| In this Dissertation, I combined neutron scattering with susceptibility, and transport measurements on two types of high-temperature superconductors La2-xBa xCuO4, and Fe1+yTe 1-xSex to study the interplay between magnetism and superconductivity. By studying La 2-xBaxCuO 4 with crystals grown by a floating-zone technique, it is found that static magnetic order competes with superconductivity, with the observation that both magnetic field and Zn impurity reduce the superconductivity and enhance the magnetic order. By studying the doping and magnetic-field dependence on Fe1+yTe1- xSex with crystals grown by a horizontal unidirectional solidification method, it is revealed that magnetic fluctuations are essential for superconductivity. The results are consistent with the idea that magnetic excitations act as the "glue" to pair the electrons, and render the superconductivity. |
