Thickness dependence of the magnetoelectric coupling in Fe89Ga11 thin films deposited on ferroelectric PMN-PT single crystals

Abstract

We have investigated the effects of applying an electric field on the dc and ac magnetic response of Fe89Ga11 thin films (t = 6 , 11, 17, 22, and 28 nm) that have been deposited on ferroelectric PMN-PT (011) and (001) single crystals. Upon the application of an electric field we have observed that M vs. H hysteresis loops are modified in films grown on (011) crystals, consistent with a positive magnetostriction constant that depends on film thickness. From ferromagnetic resonance experiments at 9.5 GHz we obtained a thickness dependent magnetoelectric coefficient in the case of (011) substrates, showing a maximum dH dE / 150 Oe.m/MV fort = 28 nm, coincident with the estimations made from M vs. H loops. It was found that the direction of easy magnetization could be rotated by 90° upon the application of an electric field only in the case of 28 nm films deposited on PMN-PT (011). In thinner films the magnetoelectric coefficient is too small to overcome the magnetic anisotropy. These results indicate that if magnetostrictive materials are to be applied in straintronic devices the dependence of magnetic parameters with film thickness must be taken in account for optimum performance.