Microwave properties of YBa${}_2$Cu${}_3$O${}_{7-\delta }$ films with BaZrO${}_3$ nanoinclusions

We present measurements of the microwave complex surface impedance at 47.7 GHz in YBa${}_2$Cu${}_3$O${}_{7-\delta }$ (YBCO) films deposited by pulsed laser deposition with the explicit goal to introduce BaZrO${}_3$ (BZO) nanoinclusions. Composite targets obtained by addition of BZO powder in molar percents ranging from 2.5 to 7 mol.% have been prepared and characterized. Measurements of the microwave surface impedance indicate a broadened transition in zero field, however compensated by a very large pinning frequency, indicating that while intergrain properties are still to be optimized the effect of nanometric inclusions substantially enhances the intragrain vortex pinning.