Observation of magnetoelectric coupling and local piezoresponse in modified (Na0.5Bi0.5)TiO3-BaTiO3-CoFe2O4 lead-free composites


Lead-free particulate multiferroic composites of [0.94(Na0.5Bi0.5)TiO3-0.06 BaTiO3]:(Co0.6Zn0.4)( Fe1.7Mn0.3)O-4 were synthesized and magnetoelectric (ME) properties were studied. X-ray diffraction and microstructural studies indicated the formation of a two-phase composite system without any impurities. The shift of Raman modes corresponding to ferroelectric and ferrite phases was assigned to the induced strain amid the formation of a two- phase system, in relation to the fraction of each phase in the samples. A strong local piezoresponse and hysteresis loops observed for composites established the ferroelectric properties at a nanoscale. Magnetostriction measurements revealed values of lambda(11) = -10.4 and lambda(12) = 5.3 ppm and piezomagnetic coefficient d lambda(11)/dH = -0.0087 ppm Oe(-1) at 0.45 kOe for a composite with a ferrite concentration of 35 mol%. A maximum change of 18.5% in magnetization after electrical poling indicates a strong magnetoelectric response of the present composites followed by a direct ME coefficient of 8.2 mV cm(-1) Oe(-1). Our studies point to the fact that the present multiferroic composites having strong ME coupling are useful for lead-free electronic applications.



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Ramana, EV; Figueiras, F; Graca, MPF; Valente, MA

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The authors would like to acknowledge the financial support from FCT, Portugal (SFRH/BPD/75582/2010).

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