Abstract
In this work, we reported that the resistances of the single-phase Sr2YRu1-xCuxO6 (x= 0.05, 0.10, 0.15) samples are measured under magnetic field. The zero-resistance temperature shifted toward lower temperature with increasing field but saturated in the high field regime. So the field effect on Tc at high field is less effective for the zero resistance compared with the onset temperature. This is very different than all other known superconducting systems.Magnetic measurements show that the possible coexistence of superconductivity and magnetic order in this 2116 system and also show it by using the low field microwave absorption and ESR probe measurement. On the other hand, we do not observe clearly the feature that related to the electron spin resonance signal of high spin-ion Ru, but only observe a broad signal that may originate from free electron. It has been shown to be measurable from the ESR broadening of ESR probes adsorbed on the surface of the superconductive sample. The microwave absorption is reflection of the distribution of Josephson junctions with varying dimensions. We demonstrate the low field microwave absorption technique is also a sensitive method to determine the existence of magnetic order.The results present in this thesis clearly show the coexistence of superconductivity and magnetism in the 2116 double perovskites. The superconducting transition temperature is of the same order as that of the magnetic order and the superconductivity is likely to be with p-wave symmetry. This is consistent with the presence of a canting magnetic order, which originates from the coexistence of an antiferromagnetic order and ferromagnetic order. The spin fluctuation of the former may provide the necessary attraction and the spin polarization of the band from the latter makes equal spin pairing likely.