombic type.