IOP PUBLISHING JOURNAL OF PHYSICS D: APPLIED PHYSICS J. Phys. D: Appl. Phys. 42 (2009) 045007 (5pp) doi:10.1088/0022-3727/42/4/045007 Strong magnetoelectric coupling in ferrite/ferroelectric multiferroic heterostructures derived by low temperature spin-spray deposition M Liu 1 , O Obi 1 , J Lou 1 , S Stoute 1 , Z Cai 2 , K Ziemer 2 and N X Sun 1,3 1 Department of Electrical and Computer Engineering, Northeastern University, Boston, MA 02115, USA 2 Department of Chemical Engineering, Northeastern University, Boston, MA 02115, USA E-mail: nian@ece.neu.edu (N X Sun) Received 7 December 2008, in final form 24 December 2008 Published 30 January 2009 Online at stacks.iop.org/JPhysD/42/045007 Abstract Strong magnetoelectric (ME) interaction was demonstrated at both dc and microwave frequencies in a novel Zn 0.1 Fe 2.9 O 4 /PMN–PT (lead magnesium niobate–lead titanate) multiferroic heterostructure, which was prepared by spin-spray depositing a Zn 0.1 Fe 2.9 O 4 film on a single-crystal PMN–PT substrate at a low temperature of 90 ◦ C. A large electric-field induced ferromagnetic resonance field shift up to 140 Oe was observed, corresponding to an ME coefficient of 23 Oe cm kV −1 . In addition, a large electrostatic field tuning of the magnetic hysteresis loops was observed with a large squareness ratio change of 18%. The spin-spray deposited ferrite/piezoelectric multiferroic heterostructures exhibiting strong ME interactions at both dc and microwave frequencies provide great opportunities for novel electrostatically tunable microwave magnetic devices synthesized at a low temperature. (Some figures in this article are in colour only in the electronic version) 1. Introduction Magnetization tuning in many microwave magnetic devices is performed by external magnetic fields generated by electromagnets, which is slow, bulky, noisy and energy consuming [1]. Recently, multiferroic composite materials with two constituent phases of ferro/ferrimagnetic phase and ferroelectric phase have attracted an increasing amount of interest due to their potential applications in many multifunctional devices [2–12]. Such materials can display a large stress/strain mediated magnetoelectric (ME) effect, i.e. a dielectric polarization variation as a response to an applied magnetic field or an induced magnetization by an external electric field. To achieve a large stress mediated ME coupling, strong adhesion between two constituent multiferroic phases and a small clamping effect from the substrate are essential. For a nano-multiferroic composite, core–shell nanowires or nanotube structures are good candidates for realization of 3 Author to whom any correspondence should be addressed. large ME coupling due to their large interface area and their small clamping effect by removing the support core [13, 14]; for a laminate multiferroic heterostructure, strong adhesion and a large volume ratio are necessary to guarantee 100% deformation transmission and achieve large ME coupling which could enable many device applications, such as pico- tesla magnetometers, filters, resonators and phase shifters [12, 15–17]. More recently, we have reported a new class of metallic FeGaB films derived by magnetron sputtering, which showed a record high tunable ferromagnetic resonance (FMR) frequency of 900 MHz or 58% in FeGaB/Si/PMN–PT multiferroic composites [18, 19]. However, the corresponding electrostatically induced effective magnetic field is still relatively low of ∼30 Oe in the FeGaB film, which is also comparable to what has been reported by other groups [15–17]. New multiferroic composite materials are needed in order to achieve higher electrostatically induced effective magnetic fields which are critical for many microwave devices. The spin-spray deposition process is a wet chemical synthesis technique involving several chemical reactions for 0022-3727/09/045007+05$30.00 1 © 2009 IOP Publishing Ltd Printed in the UK