The critical properties of the manganese perov- skite La0.67Ba0.22Sr0.11Mn1-xFexO3 (0 B x B 0.2) ... more The critical properties of the manganese perov- skite La0.67Ba0.22Sr0.11Mn1-xFexO3 (0 B x B 0.2) around the paramagnetic (PM)-ferromagnetic (FM) phase transition were investigated using modified Arrott plots and Kouvel- Fisher method based on the data of static magnetic mea- surements recorded around the curie temperature TC. Based on the evaluated critical exponents for the compounds with different x values (0.378 B b B 0.411, 1.247 B c B 1.393, and 4.018 B d B 4.73) we concluded that the PM-FM phase transition in the compound with x = 0 belongs to the three- dimensional Heisenberg universality. However, the substi- tution of Fe 3? for Mn 3? resulted in shifting the value of c toward the 3D-Ising model value and a slight increase in b. This behavior was discussed and correlated with the random distribution of Fe 3? at the Mn 3? sites and the consequent
Abstract: The magnetic properties of the alloy system Fe 3-x Mn x Si have been studied by measuri... more Abstract: The magnetic properties of the alloy system Fe 3-x Mn x Si have been studied by measuring magnetization for samples with x = 0, 0.1, 0.25, 0.5, and by thermal scanning techniques for samples with x = 0, 0.1. The results reveal that the system is ferromagnetic in this composition range. Zero field cooling and field cooling magnetization measurements indicate a similar magnetic ordering and magnetic anisotropy in all samples. The saturation magnetization for the annealed samples was higher than that for "as prepared" samples. This is attributed to the reduction of magnetic domain boundaries rather than to improving magnetic order as a result of annealing. Further, T C values determined from thermal DSC measurements are in good agreement with previously reported results based on magnetic measurements.
X-ray diffraction results show that the alloy system FeAl1−xTix develops a doubly ordered L21 pha... more X-ray diffraction results show that the alloy system FeAl1−xTix develops a doubly ordered L21 phase in addition to the B2 phase as x increases. Mössbauer spectroscopy results confirm that this alloy system remains paramagnetic down to LN2 temperature. The hyperfine parameters of the spectra for the samples with x ≤ 0.4 indicate the coexistence of cubic B2 and L21 phases.
Al substituted barium ferrite particles BaFe12-xAlxO19 with 0 ≤ x ≤ 0.8 have been prepared by bal... more Al substituted barium ferrite particles BaFe12-xAlxO19 with 0 ≤ x ≤ 0.8 have been prepared by ball milling method. X-ray diffraction (XRD) has shown that the average crystallite size for all samples under investigation is in the range 66 – 76 nm. Scanning electron microscopy (SEM) imaging indicates that the particle size is in the range 0.2 – 1.0 μm, which demonstrates that the particles are polycrystalline. It was found that Al substitution does not significantly change the particle size of BaFe12-xAlxO19. The magnetic properties have been investigated using a vibrating sample magnetometer, and the anisotropy field is estimated. It was found that the coercivity of the samples increases from 4.2 kOe to 6.0 kOe with increasing Al concentration from x = 0.0 to 0.8 due to the increase in the anisotropy field. Interparticle interactions determined from the remnant magnetization data are found to be consistent with a reversal mechanism (demagnetizing like effect) for all samples examined.
In this work, Fe100-xNix nanoparticle systems in the invar region (x = 29, 32 and 37) were prepar... more In this work, Fe100-xNix nanoparticle systems in the invar region (x = 29, 32 and 37) were prepared by the method of chemical co-precipitation. X-Ray Diffraction (XRD) patterns confirmed the coexistence of both bcc and fcc phases for x = 29 and 32. However, only fcc phase was observed for x = 37.
Abstract The results of a Mossbauer study of the alloy system CuAl 1- x Fe x are presented. Spect... more Abstract The results of a Mossbauer study of the alloy system CuAl 1- x Fe x are presented. Spectra at room temperature, at 86 K, and in the presence of a 4 kOe external magnetic field were recorded. These spectra indicate that no long-range magnetic order exists in the alloys with x ⩽ 0.3, while for x = 0.4 magnetic order develops, and superparamagnetic behavior is exhibited. The results are used to obtain information about the local chemical environment of the Fe atoms in the magnetic clusters in the alloys.
