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L. J. Albornoz

Publications and source records attributed to L. J. Albornoz.

2 recordsLinked to original sources

Impact of growth conditions on the domain nucleation and domain wall propagation in Pt/Co/Pt stacks

Understanding the effect of fabrication conditions on domain wall motion in thin films with perpendicular magnetization is a mandatory issue in order to tune their properties aiming to design spintronics devices based on such phenomenon. In this context, the present work intends to show how different growth conditions may affect domain wall motion in the prototypical system Pt/Co/Pt. The trilayers were deposited by dc sputtering, and the parameters varied in this study were the Co thickness, the substrate roughness, and the base pressure in the deposition chamber. Magneto-optical Kerr effect-based magnetometry and microscopy combined with X-ray reflectometry, atomic force microscopy, and transmission electron microscopy were adopted as experimental techniques. This permitted us to elucidate the impact on the hysteresis loops and on the domain wall dynamics, produced by different growth conditions. As other authors, we found that Co thickness is strongly determinant for both the coercive field and the domain wall velocity. On the contrary, the topographic roughness of the substrate and the base pressure of the deposition chamber evidence a selective impact on the nucleation of magnetic domains and on domain wall propagation, respectively, providing a tool to tune these properties.

cond-mat.mtrl-sci

Entropy jump at the first-order vortex phase transition in Bi2Sr2CaCu2O8+δ with columnar defects

We study the entropy jump associated with the first-order vortex melting transition (FOT) in Bi2Sr2CaCu2O8+δ crystals by means of Hall probe magnetometry. The samples present a diluted distribution of columnar defects (CD) introduced by irradiation with Xe ions. The FOT is detected in ac transmittivity measurements as a paramagnetic peak, the height of which is proportional to the enthalpy difference entailed by the transition. By applying the Clausius-Clapeyron relation, we quantify the evolution of the entropy jump Δs as a function of the FOT temperature, TFOT, in both pristine crystals and crystals with CD. On increasing the density of CD, Δs decreases monotonically with respect to values found in pristine samples. The Δs versus TFOT dependence in the case of pristine samples follows reasonably well the theoretical prediction of dominant electromagnetic coupling for a model neglecting the effect of disorder. The data for samples with a diluted distribution of CD are not properly described by such a theoretical model.

cond-mat.supr-con