Eur. Phys. J. B 76, 399-404 (2010)
https://doi.org/10.1140/epjb/e2010-00225-0

Electrical relaxation induced by magnetostriction in a MEMS device

Architecture integrating a Co submillimetric pattern of submicrometric holes and a polymeric amplifying layer

¹ Physics Department, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Turin, Italy
² Materials Science and Chemical Engineering Department, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Turin, Italy

Corresponding author: ^a alessandro.chiolerio@polito.it

Received: 28 January 2010
Revised: 9 June 2010
Published online: 16 July 2010

Abstract

Electrical resistance relaxation measurements were performed on a regular array of Co magnetic antidots submitted to a magnetic field, using a thin Cu film with bone-like shape positioned across the pattern; the introduction of a thin resist layer spin-coated on the Cu bridge before the deposition of the external leads introduced a hopping-dominated path for injected currents, controlled by the barrier thickness. The in-plane magnetic field generated by an electromagnet was switched between 0 and 3.5 kOe (fully saturated Co) and kept constant while the resistance was continuously monitored under steady current injection. A strong, unsaturating resistance variation with time after field switching was measured, corresponding to a resistance decrease greater than 20% after tents of ks. When the field was switched from 3.5 kOe back to zero the measured resistance displayed a corresponding positive variation. The two effects were repeatedly observed by subsequently cycling the magnetic field. Electron microscopy analysis showed that a peculiar dendritic structure had developed in the polymeric resist, consisting of mass density oscillations whose principal arms were oriented roughly at 45° with respect to the current density vector, possibly because of the mechanical stress induced by magnetostriction of Co antidots. A detailed analysis showed that mass density fluctuations within dendritic structures may be correlated with specific perturbation events observed in the electrical resistance relaxation during the measurements.