Room temperature Mössbauer spectroscopy and X-ray diffractometry have been used to study GdFe6−xC... more Room temperature Mössbauer spectroscopy and X-ray diffractometry have been used to study GdFe6−xCoxGe6 alloys (with x=0, 1, 2 and 4) and the effect of partially substituting the cobalt for iron in the alloy. The X-ray diffraction study of the alloy indicates that its crystal structure is a single phase and does not change with this substitution, apart from a reduction in the lattice constant. The Mössbauer study shows that substituting cobalt for iron in the system significantly changes its magnetic properties. As cobalt is introduced, it occupies the iron sites randomly in accordance with the binomial distribution, leading to new magnetic components of the spectra with appreciably lower magnetic fields. The reduction in the hyperfine field with cobalt concentration is due to the fact that Co in this structural phase has zero moment. At higher cobalt concentrations the hyperfine field vanishes as the material becomes magnetically disordered at room temperature.
Abstract X-ray diffraction patterns for Fe 0.75 Ni 0.25− x Cr x show that the samples with x =0 a... more Abstract X-ray diffraction patterns for Fe 0.75 Ni 0.25− x Cr x show that the samples with x =0 and 0.25 form a single bcc-type phase with a lattice parameter of 2.870 A, while the samples with x =0.05 and 0.10 form the bcc-type phase with an additional γ-fcc phase, as a minor phase with a lattice parameter of 3.585 A. On the other hand all the Fe 0.65 Ni 0.35− x Cr x samples show a single γ-fcc phase. The lattice parameter for the Fe 0.65 Ni 0.35− x Cr x is found to increase linearly with increasing chromium concentration. Mossbauer spectra for Fe 0.75 Ni 0.25− x Cr x show that all the samples are magnetically ordered and some of them have a central paramagnetic line with a very low intensity (between 2 and 15%) for the samples with x =0, 0.05, and 0.10. However, Mossbauer spectra for Fe 0.65 Ni 0.35− x Cr x show that the sample with x =0 is magnetically ordered and the hyperfine field splitting starts to collapse at x =0.05 and disappears completely at x =0.10 and above. The average isomer shift of this system is negative and it decreases with increasing Cr concentration.
Barium hexaferrite samples BaFe12−2xTixRuxO19 were prepared by ball milling and their structural ... more Barium hexaferrite samples BaFe12−2xTixRuxO19 were prepared by ball milling and their structural and magnetic properties were investigated using X-ray diffraction, TEM, Mössbauer spectroscopy, and vibrating sample magnetometry. It was found that the particle size increases appreciably, and the crystallinity improves with Ti–Ru substitution. Mössbauer spectroscopy revealed that the substitution of Fe3+ ions occurs at the 4f2 and 4f1+2a sites for low substitution, and substitution at the 2b site occurs for x≥0.2. The saturation magnetization increases up to x=0.2, and then starts to decrease for higher x values, while the coercivity decreases monotonically, recording a reduction of 55% at x=0.4. These results were interpreted in terms of the site preferential occupation of the Ti2+ and Ru4+ ions. The thermomagnetic curves for all samples showed Hopkinson peaks indicating the presence of small superparamagnetic particles in the samples. The sample with x=0.0 was found to consist of purely superparamagnetic particles, while the substituted samples were found to contain only 22–30% of the powders’ mass as superparamagnetic particles.
... Mössbauer and structural studies of Fe 0.7−x V x Al 0.3 alloys. J. Shobaki a , b , IA Al-Omar... more ... Mössbauer and structural studies of Fe 0.7−x V x Al 0.3 alloys. J. Shobaki a , b , IA Al-Omari 1 , c , Corresponding Author Contact Information , E-mail The Corresponding Author , MK Hasan a , KA Azez a , M-Ali H. Al-Akhras a , BA Albiss a , HH Hamdeh d and SH Mahmood b. ...
