共查询到20条相似文献,搜索用时 15 毫秒
1.
J. E. Frackowiak 《Hyperfine Interactions》1990,54(1-4):793-797
The Mössbauer technique was used to measure the hyperfine magnetic field and isomer shift of57Fe nucleus in the ordered and disordered Fe3Al alloys. The Mössbauer spectra were analyzed to yeld the hyperfine magnetic field distribution curves. A linear correlation has been revealed between the average hyperfine field and the average number of Al atoms in the first two nearest neighbour shells of57Fe nucleus,N Al, for both ordered and disordered alloys. The measured values of the mean isomer shift agree very well with the values expected from the Miedema-Van der Woude model. 相似文献
2.
57Fe Mössbauer study of amorphous and nanocrystalline Fe73.5Nb3Cu1Si13.5B9 after neutron irradiation
57Fe Mössbauer spectroscopy is used to study neutron irradiation induced changes in the short-range order of Fe73.5Nb3Cu1Si13.5B9 alloy. The samples are investigated in both amorphous and nanocrystalline states. Neutron irradiation leads to an increase of the standard deviation of a hyperfine field distribution (HFD), implying rearrangement of the atoms towards disordering. Simultaneously, changes in the average value of the hyperfine field and a net magnetic moment position occur as a consequence of a spin reorientation, atom mixing and microscopic stress centres which are introduced by neutron irradiation. 相似文献
3.
We obtained57Fe hyperfine field parameters from Fe1−x-Co
x
alloys (0≤x≤0.6) from 77 K to 900 K. We first discuss the origin of the low temperature hyperfine fields in terms of the 3d and 4s electrons
at57Fe atoms. The57Fe hyperfine magnetic field (hmf) of Fe-Co alloys depends more weakly on temperature than the hmf of pure Fe. This temperature
dependence occurs because the alignment of the magnetic moments at both the Fe atoms and at the Co atoms depend on temperature
in the same way as the bulk magnetization of Fe-Co alloys. 相似文献
4.
The short-range order around boron, aluminum, and iron atoms in Fe75B25 and Fe70Al5B25 amorphous alloys has been studied by 11B and 27Al nuclear magnetic resonance at 4.2 K and 57Fe Mössbauer spectroscopy at 87 and 295 K. The average magnetic moment of iron atoms μ(Fe) in these alloys has been measured by a vibrating sample magnetometer. It has been revealed that the substitution of aluminum atoms for iron atoms does not disturb μ(Fe) in the Fe70Al5B25 alloy, gives rise to an additional contribution to the 11B NMR spectrum in the low-frequency range, and shifts maxima of the distribution of hyperfine fields at the 57Fe nuclei. In the Fe70Al5B25 amorphous alloy, the aluminum atoms substitute for iron atoms in the nearest coordination shells of boron and iron atoms. This alloy consists of nanoclusters in which boron and iron atoms have a short-range order of the tetragonal Fe3B phase type. 相似文献
5.
V. Rusakov S. Yaroslavtsev M. Matsnev T. Kulova A. Skundin S. Novikova A. Yaroslavtsev 《Hyperfine Interactions》2014,226(1-3):791-796
Lithium iron phosphates LiFe1-y Co y PO4 (y = 0, 0.1, 0.2) exposed to a charging process were studied by 57Fe Mössbauer spectroscopy taking into account XRD and SEM data. Hyperfine parameters of the spectra were determined above and below the magnetic ordering temperature for all the samples. It was shown that the presence of Co impurity atoms in lithium phosphates gives no effect on the hyperfine interaction of 57Fe2+ cations. However, Co atoms in the nearest cation environment of Fe atoms lead to a significant change of the hyperfine interactions of 57Fe3+ cations. The Co impurity atoms distribution over the positions of the iron atoms in the structure is found not to be statistical,but correlated. 相似文献
6.
