We describe an effective method for discovery of new superconductors, which combines phase‐spread alloy thin film preparation with a magnetic field modulated (MFM) microwave absorption technique. The MFM technique can detect superconductivity in YBa2Cu3O7−&dgr;volumes as small as 5×10−11cm3. As an illustration, PrxGd1−xBa2Cu3O7−&dgr;thin films with varyingxwere simultaneously grown on the same substrate using a phase‐spread alloy technique. The onset temperature determined from the microwave absorption agrees with resistivity, Auger spectroscopy, and energy‐dispersive x‐ray microanalysis data. When phase‐spread Lax(NiB)1−xNyfilms (0<x<1) were grown at several different N partial pressures and temperatures, no superconductivity was detected except that of pure La. In contrast, superconductivity was detected in Yx(NiB)1−xCyfilms grown on MgO. ©1995 American Institute of Physics.