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1.
V. S. Pokatilov 《Physics of the Solid State》2007,49(12):2217-2222
Amorphous and microcrystalline Fe-B alloys (4–25 at % B) obtained by rapid quenching of the melt were studied using the pulsed nuclear magnetic resonance (NMR) of 11B nuclei at 4.2 K. Alloy samples were prepared from both a natural isotope mixture and a mixture of the 56Fe and 11B isotopes. The NMR spectra were measured as a function of the boron content. The maximum hyperfine fields at the 11B nuclei sites are 25–29 kOe and overlap the values of the hyperfine fields at the 11B nuclei sites in the tetragonal and orthorhombic Fe3B phases and also in the α-Fe phase containing boron as a substitutional impurity. The short-range order and local atomic structure of the amorphous Fe-B alloys were determined. The amorphous alloys are found to consist of microregions (clusters) with a short-range order similar to that in the tetragonal or orthorhombic Fe3B phase or the α-Fe phase. 相似文献
2.
The lithium ion conductivity of a wide variety of rapidly quenched glasses is studied both as a function of lithium ion content and with various additives which are likely to affect the microstructure of the glass. In each of the glass systems studied a maximum ionic conductivity of ≈10?3 (ohms cm)?1 is observed at 500 K, but this value is reached for different Li ion concentrations in different systems. Experiments with additions to the glass composition suggest that the availability of vacant interstitial sites in glasses of this type is not a limitation to fast ion conduction. 相似文献
3.
Zhao Jian-gao Shen Bao-gen Zhan Wen-shan Chen Jin-chang 《Journal of magnetism and magnetic materials》1985,50(1):119-121
11B NMR study in glassy Fe100?xBx (12 ? x ? 24) suggests that B atoms will be fitted into some larger holes of Bernal polyhedrals only for x < 18, as the Polk model described. But for x ? 18, B atoms will occupy some positions of vertex sites of some polyhedras besides filling more larger holes until all of the larger holes are filled, like the Gaskell model pointed. Using this pattern, the big changes of the concentration dependence of some properties such as magnetic moments and Curie temperature at x = 18 can be interpreted. 相似文献
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Rapidly quenched lithium tungstate and molybdate glasses containing up to 20 mole% lithium chloride and bromide additives have been prepared. The additives are found to give a small increase (up to a factor of two at room temperature) in the lithium ion conductivity of the glass which can be understood in terms of models developed for network forming glasses. 相似文献
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9.
Aditya M. Vora 《Frontiers of Physics in China》2007,2(4):430-435
The theoretical investigation of the superconducting state parameters (SSP) viz. electron-phonon coupling strength λ, Coulomb pseudopotential μ*, transition temperature T
c, isotope effect exponent α and effective interaction strength N
0
V of ten Cu
C
Zr100−C
metallic glasses have been reported using Ashcroft’s empty core (EMC) model potential. Three local field correction functions
proposed by Hartree (H), Taylor (T) and Ichimaru-Utsumi (IU) are used in the current investigation to study the screening
influence on the aforesaid properties. It is observed that the electron-phonon coupling strength λ and the transition temperature T
C
are quite sensitive to the selection of the local field correction functions, whereas the Coulomb pseudopotential μ*, isotope effect exponent α and effective interaction strength N
0
V show weak dependences on local field correction functions. The T
c obtained from IU-local field correction function are found an excellent agreement with available theoretical or experimental
data. Also, the present results are found in qualitative agreement with other such earlier reported data, which confirms the
superconducting phase in metallic glasses.
相似文献
10.
By means of experiments with the domain structure of amorphous ferromagnets information about local magnetic anistropies can be obtained. The magnitude of these local anisotropies is derived from the reaction of the domains to external stresses. 相似文献
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NMR and magnetic susceptibility of CeCu6 intermetallic compound were investigated. The most important contributions to the magnetic susceptibility are the Curie-Weiss term, expressing the paramagnetism of the localized f-electrons, and a temperature independent term for which all the contributions were estimated. The phenomenological exchange constantJ sf between 4f — electron spins and conduction — electron spins is derived to be ?0·012 eV. The Knight shift and Curie temperature are discussed in terms of the Ruderman-Kittel-Kasuya-Yosida theory and in the Rocher's virtual bound states model. The s — f exchange integralΓ and the Fermi wavevectork F are derived to be — 0·8 eV and 1·32 Å?1, respectively. 相似文献
13.
Structure of rapidly quenched Al-Mn 总被引:1,自引:0,他引:1
14.
The mechanical properties of monolithic metallic glasses depend on the structures at atomic or subnanometer scales, while a clear correlation between mechanical behavior and structures has not been well established in such amorphous materials. In this work, we find a clear correlation of (27)Al NMR isotropic shifts with a microalloying induced ductile-to-brittle transition at ambient temperature in bulk metallic glasses, which indicates that the (27)Al NMR isotropic shift can be regarded as a structural signature to characterize plasticity for this metallic glass system. The study provides a compelling approach for investigating and understanding the mechanical properties of metallic glasses from the point of view of electronic structure. 相似文献
15.