《Journal of magnetism and magnetic materials》2002,248(2):341-347
The crystallographic structures, magnetic properties and hyperfine interactions of NdFe9.25Si1.75Cx have been studied using neutron diffraction, magnetic and 57Fe Mössbauer spectra measurements. The refinement of the powder neutron diffraction demonstrates that NdFe9.25Si1.75C1.5 crystallizes in the BaCd11-type structure with space group I41/amd and four formula units per unit cell. Nd atoms occupy 4a sites, and Fe atoms distribute on 4b, 8d and 32i sites. Si and C atoms occupy 8d and 8c sites, respectively. The saturation magnetization, the isomer shift (IS) and the hyperfine field reach their highest values at the carbon content x=1.0. With a set of phenomenological formulas, the contribution of the magneto-volume effect and the chemical bonding effect to the hyperfine parameters are successfully separated. The pure magneto-volume effect and the pure chemical bonding effect influence the hyperfine field and the IS differently. The former one increases both of them and the latter one decreases them. This is consistent with the rather strong bond between Fe(32i) and C(8c). 相似文献
7.
J. Sarzyński M. Budzyński R. Wasiewicz H. Spustek W. Tańska-Krupa M. Subotowicz 《Hyperfine Interactions》1991,62(4):273-281
Mössbauer (57Fe) and TDPAC spectroscopy (181Hf) have been used to study quasibinary compounds Zr(Fe1?x Al x )2 forx≤0.20. It has been found that the dependence of the mean values of the hyperfine magnetic field, quadrupole splitting and isomer shift on the Al concentrationx is strong. The dependence of the hyperfine magnetic field on the number of Al atoms as nearest and next-nearest neighbours of57Fe has been established. The TDPAC results also indicate a dependence of the hyperfine field on181Ta on Al concentration. 相似文献
8.
C. Bansal H. KawanakaH. Bando A. SasaharaR. Miyamoto Y. Nishihara 《Solid State Communications》2003,128(5):197-202
57Fe Mössbauer spectroscopic studies were carried out on the single layered perovskite, LaSrFeO4, in the temperature range 15-380 K. The observed line width asymmetries in the line shapes of the spectra were understood to arise from a chemical disorder of La3+ and Sr2+ ions in the block layer of the perovskite structure. The temperature dependence of the hyperfine magnetic field, quadrupole interaction, and isomer shift observed for the system was also analyzed in terms of the local environment of Fe atoms in this structure. 相似文献
9.
The temperature dependence of the57Fe hyperfine magnetic field (hmf) in Fe-Ni is stronger than the temperature dependence of the57Fe hmf in pure Fe. By analyzing the shape of the57Fe hmf distribution, and with the help of experiments with Si in Fe-Ni, we deduce that this anomalous temperature dependence originates from a large thermal sensitivity of the magnetic moments at those Fe atoms with more Ni nearest neighbors. A strong temperature dependence of the recoilfree fraction was also observed in Fe-Ni alloys. We suggest that a large mean square thermal displacement of Fe atoms in Fe-Ni is the cause of the anomalous temperature dependence. 相似文献
10.
The 57Fe Mössbauer effect measurements were made for the L10 ordered Fe-Pt alloys with 39-62 at% Pt and the effect of local atomic environment on the hyperfine structure was investigated. Furthermore, the thermal stability of magnetic order was investigated for the alloys with high Pt concentration. From the analyses of the observed Mössbauer spectra, we found that dipole-field-like anisotropic transferred hyperfine fields are mainly responsible for the large difference in hyperfine field between Fe-site and Pt-site in the Fe-rich alloys. In the Pt-rich region far from stoichiometry, the existence of many Fe-sites occupied by excess Pt atoms causes a distribution of exchange fields. Therefore, the iron atoms in different local environments may have their several hyperfine fields with different temperature dependence. The anomalous temperature dependence of the averaged hyperfine field and line broadening observed for the 61, 62 at% Pt alloys can be understood from the co-existence of various sub-spectra with different temperature dependence. As a result, the thermal stability of magnetic order is largely reduced as the Pt concentration exceeds 60 at%. 相似文献
11.
