Microstructure and magnetic properties of BiMnO3 and BiFe0.5Mn0.5O3 films, prepared by rf magnetron sputtering on LaAlO3 (001) single-crystalline substrate, are investigated. The selected-area electron diffraction analysis allows us to identify the crystal structure of the BiMnO3 film as orthorhombic, while the BiFe0.5Mn0.5O3 film has a hexagonal lattice symmetry. High-resolution electron microscopy study reveals the presence of strip-domain phase with a periodic spacing of about 3c in both films. Magnetic measurements show that in addition to the basic paramagnetic phase the films exhibit Griffiths phase behavior in a wide temperature range. We argue that the observed weak ferromagnetism is due to the strip-domain layered inclusions, rather than intrinsic physical origin of the films.@en

Magnetotransport properties of the Pr0.5Ca0.5MnO3/La0.7Sr0.3MnO3 bilayer and the Pr0.5Ca0.5MnO3 and La0.7Sr0.3MnO3 films deposited on LaAlO3 (001) substrate by pulse laser deposition were investigated. X-ray diffraction and high-resolution electron-microscopy analysis reveal that lattice parameters for the constituent sublayers in the bilayer are very close to those for the individual films. It was found that a ferromagnetic transition in the La0.7Sr0.3MnO3 sublayer significantly modifies magnetotransport properties of the Pr0.5Ca0.5MnO3 constituent sublayer due to the magnetic proximity effect. Evidence of this effect includes the appearance of exchange bias interaction between the constituent sublayers, a localized-to-itinerant crossover in the system of polarized electrons, which results in formation of the Griffiths-like ferromagnetic state, and an unusual polar transport of carriers. Experimental results were analyzed within the framework of the modern theoretical approac@en

This paper proposes an efficient current control algorithm and a suitable power conversion system of a multiple-module transverse flux permanent magnet generator (MM-TFPMG) for large-scale direct-drive wind turbines. The MM-TFPMG is composed of multiple-module structures based on an independent three-phase configuration. In this paper, the single-phase current control applying the d-q transformation and the independent three-phase dqn-axes current control are proposed for the generator-side control of the MM-TFPMG. The control performance and characteristics of the single-phase dq-axes current control with a variable cutoff frequency and the independent three-phase dqn-axes current control using a concept of vector control are analyzed. As a result, the independent three-phase dqn-axes current control by using the vector control is an appropriate method to efficiently control the generator-side of the MM-TFPMG. The proposed algorithm is easily implemented and has less computation resource. Moreover, the control performance is better than the independent single-phase dq-axes current control despite the change of wind speed. The validity and usefulness of the proposed independent three-phase dqn-axes current control algorithm are verified and compared through several experimental results.@en

Nd(0.52)Sr(0.48)MnO(3) films of various thicknesses have been prepared by dc magnetron sputtering on single crystal LaAlO(3) (001) substrates. Reducing the film thickness leads to a significant suppression of ferromagnetic (FM) ordering and the Curie point falls below the antiferromagnetic (AFM) transition temperature. When this occurs, a huge rise of the magnetoresistance ratio from 400 to 60 000% is observed in an applied magnetic field of 5 T. We surmise that this new kind of the enhanced colossal magnetoresistance effect originates in the FM/AFM competition and the collapse of the charge-ordered state at high magnetic fields, rather than in the regular double-exchange mechanism.@en

-ray diffraction analysis and high-resolution electron microscopy of BiFeO(3) films prepared by dc magnetron sputtering on single-crystal LaAlO(3) (001) substrates reveal that the films have a highly c-oriented orthorhombic crystalline structure. The magnetic properties of the BiFeO3 films are typical of ensembles of interacting superparamagnetic clusters, rather than Dzyaloshinskii-Moriya weak ferromagnets. The appearance of extrinsic nanoscale superparamagnetic clusters is explained by an oxygen deficiency in certain regions of the film, where ferromagnetic ordering can be realized through a double-exchange Zener mechanism.@en