Anisotropic Magnetoresistivity in Structured Elastomer Composites: Modelling and Experiments

MIETTA, J.L.; TAMBORENEA, PABLO; NEGRI, RICARDO MARTÍN

SOFT MATTER

ROYAL SOC CHEMISTRY

Lugar: CAMBRIDGE; Año: 2016 vol. 12 p. 6430 - 6441

1744-683X

A constitutive model for the anisotropic magnetoresistivity in structured elastomer composites (SECs) isproposed. The SECs considered here are oriented pseudo-chains of conductive-magnetic inorganic materialsinside an elastomer organic matrix. The pseudo-chains are formed by fillers which are simultaneouslyconductive and magnetic dispersed in the polymer before curing or solvent evaporation. The SEC is thenprepared in the presence of a uniform magnetic field, referred to as Hcuring. This procedure generates thepseudo-chains, which are preferentially aligned in the direction of Hcuring. Electrical conduction ispresent in that direction only. The constitutive model for the magnetoresistance considers the magneticpressure, Pmag, induced on the pseudo-chains by an external magnetic field, H, applied in the directionof the pseudo-chains. The relative changes in conductivity as a function of H are calculated byevaluating the relative increase of the electron tunnelling probability with Pmag, a magneto-elasticcoupling which produces an increase of conductivity with magnetization. The model is used to adjustexperimental results of magnetoresistance in a specific SEC where the polymer is polydimethylsiloxane,PDMS, and fillers are microparticles of magnetite?silver (referred to as Fe3O4[Ag]). Simulations of theexpected response for other materials in both superparamagnetic and blocked magnetic states are presented,showing the influence of the Young?s modulus of the matrix and filler?s saturation magnetization.