The crystal and magnetic properties of Dy2Fe17, Dy6Fe23, DyFe3 and DyFe2 intermetallic compounds are investigated with X-ray, magnetometric, 57Fe and 161Dy Mössbauer effect methods. The X-ray analysis shows that investigated compounds are single phases with Th2Ni17, Th6Mn23, PuNi3 and NgCu2 type crystal structures, respectively. The magnetometric measurements prove their ferrimagnetic behaviour, localization of Fe magnetic moments and long range Fe-Fe exchange magnetic interactions. The crystal field effects induce magnetic anisotropy which results in local magnetic symmetry or iron atoms lower than the crystal one. This is observed by the Mössbauer effect method. The values of 161Dy hyperfine magnetic fields measured for investigated compounds exceed that found in metallic dysprosium due to polarization of conduction electrons by 3d-electrons of iron atoms. The weighted average value of 57Fe hyperfine magnetic field decreases with the increase of Dy content in the compounds. 相似文献
12.
The magnetic hyperfine fieldsB
hf near the interface in epitaxial Fe(100)/Pd thin film structures were analyzed using in-situ57Fe conversion electron Mössbauer spectroscopy.B
hf is enhanced by about 12% in the 2nd Fe monolayer and approaches the Fe bulk value after a few oscillations within 8–10 Fe monolayers. This oscillating behavior can be described by a superposition of an exponential short-range and an RKKY-like long-range exchange interaction. 相似文献
13.
The temperature dependence of the hyperfine parameters of thulium iron garnet (Tm3Fe5O12) powder was studied from 90 to 550 K using169Tm and57Fe Mössbauer spectroscopy (MB). The spectra were analyzed by least mean square fits to the transmission function. The temperature dependence of the magnetic fields of the thulium nuclei is well described by the mean field model. The coupling constants between the magnetic lattice occupied by the thulium atoms and the magnetic lattices occupied by the iron atoms were derived. 相似文献
14.
W.?Bodnar M.?Szklarska-?ukasik P.?Stoch P.?Zachariasz J.?Pszczo?a J.?Suwalski 《Pramana》2010,75(3):537-548
The synthesis of materials and the studies of crystal structure and 57Fe Mössbauer effect were performed for Tb0.27Dy0.73(Fe1?x Co x )2 intermetallics. Terfenol-D (Tb0.27Dy0.73Fe2) is the starting compound of this Fe/Co-substituted series. X-ray measurements showed evidence of a pure cubic Laves phase C15, MgCu2-type, and unit cell parameters were determined across the series. A Co substitution introduced local area, at sub-nanoscale, with random Fe/Co neighbourhoods of the 57Fe atoms.Mössbauer effect spectra for the Tb0.27Dy0.73(Fe1?x Co x )2 series at room temperature are composed of a number of locally originated subspectra due to the random distribution of Fe and Co atoms in the transition metal sublattice, and due to [1 1 1] an easy axis of magnetization. Isomer shift, magnetic hyperfine field and quadrupole interaction parameter were obtained from the spectra, both for the local area and for the bulk sample.As a result of Fe/Co substitution, a Slater-Pauling-type curve for the average magnetic hyperfine field vs. Co content was observed. It was found that the magnetic hyperfine fields corresponding to the local area also create a dependence of the Slater-Pauling-type vs. Co contribution in the Fe/Co neighbourhoods. 相似文献
15.
I. A. Presniakov I. V. Morozov A. V. Sobolev M. V. Roslova A. I. Boltalin O. S. Volkova A. N. Vasil’ev 《JETP Letters》2013,97(10):583-587
The results of the Mössbauer effect studies of layered NaFeAs arsenide in a wide temperature range are presented. The measurements at T > T N demonstrate that the main part (~90%) of iron atoms are in the low-spin state Fe2+. The other atoms can be attributed to the impurity NaFe2As2 phase or to the extended defects in NaFeAs. The structural phase transition (at T S ≈ 55 K) does not produce any effect on hyperfine parameters (δ, Δ) of iron atoms. At T < T N, the spectra exhibit the existence of a certain distribution of the hyperfine magnetic field (H Fe) at 57Fe nuclei, indicating the inhomogeneity of the magnetic environment around iron cations. The analysis of the temperature behavior of the distribution function p(H Fe) allows us to determine the temperature of the magnetic phase transition (T N = 46 ± 2 K). It has been found that the magnetic ordering in the iron sublattice has a two-dimensional type. The analysis of the H Fe(T) dependence in the framework of the Bean-Rodbell model reveals a first-order magnetic phase transition accompanied by a drastic change in the electron contributions to the main component (V ZZ ) and the asymmetry parameter (η) of the tensor describing the electric field gradient at 57Fe nuclei. 相似文献
16.
