Rheological properties of magnetic biogels

We report an experimental and theoretical study of the rheological properties of magnetic biogels consisting of fibrin polymer networks with embedded magnetite nanoparticles, swollen by aqueous solutions. We studied two types of magnetic biogels, differenced by the presence or absence of an applied magnetic field during the initial steps of cross-linking. The experiments demonstrated very strong dependence of the elastic modulus of the magnetic biogels on the concentration of the magnetic particles. We finally developed some theoretical models that explain the observed strong concentration effects.This study was supported by projects FIS2013-41821-R (Plan Nacional de Investigación Científica, Desarrollo e Innovación Tecnológica, MINECO, Spain, co-funded by ERDF, European Union) and FIS2017-85954-R (Ministerio de Economía, Industria y Competitividad, MINECO, andAgencia Estatal de Investigación, AEI, Spain, co-funded by Fondo Europeo de Desarrollo Regional, FEDER, European Union). A.Z. is grateful to the program of the Ministry of Education and Science of the Russian Federation, projects 02.A03.21.0006, 3.1438.2017/4.6, and 3.5214.2017/6.7, as well as to the Russian Fund of Basic Researches, project 18-08-00178

Study of GdCo/Si/Co/Si multilayers by polarized neutron reflectivity

In order to better understand the interesting magnetic behaviour found in the Rare Earth-transition metal/(spacer)/transition metal multilayers, a multilayer of Co/[Si/Gd0.36Co0.64/Si/Co]4/glass was studied by SQUID magnetic measurements and polarized neutron reflectivity. A model for the magnetic profile of the sample was proposed, which fitted well the polarized neutron reflectivity measurements at different magnetic states: ferrimagnetic/antiparallel state, under an applied field of 55 Oe, canted states (315 and 675 Oe) and saturation state (1700 Oe). It was found that even at the expected collinear states (ferrimagnet and saturation states), the magnetization was not totally collinear and there was a small component of the magnetization perpendicular to the applied field.Cajastur;FICYT;Gijon City Council;MICINN;Tekniker;University of Ovied