Multiferroic heterostructures of Fe3O4/PZT (lead zirconium titanate), Fe3O4/PMN‐PT (lead magnesium niobate‐lead titanate) and Fe3O4/PZN‐PT (lead zinc niobate‐lead titanate) are prepared by spin‐spray depositing Fe3O4 ferrite film on ferroelectric PZT, PMN‐PT and PZN‐PT substrates at a low temperature of 90 °C. Strong magnetoelectric coupling (ME) and giant microwave tunability are demonstrated by a electrostatic field induced magnetic anisotropic field change in these heterostructures. A high electrostatically tunable ferromagnetic resonance (FMR) field shift up to 600 Oe, corresponding to a large microwave ME coefficient of 67 Oe cm kV−1, is observed in Fe3O4/PMN‐PT heterostructures. A record‐high electrostatically tunable FMR field range of 860 Oe with a linewidth of 330–380 Oe is demonstrated in Fe3O4/PZN‐PT heterostructure, corresponding to a ME coefficient of 108 Oe cm kV−1. Static ME interaction is also investigated and a maximum electric field induced squareness ratio change of 40% is observed in Fe3O4/PZN‐PT. In addition, a new concept that the external magnetic orientation and the electric field cooperate to determine microwave magnetic tunability is brought forth to significantly enhance the microwave tunable range up to 1000 Oe. These low temperature synthesized multiferroic heterostructures exhibiting giant electrostatically induced tunable magnetic resonance field at microwave frequencies provide great opportunities for electrostatically tunable microwave multiferroic devices.

No abstract

A facile template-free method has been developed for the controllable fabrication of novel hierarchical flower-like Bi 2 MoO 6 hollow spheres via a solvothermal process in the presence of ethylene glycol. The formation mechanism was proposed based on the evolution of morphology as a function of solvothermal time, which involves the initial formation of nanoparticles followed by their selfaggregation to microspheres and transformation into hierarchical flower-like hollow spheres by Ostwald ripening. The integer appearance of the hierarchical flower-like Bi 2 MoO 6 hollow spheres was maintained after calcination at 400 C for 3 h. Furthermore, the calcined hierarchical flower-like Bi 2 MoO 6 hollow spheres exhibited excellent visible-light-driven photocatalytic efficiency for the degradation of Rhodamine B, up to 95% within 2 h, which was much higher than that of Bi 2 MoO 6 prepared by solid-state reaction and TiO 2 (P25). The improved photocatalytic performance could be ascribed to the special hierarchical hollow sphere structure, good permeability and large surface area.

We demonstrate a semiconducting material, TiO 2−δ , with ferromagnetism up to 880 K, without the introduction of magnetic ions. The magnetism in these films stems from the controlled introduction of anion defects from both the filmsubstrate interface as well as processing under an oxygen-deficient atmosphere. The room-temperature carriers are n-type with n ∼ 3 × 10 17 cm −3 . The density of spins is ∼10 21 cm −3 . Magnetism scales with conductivity, suggesting that a double exchange interaction is active. This represents a new approach in the design and refinement of magnetic semiconductor materials for spintronics device applications.(Some figures in this article are in colour only in the electronic version)Recent research efforts on the growth of magnetically ordered semiconductor materials [1,2] have received great attention because of potential new applications in spintronics devices [3]. The rationale for this optimism is the plausibility of integrating properties of both magnetic and semiconductor materials in new devices [1] (e.g. spin diodes [3-6] and spin-FETs [7]). Recent research has focused on dilute magnetic semiconductors (DMS) which were synthesized by introducing magnetic ions (e.g. Mn, Co, Fe, and etc) into conventional III-V [1, 2] and II-VI type semiconductors [8,9] or wide bandgap semiconductors including ZnO and TiO 2 [8][9][10][11][12][13]. Also, ferromagnetism was induced in films of hafnium dioxide, HfO 2 , deposited by pulsed laser deposition (PLD) on sapphire substrates and attributed to defect doping [10][11][12]. Bulk HfO 2 is intrinsically non-magnetic and electrically insulating. This report has created intense