Influencia del grado de deformación en frío en el tamaño de grano y en la resistencia a la corrosión del acero F-1110

En este trabajo se ha estudiado la evolución que sufre el tamaño de grano del acero al carbono F-1110 para distintos grados de deformación en frío, a partir de su estado de recocido, libre de tensiones y de cualquier acritud. La deformación en frío se ha conseguido utilizando una máquina universal de ensayos y los distintos grados de deformación se han ajustado al intervalo comprendido entre la estricción y la rotura. La posterior observación al microscopio óptico de las zonas deformadas, previa preparación metalográfica, nos ha permitido medir la variación en el tamaño de grano. Finalmente, se ha evaluado la influencia del grado de deformación en la resistencia a la corrosión del acero

Spin configuration of cylindrical bamboo-like magnetic nanowires

The surface and the internal magnetic structure of bamboo-like cylindrical nanowires with tailored diameter modulations have been determined exploiting the direct photoemission and transmission contrasts using photoemission electron microscopy combined with X-ray magnetic circular dichroism, as well as complementary magnetic force microscopy and micromagnetic simulations. Bamboo-like cylindrical nanowires with diameters of 130 and 140 nm, and a modulation periodicity of 400 nm were electrochemically grown into the pores of alumina templates. FeCoCu and Co nanowires were selected to offer parallel and perpendicular magnetization easy axis, respectively. For FeCoCu nanowires, a main longitudinal magnetization configuration is found consistent with the predominant shape anisotropy. In addition, a weaker modulated contrast along the wires' axis is observed that matches the position of each diameter modulation: vortex-like structures are observed at the ends of the wires and at the surface around the modulations. In Co nanowires, a multi-segmented vortex-like structure with alternating opposite chirality is found not matching the periodicity of the diameter modulations. Such a spin configuration is interpreted considering that Co nanowires exhibit hexagonal symmetry with c axis nearly perpendicular to the nanowires defining strong uniaxial transverse magnetocrystalline anisotropy.The study has been performed under the framework of the projects MAT2013-48054-C2-1-R and CSD2010-00024 supported by the MINECO from Spain. A.F.R. acknowledges financial support from the Spanish MICINN through the Ramón y Cajal Programme. J. A. F.-R. acknowledges financial support from MINECO and the European Social Fund through the “Ayudas para contratos predoctorales para la formación de doctores 2014”

Direct observation of transverse and vortex metastable magnetic domains in cylindrical nanowires

We present experimental evidence of transverse magnetic domains, previously observed only in nanostrips, in CoNi cylindrical nanowires with designed crystal symmetry and tailored magnetic anisotropy. The transverse domains are found together with more conventional vortex domains along the same cylindrical nanowire, denoting a bistable system with similar energies. The surface and the inner magnetization distribution in both types of domains are analyzed by photoemission electron microscopy with x-ray magnetic circular dichroism contrast, and hysteresis loop in individual nanowires are measured by magneto-optical Kerr effect. These experimental data are understood and compared with complementary micromagnetic simulations.The study has been performed under the framework of the Projects No. MAT2013-48054-C2-1-R, MAT2016-76824-C3-1-R, MAT-2015-68772-P, MAT2015-64110-C2-2-P supported by the MINECO from Spain and DURSI 2014SGR220 supported by the Catalan Government. J.A.F.-R. acknowledges financial support from MINECO and the ESF through the “Ayudas para contratos predoctorales para la formación de doctores 2014.