Directional Vortex Pinning at Microwave Frequency in YBa2Cu3O7−x Thin Films with BaZrO3 Nanorods
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We investigate the effect of the anisotropy and of the directional pinning in YBa2Cu3O7−x films grown by pulsed laser ablation from targets containing BaZrO3 at 5 mol%. BaZrO3 inclusions self-assemble to give nanorods oriented along the c-axis, thus giving a preferential direction for vortex pinning. The directionality of vortex response is studied at high ac frequency with the complex microwave response at 48 GHz, as a function of the applied field and of the angle θ between the field and the c-axis. The complex microwave response does not exhibit any angular scaling, suggesting that the structural anisotropy of YBa2Cu3O7−x is supplemented by at least another preferred orientation. The pinning parameter r shows evidence of directional pinning, effective in a wide range of angles around the c-axis (thus ascribed to BZO nanocolumns).
KeywordsVortex pinning Anisotropy Nanorods BaZrO3
We thank S. Schweizer for the help in taking data. This work has been partially supported by the FIRB project “SURE:ARTYST” and by EURATOM. N.P. acknowledges support from Regione Lazio.