Experimental realization
of thin films with a significant
room-temperature
magnetoelectric coupling coefficient,αME, in the absence of an external DC magnetic field, has been
thus far elusive. Here, a large coupling coefficient of 750 ±
30 mV Oe–1cm–1is reported for
multiferroic polymer nanocomposites (MPCs) thin-films in the absence
of an external DC magnetic field. The MPCs are based on PMMA-grafted
cobalt-ferrite nanoparticles uniformly dispersed in the piezoelectric
polymer poly(vinylidene fluoride-co-trifluoroethylene,
P(VDF-TrFE). It is shown that nanoparticle agglomeration plays a detrimental
role and significantly reducesαME. Surface functionalization of the nanoparticles by grafting a layer
of poly(methyl methacrylate) (PMMA)viaatom transfer
radical polymerization (ATRP) renders the nanoparticle miscible with
P(VDF-TRFE) matrix, thus enabling their uniform dispersion in the
matrix even in submicrometer thin films. Uniform dispersion yields
maximized interfacial interactions between the ferromagnetic nanoparticles
and the piezoelectric polymer matrix leading to the experimental demonstration
of largeαMEvalues in solution-processed
thin films, which can be exploited in flexible and printable multiferroic
electronic devices for sensing and memory applications.