Infrared and magnetic characterization of the multiferroic Bi2FeCrO6 thin films in a broad temperature range

Infrared reflectance spectra of an epitaxial Bi2FeCrO6 thin film prepared by pulsed laser deposition on LaAlO3 substrate were recorded between 10 and 900 K. No evidence for a phase transition to the paraelectric phase was observed, but some phonon anomalies were revealed near 600 K. Most of the polar modes exhibit only a gradual softening, which results in a continuous increase of the static permittivity on heating. It indicates that the ferroelectric phase transition should occur somewhere above 900 K. Magnetic measurements performed up to 1000 K, revealed a possible magnetic phase transition between 600 and 800 K, but the exact critical temperature cannot be determined due to a strong diamagnetic signal from the substrate. Nevertheless, our experimental data show that the B-site ordered Bi2FeCrO6 is one of the rare high-temperature multiferroics.Comment: subm. to PR

ANISOTROPY AND RELAXATION IN MANGANESE RICH MANGANESE FERRITES

Des mesures de résonance ferromagnétique ont été réalisées sur des échantillons monocristallins de ferrite de manganèse MnxFe3-xO4 avec x = 1,013 et x = 1,46 dans la gamme de température de l'hélium liquide jusqu'à la température ambiante. Pour l'échantillon x = 1,46 la dépendance angulaire du champ de résonance a été mesurée dans le plan (110) à des températures de 2 °K, 4,2 °K et 77 °K. La variation de la largeur de raie en fonction de la température présente un maximum à approximativement 10 °K, en accord avec des études antérieures. La dépendance angulaire de la largeur de raie au voisinage de ce maximum est en accord avec l'hypothèse d'une configuration de spins inclinés dans le sous-réseau octaédrique de structure spinelle.Measurements of ferromagnetic resonance were performed on single crystal samples of manganese ferrites MnxFe3-xO4 with x = 1.013 and x = 1.46 in the temperature range from liquid helium up to room temperatures. For the sample x = 1.46 the angular dependence of the resonance field was measured in (110) plane at temperatures 2 °K, 4.2 °K and 77 °K. The temperature dependence of linewidth displays a maximum at approximately 10 °K in agreement with earlier studies. The angular dependence of linewidth in the vicinity of this maximum is consistent with the assumption of canted spin configurations in the octahedral sublattice of the spinel structure

Fe2O3/SiO2Fe_2O_3/SiO_2 Hybrid Nanocomposites Studied Mainly by Mössbauer Spectroscopy

Magnetic nanocomposites exhibit promising applications in many areas, for example optics, electronics, biology, medicine, etc. The main goal of this study was to synthesize magnetic ε-$Fe_2O_3$ nanoparticles embedded in amorphous $SiO_2$. These materials were prepared by the help of ultrasonic activation and subsequent annealing in nitrogen atmosphere or air with concentrations of iron oxide of about 20 and 30 wt.%. The structure and properties of the final product were analysed by the Mössbauer spectrometry as well as by X-ray diffraction, scanning electron microscopy, and high resolution transmission electron microscopy. They strongly depend on the initial conditions of preparation

INHOMOGENEOUS MAGNETIZATION IN AMORPHOUS Ni-Fe BASED ALLOYS

No abstract availabl

Fe 2

Magnetic nanocomposites exhibit promising applications in many areas, for example optics, electronics, biology, medicine, etc. The main goal of this study was to synthesize magnetic ε-$Fe_2O_3$ nanoparticles embedded in amorphous $SiO_2$. These materials were prepared by the help of ultrasonic activation and subsequent annealing in nitrogen atmosphere or air with concentrations of iron oxide of about 20 and 30 wt.%. The structure and properties of the final product were analysed by the Mössbauer spectrometry as well as by X-ray diffraction, scanning electron microscopy, and high resolution transmission electron microscopy. They strongly depend on the initial conditions of preparation

Mössbauer studies of magnetic Fe2O3/SiO2 nanocomposites

Suppl. E (2006): Proceedings of the International Colloquium "Mössbauer Spectroscopy in Materials Science" (June 11–15, 2006, Kočovce, Slovak Republic)A large variety of glass and glass ceramics may be obtained by sol-gel process from hydrolysis of tetraethoxysilane. The transformation involves hydrolysis and polycondensation reactions leading to the growth of clusters that eventually collide together to form a gel. The structure and properties of the final product have been found to be strongly dependent on the initial conditions of preparation. Silica nanocomposites based on Fe2O3/SiO2 were prepared with the help of ultrasonic activation and subsequent annealing in nitrogen atmosphere or air with concentrations of iron oxide of about 20 to 30wt.%