In the present paper, we discuss the local atomic environment of Fe atoms in the mechanically alloyed Fe50Al40Ni10 powders on the basis of hyperfine data estimated from 57Fe Mössbauer spectra. Bhf decreases with increasing milling time due to the diffusion of Al and/or Ni into Fe grains. Nickel atoms did not diffuse inside the first coordination sphere of Fe and if the diffusion takes place the number is not more than one atom. Analyses of P(Bhf), indicate that the high hyperfine field values ranging from 30 to 33 T have to be partially attributed to Fe crystalline nanograins and the presence of the defects in them, the hyperfine field values ranging from 15 to 30 T can be associated to the nanocrystalline bcc Fe(Al, Ni) solid solution while the low hyperfine field values (<15 T) result from Fe atoms located in the disordered grain boundaries. 相似文献
17.
Magnetization and57Fe Mössbauer measurements were carried out on RFe12–x
V
x
N
y
compounds (R=Y and Nd,x=1.7 and 2.2) and the effects of nitrogen and vanadium atoms on the57Fe hyperfine fields at the different iron crystallographic sites were investigated. The hyperfine field decreases with increasing number of vanadium neighbour atoms at all the iron sites. The hyperfine field is strongly enhanced in the nitrogen composition withy>1 where the compound tends to transform into an amorphous-like solid. The iron moment deduced from the hyperfine field increases more upon nitrogenation for the 8i-site than for the other sites, and exceeds the moment of bcc iron. 相似文献
18.
The Mössbauer effect has been used to measure the magnetic hyperfine interaction of isolated 57Fe atoms in solid xenon with an applied external magnetic field. A field dependent Mössbauer absorption spectrum is observed. The ground state of these iron atoms is a triplet, which is split in the external field. The Mössbauer spectrum was analyzed taking into consideration relaxation effects. For an applied external field of 28 kOe an internal magnetic field at the 57Fe nucleus of 700± 15 kOe was observed (external field included). 相似文献
19.
Y. Homma M. Nakada A. Nakamura S. Nasu D. Aoki H. Sakai S. Ikeda E. Yamamoto Y. Haga Y. Ōnuki Y. Shiokawa 《Hyperfine Interactions》2006,168(1-3):1175-1179
57Fe and 237Np Mössbauer ōmeasurements have been performed for NpFeGa5, which is one of the so-called neptunium 1-1-5 compounds. The 57Fe Mössbauer spectra below T N = 118 K show the magnetically ordered state. The magnitude of the hyperfine magnetic field at the 57Fe nucleus is determined to be 1.98 ± 0.05 T at 10 K. From the 237Np Mössbauer spectrum at 10 K, the hyperfine magnetic field at the 237Np nucleus is 203 T and the hyperfine coupling constant is determined to be 237 T/μB using the Np atomic magnetic moment of 0.86 μB determined by the neutron diffraction study. 相似文献
20.
Mössbauer spectroscopy with 57Fe (119Sn) probe layers is a useful method to study the local magnetic structures at buried interfaces. However interface alloying, which always exists in the real samples, have to be taken into account for accurate interpretation of experimental data. We developed an algorithm, which describes the interface intermixing in the multilayers. Substituting deposited atoms by atoms of substrate and floating of deposited atoms in the upper layers during epitaxial growth leads to the formation of asymmetric chemical and magnetic interfaces. This asymmetry in the M1/M2 superlattices can explain the difference between magnetic responses from M1 on M2 and M2 on M1 interfaces which were observed in experiments. Applying this intermixing model to the systems with probe layers located at different distances from the interfaces gives the natural explanation of hyperfine fields distributions on probe atoms and helps us clarify some discrepancies reported in the literature. 相似文献