V. S. Pokatilov 《Physics of the Solid State》2009,51(1):143-149
Amorphous and crystalline Fe-B alloys (5–25 at % B) were studied using pulsed 57Fe nuclear magneticr esonance at 4.2 K. The alloy samples were prepared from a mixture of the 57Fe and 10B isotopes by rapid quenching from the melt. In the microcrystalline Fe-(5–12 at %) B alloys, the resonance frequencies were measured for local states of 57Fe nuclei in the tetragonal and orthorhombic Fe3B phases and also in α-Fe. The resonance frequencies characteristic of 57Fe nuclei in α-Fe crystallites with substitutional impurity boron atoms in the nearest neighborhood were also revealed. In the resonance frequency distribution P(f) in the amorphous Fe-(18–25) at % B alloys, there are frequencies corresponding to local Fe atom states with short-range order of the tetragonal and orthorhombic Fe3B phases. As the boron content decreases below 18 at %, the P(f) distributions are shifted to higher frequencies corresponding to 57Fe NMR for atoms exhibiting a short-range order of the α-Fe type. The local magnetic structure of the amorphous Fe-B alloys is also considered. 相似文献
16.
The influence of low-temperature annealing on the magnetic hysteresis loop parameters of magnetostrictive Co-Si-B and nonmagnetostrictive Co-Fe-Si-B glasses was studied. The dependence of Curie temperature (TC), crystallization temperature (Tx), full-stress-relaxation temperature, saturation magnetostriction constant, saturation magnetization and coercive field Hc on metalloids contents for as quenched Co100-x(Si0.5B0.5)x glasses was determined.It was found that annealing enhances remanence magnetization for all investigated Co-Si-B glasses. The coercive field of these glasses is influenced by annealing owing to: stress relaxation (resulting in an Hc decrease) and domain structure stabilization (resulting in an Hc increase). Significant Hc reduction for both magnetostrictive and non-magnetostrictive glasses was observed, after annealing above TC. For glasses with TC<>Tx, it was necessary to apply an external magnetic field in ord er to decrease Hc.It was found that non-magnetostrictive metallic glasses with low Curie temperatures (TC ? 450 K) exhibit the most stable magnetic hysteresis loop parameters. 相似文献
17.
Tsay SF 《Physical review. B, Condensed matter》1993,48(9):5945-5948
18.
《Journal of Magnetic Resonance (1969)》1982,46(2):283-288
A method is presented to reduce severe magnetic susceptibility broadening of NMR spectra of powders. It involves surrounding the particles of the powder with a liquid of the same magnetic susceptibility as the powder. Results are shown for the NbHx, system. 相似文献
19.
Akihiro Makino Takeshi Kubota Chuntao Chang Masahiro Makabe Akihisa Inoue 《Journal of magnetism and magnetic materials》2008
Fe-based amorphous alloy ribbons are one of the major soft magnetic materials, because of their superior magnetic properties such as the relatively high saturation magnetization (Js) of 1.5–1.6 T and good magnetic softness. However, the preparation of the ordinary amorphous magnetic alloys requires cooling rates higher than 104 K/s due to the low glass-forming ability (GFA) and thus restricts the material outer shape. Recently, Fe-metalloid-based bulk metallic glasses (BMGs) containing glass-forming elements such as Al, Ga, Nb, Mo, Y and so forth have been developed. These alloys have high GFA, leading to the formation of BMG rod with diameters of mm-order. However, the glass-forming metal elements in BMGs result in a remarkable decrease in magnetization. Basically, Js depends on Fe content; hence, high Js requires high Fe content in the Fe-based amorphous alloys or BMGs. On the other hand, high GFA requires a large amount of glass-forming elements in the alloys, which results in lower Fe content. Therefore, in substances, the coexistence of high Js and high GFA is difficult. Since this matter should be immensely important from academia to industry in the material field, a great deal of effort has been devoted; however, it has remained unsolved for many years. In this paper, we present a novel Fe-rich FeSiBP BMG with high Js of 1.51 T comparable to the ordinary Fe–Si–B amorphous alloy now in practical use as well as with high GFA leading to a rod-shaped specimen of 2.5 mm in diameter, obtained by Cu-mold casting in air. 相似文献
20.
J. Pavlovský M. Rotter B. Sedlák Lt. Lešták M. Bartos I. Procházka M. Finger 《Hyperfine Interactions》1985,22(1-4):181-185
Hyperfine fields on Co nuclei in amorphous as-quenched and heat-treated Co75Fe5B20 samples were studied by conventional NMR and by very low temperature nuclear orientation techniques. The Co spin echo measurement at 1.4 K yielded broad spectra between 130 – 260 MHz, with narrow maxima at 145.5 MHz and 155.1 MHz for as-quenched sample and with a broad maximum at 227 MHz for heat-treated sample well below the recrystallization point. The60Co nuclear orientation measurements gave the mean value of hyperfine field Bhf15 T nearly independent of the sample heat-treatment. The spin-lattice relaxation was studied by pulse NMR and also by nuclear orientation thermal cycling technique. 相似文献