Suchergebnisse

We have studied the interaction between magnetism and superconductivity in a pseudo-spin-valve structure consisting of a Co/Cu/Py/Nb-layer sequence. We are able to control the magnetization reversal process and monitor it by means of the giant magnetoresistance effect during transport measurements. By placing the superconducting Nb-film on the top of the permalloy (Py) electrode instead of putting it in between the two ferromagnets, we minimize the influence of spin scattering or spin accumulation onto the transport properties of Nb. Magnetotransport data reveal clear evidence that the stray fields of domain walls (DWs) in the pseudo-spin valve influence the emerging superconductivity close to the transition temperature by the occurrence of peaklike features in the magneto-resistance characteristic. Direct comparison with magnetometry data shows that the resistance peaks occur exactly at the magnetization reversal fields of the Co and Py layers where DWs are generated. For temperatures near the superconducting transition the amplitude of the DW-induced magnetoresistance increases with decreasing temperature, reaching values far beyond the size of the giant magnetoresistive response of our structure in the normal state. 2012 American Physical Society. ; We acknowledge the Diputación Foral de Giupuzkoa Ref. 99/11, program Red Guipuzkoana de Ciencia Tecnologia e Innovacion, funding from the Basque Government under Program No. PI2009-17 and UPV/EHU Project IT-366-07, and the Spanish Ministry of Science and Innovation under Projects No. MAT2009-07980 and FIS2011-28851-C02-02. ; Peer Reviewed

We report unexpected enhancements of the magneto-optical effect in ferromagnetic Permalloy disks of diameter D < 400 nm. The effect becomes increasingly pronounced for smaller D, reaching more than a 100% enhancement for D ¼ 100 nm samples. By means of experiments and simulations, the origin of this effect is identified as a nanoscale ring-shaped region at the disk edges, in which the magneto-optically induced electric polarization is enhanced. This leads to a modification of the electromagnetic near fields and causes the enhanced magneto-optical excitation, independent from any optical resonance. ; We acknowledge funding from the Basque Government (Program No. PI2012-47) and the Spanish Government (Project No.MAT2012-36844).Work at the Universidad de Cantabria has been supported by MICINN under Project No. FIS2013-45854-P.