Magnetoelectric nano-Fe3O4∕CoFe2O4∥PbZr0.53Ti0.47O3 composite

Abstract

A new magnetoelectric hybrid device composed of a nanoparticulate magnetostrictive iron oxide-cobalt ferrite film on a piezoelectric lead zirconic titanate crystal serving as both substrate and straining medium is described. Nano-Fe 3 O 4 / CoFe 2 O 4 particles, ranging from 5 to 42 nm, were prepared using a variation of the sol-gel method. A small electric field, 5 -10 kV cm −1 , applied at the coercive field of the nano-Fe 3 O 4 / CoFe 2 O 4 component modulates the film magnetization up to 10% of the saturation magnetization of ferrite. At the smallest particle size of 5 nm, the coercive field is as low as 25 Oe and the inverse ME E voltage coefficient is as high as ͑10.1 V / cm Oe͒ −1 . © 2008 American Institute of Physics. ͓DOI: 10.1063/1.2841064͔The recent surge of papers describing magnetoelectric composites ͑MECs͒ may be divided into two groups; the first consisting of papers reporting on metal-oxide composites and the second containing those publications dealing with oxide-oxide structures. High MEC susceptibilities at low magnetic fields are achieved with metal-oxide MECs by choosing either glassy metals or designing highly magnetostrictive metallic components with zero demagnetization factor. 1,2 Similar approaches are not as readily accessible for oxide/oxide ME composites as these are predominantly fabricated by thin film technologies, e.g., 3 and the oxide featuring the highest magnetostriction, CoFe 2 O 4 ͑CFO͒, possesses a large magnetocrystalline anisotropy. The fully epitaxial self-assembled 3-1 CFO/BaTiO 3 ME composites 4 represent somewhat of an exception. Therefore, in an effort to reduce the effective magnetocrystalline anisotropy and thereby the coercive force of CFO, we developed a nanoFe 3 O 4 / CoFe 2 O 4 ʈ lead zirconic titanate ͑PZT͒ MEC, whose fabrication and properties are described in the following.To achieve a highly effective magnetoelectric signal, ME composites require high piezoelectric and magnetic susceptibilities. 5,6 Pb͑Zr 0.53 Ti 0.47 ͒O 3 is a well-understood piezoelectric material fulfilling this requirement. Ferromagnetic bulk Co ferrite is a good choice due to its high magnetostriction. However, because of its high magnetocrystalline anisotropy, 7 it has a low magnetostrictive initial susceptibility that results in a low magnetoelectric susceptibility d / dH. In nanoparticles, the effective magnetocrystalline anisotropy is lowered and d / dH can be increased while maintaining its high saturation 8 as has also been demonstrated for Co ferrite. 9 Therefore, in order to create an all-oxide MEC with a large ME coupling coefficient, a nanoFe 3 O 4 / CoFe 2 O 4 / Pb͑Zr 0.53 Ti 0.47 ͒O 3 was developed. This composite yields giant ME voltages under significantly lower magnetic bias fields than previously reported for CFO/PZT MECs. 10 Its manufacture and properties will be described next.The composite was manufactured by spinning a CFO sol-gel 11 onto a mirror polished PZT single crystal substrate, obtained from Fuji Ceramics, Inc. The deposition technique and substrate were ch...

Recent Progress in Multiferroic Magnetoelectric Composites: from Bulk to Thin Films

“…Traditionally, piezoelectric effect is an effi cient way to convent motion to electricity, [ 85 ] which has been designed and cooperated in some real systems, such as fi lms or textured fi lms with preferential orientation, and provide fl exibility to obtain thick fi lms with large areas. [112][113][114][115][116][117][118][119][120] However, when the growth of oxide thin fi lms with high structural perfection and the ability to customize oxide layering down to the atomic layer level are demanded, the traditional chemical methods are not applicable. Alternatively, the vapor deposition techniques (e.g., PLD, MBE, and sputtering) have the ability of yielding excellent epitaxial growth of thin fi lms with atomicscale thickness control and coherent interfaces.…”

Electrical control of magnetism in oxides

“…The electronic phase transition driven by strain under electric field is supported by works using LSMO, [17,18] LCMO, [39] and Pr 0.6 Ca 0.4 MnO 3 [40] with strong tendency toward phase separation as ferromagnetic layer. On the contrary, the changes of magnetic anisotropy under electric field was widely accepted in CoFe 2 O 4 [41,42] and Fe 3 O 4 , [43][44][45] where a magnetization orientation shift of 17° in Fe 3 O 4 /BaTiO 3 was observed.…”

“…BTO, PMN-PT, and PZT). [17,18,[39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58] The external electric field alters the lattice or shape of the ferroelectric crystal by the converse piezoelectric effect, and then transfers the strain to the proximate magnetic layer, leading to the changes in magnetic anisotropy, magnetization rotation, and coercivity through the magnetostriction. In the FM/FE heterostructures, both (anti-)ferromagnetic oxides and metals are controlled by electric field.…”

Nanolamellar magnetoelectric BaTiO3–CoFe2O4 bicrystal

“…[4][5][6] We used this approach to improve on previous eutectoid 7 and other [8][9][10][11] syntheses of CFO/BTO composites. Avellaneda and Harshe 12 already demonstrated that solidification of eutectic BTO-CFO leads to lamellar microstructures.…”