W. Ciurzyńska

Mössbauer studies and some magnetic properties of amorphous and nanocrystalline Fe87−xZr7B6Cux alloys

Abstract The structure and low-field magnetic properties (i.e. the magnetic susceptibility and its disaccommodation) for the Fe 87 Zr 7 B 6 and Fe 86 Zr 7 B 6 Cu 1 alloys in the amorphous and nanocrystalline states are investigated. It was stated that the replacement of 1 at% iron atoms by Cu atoms in Fe 87 Zr 7 B 6 leads to the decrease of the crystallization temperature. Moreover, the results obtained indicate that in the nanocrystalline alloys, besides the amorphous matrix and α-Fe grains, the interfacial zone consisting of two components may be distinguished. The volume fraction of the interfacial zone is higher for the nanocrystalline Fe 86 Zr 7 B 6 Cu 1 alloy. From studies on the magnetic susceptibility disaccommodation in investigated alloys, it is evident that the relaxation processes occurring in the amorphous phase are the main source of this phenomenon. From the analysis of the isochronal disaccommodation curves (applying a Gaussian distribution of relaxation times) the values of activation energy of the individual processes are found.

Some Magnetic Properties of Bulk Amorphous Fe–Co–Zr–Hf–Ti–W–B–(Y) Alloys

The microstructure and some magnetic properties of the bulk amorphous (Fe_0.61Co_0.10Zr_0.025Hf_0.025Ti_0.02W_0.02B_0.20)_100-xY_x (x = 0 or 2) alloys are studied. The as-quenched and annealed at 720 K for 15-min alloys, well below the crystallization temperature, as confirmed by X-ray diffraction and Mossbauer spectroscopy studies, are fully amorphous. The investigated alloys are soft magnetic ferromagnets and exhibit relatively high magnetic susceptibility at low magnetic fields. However, the alloys show broad disaccommodation spectra characteristic of amorphous materials. The intensity of disaccommodation distinctly decreases after the addition of 2 at.% of Y to the amorphous Fe ₆₁Co ₁₀Zr _2.5Hf _2.5Ti ₂W ₂B ₂₀ alloy and also after annealing at 720 K for 15 min. From the analysis of disaccommodation curves, the average activation energies of elementary processes are estimated. The obtained values of the activation energies, equal to about 1.2 eV, and preexponential factor in Arrhenius law in order of 10^- ¹⁵s indicate that observed disaccommodation phenomenon is connected with the ordering of atom pairs near free volumes. In higher magnetic fields, the magnetization fulfils <i>M</i> /<i>M</i> _s ~ 1/mu₀ <i>H</i> law, pointing out the presence of quasi-dislocation dipoles with the width lower than the exchange length. After the addition of yttrium to the amorphous Fe₆₁Co₁₀Zr_2.5Hf_2.5Ti₂W ₂B ₂₀ alloy and the annealing of the samples at 720 K for 15 min, we observe the decrease of the quasi-dislocation dipoles width.

Effect of Co addition on the microstructure and magnetic properties of FeCuNbSiB alloy

Abstract The microstructure and magnetic properties of Fe 73.5 Cu 1 Nb 3 Si 13.5 B 9 and Fe 66.5 Co 7 Cu 1 Nb 3 Si 13.5 B 9 alloys were investigated. It was found that the addition of Co atoms enhances the effective hyperfine field at 57 Fe nuclei and accelerates the crystallization process. Additionally, Fe 66.5 Co 7 Cu 1 Nb 3 Si 13.5 B 9 ribbons exhibit low disaccommodation intensity and high initial susceptibility.

Microstructure and some magnetic properties of amorphous and nanocrystalline Fe-Cu-Nb-Si-B alloys

Abstract The microstructure and magnetic properties, i.e. saturation magnetic polarization, initial magnetic susceptibility and its disaccommodation, for the amorphous and the partially crystallized Fe 73.5 Cu 1 Nb 3 Si 13.5 B 9 ribbons aged at 733 K were studied. After accumulative annealing of the samples at 733 K, the decrease of the initial susceptibility and increase of the disaccommodation intensities were observed. These are connected with the annealing out of ‘free volumes’ in the amorphous matrix, which is the main source of the magnetic after-effect in all investigated samples.

Order-disorder effect on magnetic properties of rapidly quenched Fe-6.5%Si alloy

Abstract The magnetic properties (i.e. coercivity, permeability and its disaccommodation) of Fe-6.5%Si samples in the as-quenched state and after annealing at 1370 K for 1 h, and also at 770 and 970 K for 1 h and 6 h were investigated. For these samples the ordering parameters were determined using the Mossbauer spectroscopy. The deterioration of magnetic properties of samples aged at 770 and 970 K is connected with the presence of DO3 ordering.

Microstructure and magnetic properties of Fe-Co-Nd-Y-B alloys obtained by suction casting method

The phase composition, magnetic properties i.e. coercivity and the magnetic polarization at room temperature for the bulk Fe67Co5Nd3Y6B19 and Fe64Co5Nd6Y6B19 alloys were studied. The bulk amorphous Fe67Co5Nd3Y6B19 alloy, inhomogeneous in the as-quenched state, crystallized after annealing at 948 K for 0.5 h and consisted of Nd2Fe14B-type, Fe2B and paramagnetic phases. The rapidly solidified Fe64Co5Nd6Y6B19 alloy contained the Nd2Fe14B-type and paramagnetic phases. The annealing of the bulk Fe67Co5Nd3Y6B19 alloy at 948 K for 0.5 h led to hard magnetic properties. However, the bulk Fe64Co5Nd6Y6B19 alloy exhibited good hard magnetic properties directly after preparation.

Effect of cooling rate on magnetic properties of amorphous and nanocrystalline Fe73.5Cu1Nb3Si15.5B7 alloy

Abstract The microstructure and the magnetic susceptibility with its disaccommodation and stabilization field in the Fe 73.5 Cu 1 Nb 3 Si 15.5 B 7 alloy heat treated by different cooling methods were studied. It was stated that the annealed samples cooled in air exhibit the best soft magnetic properties.

Microstructure and some magnetic properties of high-silicon FeSi sheets

Abstract The microstructure and some magnetic properties of Fe-6.42 wt% Si alloy in the as-received state and after annealing at 773 K for 1–31 h have been studied. From Mossbauer spectroscopy it was found that in all investigated samples the magnetization vector is almost randomly distributed. In the temperature range 200–400 K the intensity of the magnetic susceptibility disaccommodation is very low. Moreover, this alloy exhibits very low coercivity and high initial susceptibility.

Magnetic permeability disaccommodation in microcrystalline 6.5% Si-Fe ribbons

Abstract A magnetic disaccomodation band in microcrystalline 6.5% Si-Fe ribbons was observed at temperatures within the range 230–380 K. Activation energies of elementary processes were evaluated.

Grain orientation and low magnetic field properties of microcrystalline Fe-Si ribbons

Abstract After annealing microcrystalline Fe-6.5%Si ribbons at 1370 K for 1 h the grain surface is parallel to (100) crystal plane. Simultaneously, the coercivity (Hc) decreases while the magnetic susceptibility (χ) and the slope of virgin magnetization curve (α) increase. However, annealing at 1470 K for 20 min deteriorates the magnetic properties in comparison with previous heat treatment and makes the grain surfaces parallel to the (110) crystal plane.