The critical properties of the manganese perov- skite La0.67Ba0.22Sr0.11Mn1-xFexO3 (0 B x B 0.2) ... more The critical properties of the manganese perov- skite La0.67Ba0.22Sr0.11Mn1-xFexO3 (0 B x B 0.2) around the paramagnetic (PM)-ferromagnetic (FM) phase transition were investigated using modified Arrott plots and Kouvel- Fisher method based on the data of static magnetic mea- surements recorded around the curie temperature TC. Based on the evaluated critical exponents for the compounds with different x values (0.378 B b B 0.411, 1.247 B c B 1.393, and 4.018 B d B 4.73) we concluded that the PM-FM phase transition in the compound with x = 0 belongs to the three- dimensional Heisenberg universality. However, the substi- tution of Fe 3? for Mn 3? resulted in shifting the value of c toward the 3D-Ising model value and a slight increase in b. This behavior was discussed and correlated with the random distribution of Fe 3? at the Mn 3? sites and the consequent
Abstract: The magnetic properties of the alloy system Fe 3-x Mn x Si have been studied by measuri... more Abstract: The magnetic properties of the alloy system Fe 3-x Mn x Si have been studied by measuring magnetization for samples with x = 0, 0.1, 0.25, 0.5, and by thermal scanning techniques for samples with x = 0, 0.1. The results reveal that the system is ferromagnetic in this composition range. Zero field cooling and field cooling magnetization measurements indicate a similar magnetic ordering and magnetic anisotropy in all samples. The saturation magnetization for the annealed samples was higher than that for "as prepared" samples. This is attributed to the reduction of magnetic domain boundaries rather than to improving magnetic order as a result of annealing. Further, T C values determined from thermal DSC measurements are in good agreement with previously reported results based on magnetic measurements.
X-ray diffraction results show that the alloy system FeAl1−xTix develops a doubly ordered L21 pha... more X-ray diffraction results show that the alloy system FeAl1−xTix develops a doubly ordered L21 phase in addition to the B2 phase as x increases. Mössbauer spectroscopy results confirm that this alloy system remains paramagnetic down to LN2 temperature. The hyperfine parameters of the spectra for the samples with x ≤ 0.4 indicate the coexistence of cubic B2 and L21 phases.
Al substituted barium ferrite particles BaFe12-xAlxO19 with 0 ≤ x ≤ 0.8 have been prepared by bal... more Al substituted barium ferrite particles BaFe12-xAlxO19 with 0 ≤ x ≤ 0.8 have been prepared by ball milling method. X-ray diffraction (XRD) has shown that the average crystallite size for all samples under investigation is in the range 66 – 76 nm. Scanning electron microscopy (SEM) imaging indicates that the particle size is in the range 0.2 – 1.0 μm, which demonstrates that the particles are polycrystalline. It was found that Al substitution does not significantly change the particle size of BaFe12-xAlxO19. The magnetic properties have been investigated using a vibrating sample magnetometer, and the anisotropy field is estimated. It was found that the coercivity of the samples increases from 4.2 kOe to 6.0 kOe with increasing Al concentration from x = 0.0 to 0.8 due to the increase in the anisotropy field. Interparticle interactions determined from the remnant magnetization data are found to be consistent with a reversal mechanism (demagnetizing like effect) for all samples examined.
In this work, Fe100-xNix nanoparticle systems in the invar region (x = 29, 32 and 37) were prepar... more In this work, Fe100-xNix nanoparticle systems in the invar region (x = 29, 32 and 37) were prepared by the method of chemical co-precipitation. X-Ray Diffraction (XRD) patterns confirmed the coexistence of both bcc and fcc phases for x = 29 and 32. However, only fcc phase was observed for x = 37.
Abstract The results of a Mossbauer study of the alloy system CuAl 1- x Fe x are presented. Spect... more Abstract The results of a Mossbauer study of the alloy system CuAl 1- x Fe x are presented. Spectra at room temperature, at 86 K, and in the presence of a 4 kOe external magnetic field were recorded. These spectra indicate that no long-range magnetic order exists in the alloys with x ⩽ 0.3, while for x = 0.4 magnetic order develops, and superparamagnetic behavior is exhibited. The results are used to obtain information about the local chemical environment of the Fe atoms in the magnetic clusters in the alloys.
