We report growth of various phase architectures of self-assembled BiFeO3-CoFe2O4 (BFO-CFO) thin films on differently oriented SrTiO3 (STO) substrates. CFO forms segregated square, stripe, and triangular nanopillars embedded in a coherent BFO matrix on (001)-, (110)-, and (111)-oriented STO substrates, respectively. Nanostructures with an aspect ratio of up to 5:1 with a prominent magnetic anisotropy were obtained on both (001) and (110) STO along out-of-plane and in-plane directions. Magnetic easy axis rotation from in-plane to out-of-plane directions was realized through aspect ratio control. An intractable in-plane anisotropy was fixed in CFO on (111) STO due to the triangular shape of the ferromagnetic phase nanopillars. These studies established a detailed relationship of magnetic anisotropy with specific shape and dimensions of ordered magnetic arrays. The results suggest a way to effectively control the magnetic anisotropy in patterned ferromagnetic oxide arrays with tunable shape, aspect ratio, and elastic strain conditions of the nanostructures.

; et al., "Giant electric field controlled magnetic anisotropy in epitaxial BiFeO3-CoFe2O4 thin film heterostructures on single crystal Pb(Mg1/3Nb2/3)(0.7)Ti0.3O3 substrate," Appl. Phys. Lett. 99, 043110 (2011); http://dx

Ion doping effects in multiferroic MnWO4 J. Appl. Phys. 111, 083906 (2012) Origin of ferromagnetism and oxygen-vacancy ordering induced cross-controlled magnetoelectric effects at room temperature J. Appl. Phys. 111, 073904 (2012) Synthesis and signature of M-E coupling in novel self-assembled CaCu3Ti4O12-NiFe2O4 nanocomposite structure J. Appl. Phys. 111, 074302 (2012) Quantum levitation of a thin magnetodielectric plate on a metallic plate using the repulsive Casimir force J. Appl. Phys. 111, 074304 (2012) Additional information on J. Appl. Phys. The present work shows good control of both magnetic and electric properties with electric and magnetic fields, respectively, for epitaxial CoFe 2 O 4 (CFO) films on Pb(Mg,Nb)O 3 -PbTiO 3 (PMN-PT). X-ray reciprocal space mapping revealed a transformation between a-and c-domains in the PMN-PT under electric field (E). Magnetic hysteresis loop and magnetic force microscopy (MFM) measurements showed a considerable change in the magnetic properties in specific areas of CFO layers poled by MFM probe tips. Furthermore, a pulsed electric field applied to the substrate was found to switch the magnetization of CFO between high and low values, depending on the polarity of E.

We have deposited self-assembled BiFeO3-CoFe2O4 (BFO-CFO) thin films on (100)-oriented SrRuO3-buffered Pb(Mg1/3Nb2/3)0.62Ti0.38O3 (PMN-38PT) single crystal substrates. These heterostructures were used for the study of real-time changes in the magnetization with applied DC electric field (EDC). With increasing EDC, a giant magnetization change was observed along the out-of-plane (easy) axis. The induced magnetization changes of the CFO nanopillars in the BFO/CFO layer were about ΔM/MrDC = 93% at EDC = −3 kv/cm. A giant converse magnetoelectric (CME) coefficient of 1.3 × 10−7 s/m was estimated from the data. By changing EDC, we found multiple(N ≥ 4) unique possible values of a stable magnetization with memory on the removal of the field.

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Articles you may be interested inThe effects of interface misfit strain and surface tension on magnetoelectric effects in layered magnetostrictivepiezoelectric composites J. Appl. Phys. 114, 044109 (2013) In this paper, we discuss a theoretical model with experimental verification for the resonance enhancement of magnetoelectric (ME) interactions at frequencies corresponding to bending-tension oscillations. A dynamic theory of arbitrary laminated magneto-elasto-electric bars was constructed. The model included bending and longitudinal vibration effects for predicting ME coefficients in laminate bar composite structures consisting of magnetostrictive, piezoelectric, and pure elastic layers. The thickness dependence of stress, strain, and magnetic and electric fields within a sample are taken into account, as such the bending deformations should be considered in an applied magnetic or electric field. The frequency dependence of the ME voltage coefficients has obtained by solving electrostatic, magnetostatic, and elastodynamic equations. We consider boundary conditions corresponding to free vibrations at both ends. As a demonstration, our theory for multilayer ME composites was then applied to ferromagnetic-ferroelectric bilayers, specifically Metglas-PZT ones. A theoretical model is presented for static (low-frequency) ME effects in such bilayers. We also performed experiments for these Metglas-PZT bilayers and analyzed the influence of Metglas geometry (length and thickness) and Metglas/PZT volume fraction on the ME coefficient. The frequency dependence of the ME coefficient is also presented for different geometries (length, thickness) of Metglas. The theory shows good agreement with experimental data, even near the resonance frequency. V C 2012 American Institute of Physics.[http://dx

Using conventional methods to synthesize magnetic nanoparticles (NPs) with uniform size is a challenging task. Moreover, the degradation of magnetic NPs is an obstacle to practical applications. The fabrication of silica‐shielded magnetite NPs on carbon nitride nanotubes (CNNTs) provides a possible route to overcome these problems. While the nitrogen atoms of CNNTs provide selective nucleation sites for NPs of a particular size, the silica layer protects the NPs from oxidation. The morphology and crystal structure of NP–CNNT hybrid material is investigated by transmission electron microscopy (TEM) and X‐ray diffraction. In addition, the atomic nature of the N atoms in the NP–CNNT system is studied by near‐edge X‐ray absorption fine structure spectroscopy (nitrogen K‐edge) and calculations of the partial density of states based on first principles. The structure of the silica‐shielded NP–CNNT system is analyzed by TEM and energy dispersive X‐ray spectroscopy mapping, and their magnetism is measured by vibrating sample and superconducting quantum interference device magnetometers. The silica shielding helps maintain the superparamagnetism of the NPs; without the silica layer, the magnetic properties of NP–CNNT materials significantly degrade over time.

We investigate the origin of in-plane uniaxial magnetic anisotropy of epitaxial ferromagnetic MnAs film on GaAs(001). Interestingly, as temperature increases, the in-plane uniaxial magnetic anisotropy along the MnAs[112¯0] direction changes and then disappears. Direct microscopic domain observations show that the type of domain structure changes from a simple domain to a closure one with increasing temperature. From these results, the temperature-dependent change of the in-plane magnetic anisotropy is ascribed to a decrease in the shape anisotropy induced by the decrease in the width of the ferromagnetic α-stripe.