Hyperfine fields and magnetoelastic surface effects in Fe72Cu1.5Nb4Si13.5B9 nanocrystalline alloy

In this work hyperfine fields of two-phase nanocrystalline Fe72Cu1.5Nb4Si13.5B9 alloys were studied in order to verify the existence of surface effects. To obtain a series of nanocrystalline samples with small grains of different sizes, a special non- -isothermal annealing procedure of an initially amorphous ribbon was applied. In the case of samples with a significant amount of crystallites, a high field (about 27.5 T) component of continuous part of the hyperfine field distribution was found that could be attributed to boundary regions between the grains and rest of the sample. The existence of the surface effects was confirmed in the magnetostrictive experimen

Surface Effects in Fe-Based Nanocrystalline Alloys

The microstructural and Mossbauer investigations of FeZrBCu nanocrystalline alloy are presented. The results obtained indicate that fine bcc-Fe grains do possess identifiable surface properties which arise from the symmetry restriction at grain boundary

EXAFS analysis of grain boundaries in nanocrystalline Fe85Zr7B6Cu2\mathrm{Fe_{85}Zr_7B_6Cu_2} alloys

Nanocrystalline Fe85Zr7B6Cu2 alloys were obtained from the formerly amorphous Fe85Zr7B6Cu2 alloy by a heat treatment at several temperatures ranging from 480°C to 600°C. The ultrafine nanocrystalline structure of bcc-Fe grains with a grain size of 3–15 nm diameter embedded in an amorphous matrix was established using transmission electron microscopy. X-ray absorption spectra at the Fe K-edge for Fe85Zr7B6Cu2 amorphous and nanocrystalline alloys and metallic Fe foil were measured using synchrotron radiation.Fourier analysis of extended X-ray absorption fine structure (EXAFS) for alloys was performed and two models of grain boundaries in nanocrystalline Fe85Zr7B6Cu2 alloys were proposed. The heat treatment of alloys at temperatures of 480°C and 500°C creates simple boundaries between crystalline grains and amorphous matrix, while the heat treatment at higher temperatures from 540°C to 600°C can produce boundaries in the form of Fe-free interfaces with thickness of about 0.3 nm. A model of an Fe-free interface being a barrier for grain growth can explain the nanocrystallization phenomenon of Fe85Zr7B6Cu2 alloys

Magnetic Properties of Ferrofluid with Cobalt Ferrite Particles

Low temperature Mössbauer investigations of a diluted magnetic fluid containing ultrafine CoFe$\text{}_{2}$O$\text{}_{4}$ particles are presented. The thermal evolution of cobalt ferrite particles from the magnetically ordered state to the superparamagnetic state with the blocking temperature at about 80 K, is shown

X-Ray Absorption Studies of Fe73.5\text{}_{73.5}Cu1\text{}_{1}Nb3\text{}_{3}Si15.5\text{}_{15.5}B7\text{}_{7} Amorphous and Nanocrystalline Alloys

The nanocrystalline state of the formally amorphous alloy Fe$\text{}_{73.5}$Cu$\text{}_{1}$Nb$\text{}_{3}$Si$\text{}_{15.5}$B$\text{}_{7}$ is achieved by a heat treatment at temperatures between 500°C and 600°C. The XANES and EXAFS methods were applied for investigation of local structure and chemical bonding around Fe atoms in amorphous and nanocrystalline alloys. The Fe K absorption spectra were measured in the transmission mode at room temperature for Fe$\text{}_{73.5}$Cu$\text{}_{1}$Nb$\text{}_{3}$Si$\text{}_{15.5}$B$\text{}_{7}$ amorphous and nanocrystalline alloys and compared with the spectra for Fe metallic foil and Fe$\text{}_{3}$Si polycrystalline samples

Effect of Surfaces of FeNbCuBSiP Ribbons

Boron was partially substituted by phosphorus (3 at.%) in two Si-poor Fe-Nb-Cu-B-Si Finemets. Mostly non-significant changes were observed after vacuum annealing at 500°C, whereas equivalent Ar annealing resulted in significantly better soft-magnetic properties, which suffer from compressive surfaces stress. Possibly by hampering surface crystallization, the substitution eased the surfaces stress and reduced undesired off-axis anisotrophy at the cost of limiting the useful annealing temperature

Accents in Modern High Saturation Nanocrystalline Fe-Rich Alloys

Post processing limits for iron-rich Fe-Cu-Si-B-P high-induction rapidly-quenched ribbons have been tested. 530°C/20 min is already too much, formed borides being the essential culprit of magnetic properties deterioration. Unlike standard Si-poor Fe-Nb-Cu-B-Si Finemets, these alloys annealed even in "technical" Ar below the upper limit do not create significant squeezing surfaces

Structure and Magnetic Proporties of Polymer Matrix Nanocomposites

Structure and magnetic properties of the thermal decomposition products of Fe(III)Co(II) acrylate complex were analysed. The crystalline phases, which were found in the fully processed material, at 643 K, were Fe$\text{}_{3}$O$\text{}_{4}$, CoFe$\text{}_{2}$O$\text{}_{4}$, and CoO and had a mean particle size of about 30 nm. In the intermediate stages of the thermolysis iron was present in a form of Fe$\text{}^{III}$ (trivalent low-spin iron), Fe$\text{}^{2+}$ (divalent high-spin iron), and Fe$\text{}_{3}$O$\text{}_{4}$. The coercivity and remanence were measured versus temperature in the range of 5-300 K, in 1.1 T applied field. Both, $\text{}_{M}$H$\text{}_{c}$ and M$\text{}_{r}$, decreased showing room temperature values of 0.038 T and 7.49 mT, for coercivity and remanence, respectively. At temperatures below 200 K the hysteresis loops were asymmetrical, opened and shifted towards negative field values