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Room-temperature magnetoelectric multiferroicity has been observed in c-axis oriented GaFeO$_3$ thin films (space group $Pna2_1$), grown on economic and technologically important (100)Si substrates by pulsed laser deposition technique. Structural analysis and comprehensive mapping of Ga:Fe ratio across a length scale range of 10$^4$ reveal coexistence of epitaxial and chemical strain. It induces formation of finer magnetic domains and large magnetoelectric coupling - decrease in remanent polarization by $\sim$21\% under $\sim$50 kOe. Magnetic force microscopy reveals presence of both finer ($<$100 nm) and coarser ($\sim$2 $\mu$m) magnetic domains. Strong multiferroicity in epitaxial GaFeO$_3$ thin films, grown on (100)Si substrate, brighten the prospect of their integration with Si-based electronics and could pave the way for development of economic and more efficient electromechanical, electrooptic or magnetoelectric sensor devices., Comment: 8 pages, 9 figures, accepted for publication in J. Appl. Phys

We report observation of surface-defect-induced room temperature multiferroicity - surface ferromagnetism ($M_S$ at 50 kOe $\sim$0.005 emu/g), ferroelectricity ($P_R$ $\sim$2 nC/cm$^2$), and significantly large magnetoelectric coupling (decrease in $P_R$ by $\sim$80\% under $\sim$15 kOe field) - in nanorods (diameter $\sim$100 nm) of double perovskite Y$_2$NiMnO$_6$ compound. In bulk form, this system exhibits multiferroicity only below its magnetic transition temperature $T_N$ $\approx$ 70 K. On the other hand, the oxygen vacancies, formed at the surface region (thickness $\sim$10 nm) of the nanorods, yield long-range magnetic order as well as ferroelectricity via Dzyloshinskii-Moriya exchange coupling interactions with strong Rashba spin-orbit coupling. Sharp drop in $P_R$ under magnetic field indicates strong cross-coupling between magnetism and ferroelectricity as well. Observation of room temperature magnetoelectric coupling in nanoscale for a compound which, in bulk form, exhibits multiferroicity only below 70 K underscores an alternative pathway for inducing magnetoelectric multiferroicity via surface defects and, thus, in line with magnetoelectric property observed, for example, in domain walls or boundaries or interfaces of heteroepitaxially grown thin films which do not exhibit such features in their bulk., Comment: 10 pages, 7 figures, published in Phys. Rev. B

In a nanocomposite of reduced graphene oxide (RGO) and BiFeO$_3$ (BFO), the remanent ferroelectric polarization is found to follow nonmonotonic magnetic field dependence at room temperature as the applied magnetic field is swept across 0-20 kOe on a pristine sample. The remanent ferroelectric polarization is determined both from direct electrical measurements on an assembly of nanoparticles and powder neutron diffraction patterns recorded under 0-20 kOe field. The nanosized ($\sim$20 nm) particles of BFO are anchored onto the graphene sheets of RGO via Fe-C bonds with concomitant rise in covalency in the Fe-O bonds. The field-dependent competition between the positive and negative magnetoelectric coupling arising from magnetostriction due to, respectively, interface and bulk magnetization appears to be giving rise to the observed nonmonotonic field dependence of polarization. The emergence of Fe-C bonds and consequent change in the magnetic and electronic structure of the interface region has influenced the coupling between ferroelectric and magnetic properties remarkably and thus creates a new way of tuning the magnetoelectric properties via reconstruction of interfaces in nanocomposites or heterostructures of graphene/single-phase-multiferroic systems., Comment: 10 pages, 12 figures, comments are welcome