Room temperature Mössbauer spectroscopy and X-ray diffractometry have been used to study GdFe6−xC... more Room temperature Mössbauer spectroscopy and X-ray diffractometry have been used to study GdFe6−xCoxGe6 alloys (with x=0, 1, 2 and 4) and the effect of partially substituting the cobalt for iron in the alloy. The X-ray diffraction study of the alloy indicates that its crystal structure is a single phase and does not change with this substitution, apart from a reduction in the lattice constant. The Mössbauer study shows that substituting cobalt for iron in the system significantly changes its magnetic properties. As cobalt is introduced, it occupies the iron sites randomly in accordance with the binomial distribution, leading to new magnetic components of the spectra with appreciably lower magnetic fields. The reduction in the hyperfine field with cobalt concentration is due to the fact that Co in this structural phase has zero moment. At higher cobalt concentrations the hyperfine field vanishes as the material becomes magnetically disordered at room temperature.
Abstract X-ray diffraction patterns for Fe 0.75 Ni 0.25− x Cr x show that the samples with x =0 a... more Abstract X-ray diffraction patterns for Fe 0.75 Ni 0.25− x Cr x show that the samples with x =0 and 0.25 form a single bcc-type phase with a lattice parameter of 2.870 A, while the samples with x =0.05 and 0.10 form the bcc-type phase with an additional γ-fcc phase, as a minor phase with a lattice parameter of 3.585 A. On the other hand all the Fe 0.65 Ni 0.35− x Cr x samples show a single γ-fcc phase. The lattice parameter for the Fe 0.65 Ni 0.35− x Cr x is found to increase linearly with increasing chromium concentration. Mossbauer spectra for Fe 0.75 Ni 0.25− x Cr x show that all the samples are magnetically ordered and some of them have a central paramagnetic line with a very low intensity (between 2 and 15%) for the samples with x =0, 0.05, and 0.10. However, Mossbauer spectra for Fe 0.65 Ni 0.35− x Cr x show that the sample with x =0 is magnetically ordered and the hyperfine field splitting starts to collapse at x =0.05 and disappears completely at x =0.10 and above. The average isomer shift of this system is negative and it decreases with increasing Cr concentration.
Barium hexaferrite samples BaFe12−2xTixRuxO19 were prepared by ball milling and their structural ... more Barium hexaferrite samples BaFe12−2xTixRuxO19 were prepared by ball milling and their structural and magnetic properties were investigated using X-ray diffraction, TEM, Mössbauer spectroscopy, and vibrating sample magnetometry. It was found that the particle size increases appreciably, and the crystallinity improves with Ti–Ru substitution. Mössbauer spectroscopy revealed that the substitution of Fe3+ ions occurs at the 4f2 and 4f1+2a sites for low substitution, and substitution at the 2b site occurs for x≥0.2. The saturation magnetization increases up to x=0.2, and then starts to decrease for higher x values, while the coercivity decreases monotonically, recording a reduction of 55% at x=0.4. These results were interpreted in terms of the site preferential occupation of the Ti2+ and Ru4+ ions. The thermomagnetic curves for all samples showed Hopkinson peaks indicating the presence of small superparamagnetic particles in the samples. The sample with x=0.0 was found to consist of purely superparamagnetic particles, while the substituted samples were found to contain only 22–30% of the powders’ mass as superparamagnetic particles.
... Mössbauer and structural studies of Fe 0.7−x V x Al 0.3 alloys. J. Shobaki a , b , IA Al-Omar... more ... Mössbauer and structural studies of Fe 0.7−x V x Al 0.3 alloys. J. Shobaki a , b , IA Al-Omari 1 , c , Corresponding Author Contact Information , E-mail The Corresponding Author , MK Hasan a , KA Azez a , M-Ali H. Al-Akhras a , BA Albiss a , HH Hamdeh d and SH Mahmood b. ...
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