J. Olszewski

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.

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.

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.

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 softening of nanocrystalline Fe74Cu1Nb3Si12B10 alloy obtained by two-step heat treatment

Abstract The magnetic properties of the nanocrystalline Fe 74 Cu 1 Nb 3 Si 12 B 10 alloy annealed at 573, 623, 673 or 700xa0K for 1xa0h and then at 823xa0K (crystallization temperature) for 0.5xa0h are investigated. It is found that the preannealing of the samples narrows grain size distribution which involves a higher initial magnetic susceptibility. However, the distribution of the grain size does not influence the magnetic susceptibility disaccommodation.

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.

The role of Nb and Cu in the creation of nanostructure in Fe-based amorphous alloys

Abstract The microstructure and coercivity of Fe 77.5− x − y Cu x Nb y Si 13.5 B 9 ( x = 0 or 1, y = 0 or 3) alloys in the as-quenched state and after accumulative annealing at different temperatures were investigated. It was found that the addition of Cu to Fe-based amorphous alloys accelerates their crystallization. Only the simultaneous addition of Cu and Nb to Fe-based amorphous alloys results in the magnetization vector becoming almost parallel to the ribbon surface and the coercivity reaching a very low value in crystalline materials.

Microstructure and temperature dependence of magnetic properties of nanocrystalline Fe42.7Co42.7Zr6.8−xNbxB6.8Cu1 (x=0,1) alloys

Abstract Heat-treated Fe 42.7 Co 42.7 Zr 6.8− x Nb x B 6.8 Cu 1 ( x =0,1) alloys were studied. During nanocrystallization of these alloys, the ordered α′-FeCo phase is formed. Moreover, the magnetic susceptibility of the nanocrystalline alloys slightly depends on temperature. Furthermore, the relaxation processes occurring in the amorphous matrix are the main source of the magnetic susceptibility disaccommodation in nanocrystalline alloys.

Magnetic behavior of amorphous and nanocrystalline Fe92−xZr7Cu1Bx (x=2 or 6) alloys

Abstract It is found that in the Fe 92− x Zr 7 Cu 1 B x ( x =2 or 6) alloys annealed at 573xa0K for 1xa0h the invar anomalies are manifested. Moreover, the nanocrystalline Fe 86 Zr 7 Cu 1 B 6 and Fe 90 Zr 7 Cu 1 B 2 alloys containing about 5% of α-Fe phase exhibit the superparamagnetic behavior (above the Curie temperature of the amorphous matrix). The appearance of the α-Fe fine grains leads to an increase of the magnetic susceptibility for the Fe 86 Zr 7 Cu 1 B 6 alloy.