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1.
Measurements of magnetization, electrical resistivity, thermal expansion and differential thermal change were made on amorphous Fe100-xBx (9 ≦ X ≦ 21) alloys prepared by rapid quenching from the liquid state.With decreasing boron content in the alloys, the Curie temperature falls remarkably, while the magnetic moment increases sluggishly. The thermal expansion curves exhibit the invar characteristics below the Curie temperature due to a large positive spontaneous volume magnetostriction, and the reduced magnetization curves decrease much more rapidly with increasing temperature than those of other ferromagnetic amorphous alloys. 相似文献
2.
The magnetic properties of existing amorphous iron based materials, i.e., Fe--metalloid, Fe--early transition metals and Fe--rare
earth alloys, are briefly discussed for some representative alloys. The spin orientation of amorphous Fe--metalloid alloys
has been determined by the angular dependence of hyperfine interactions. It is shown that in iron--early transition metals
ferromagnetic order is not long-ranged, but determined by magnetic clusters. The magnetic hyperfine field distributions of
Fe-rich iron--early transition metals consist of a high and a low field tail. The magnetic structure has been investigated
for two representative Fe--RE (RE = Er, Ce) amorphous alloys. For the first time, the magnetic coupling phenomenon in amorphous/crystalline
multilayers has been discussed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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A. Berrada F. Gautier M.F. Lapierre B. Loegel P. Panissod C. Robert J. Beille 《Solid State Communications》1977,21(7):671-674
Magnetization, NMR and coercive force measurements were performed on amorphous Ni1?cPc alloys for concentration ranging between 0.15 and 0.25. The experimental results show that the magnetism is not of the same nature below and above some critical concentration c0 which determines the concentration ranges: the first one (0.15 < c < 0.18) presents the characters of a weak homogeneous ferromagnetism, while inhomogeneities dominate the magnetic properties of the second one (0.18 < c < 0.25). 相似文献
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B. A. Kornienkov M. A. Libman B. V. Molotilov 《Bulletin of the Russian Academy of Sciences: Physics》2012,76(1):51-53
The effect of thermal treatment in combination with an external magnetic field and/or elastic stress on the magnetic characteristics
of amorphous metal alloys of the 2NSR type is studied. The complex behavior of the magnetization and coercivity values in
dependence on the length of annealing at temperatures below crystallization is described. It is assumed that the observed
changes in the macroscopic magnetic characteristics are associated with the formation of clusters with different degrees of
exchange interaction. 相似文献
6.
NANOPERM-type FeMoCuB alloys are studied using magnetic and Mössbauer measurements in the as-prepared amorphous state. It is shown that the Fe76Mo8Cu1B15 (A) and Fe74Mo8Cu1B17 (B) alloys exhibit the magnetic dipole and electrical quadrupole interactions well detected in the room-temperature Mössbauer spectra. The thermomagnetic measurements above the room temperature indicate a vanishing of the magnetic interactions at approximately 310 K (A) and at 340 K (B), respectively. The low-temperature DC magnetic measurements show an anomaly around 200 K which is also a boundary at which zero-field Mössbauer measurements of both samples reflect the gradual “vanishing” of the electrical quadrupole interactions and appearance of another magnetically ordered component. The Mössbauer measurements in the field of 4 MA/m yield a survival of quadrupole and an enhancement of magnetic dipole interactions. 相似文献
7.
S. Ishio M. Fujikura T. Ishii M. Takahashi 《Journal of magnetism and magnetic materials》1986,60(2-3):236-242
The magnetic and mechanical properties of amorphous Fe100−xYx alloys (20 ≤ x ≤ 60) fabricated by rapid quenching have been measured. The dependence of the density, Young's modulus and magnetic moment per Fe atom on x shows a break point between x = 30 and 40, accompanied by a drastic change in the X-ray diffraction pattern. The spontaneous volume magnetostriction as well as the forced volume magnetostriction are a maximum at x = 20 and decrease rapidly with increasing x. The variation of the magnetic and mechanical properties with x is explained by a change of the local atomic arrangement in the amorphous state, reflecting the structure of corresponding crystalline compounds. 相似文献
8.
Hysteresis loop and ac susceptibility measurements were performed on three series of amorphous alloys: (AwB1-w)75P16B6Al3, where (A, B) are (Fe, Ni), (Co, Ni) and (Fe, Mn). Upon cooling, low w alloys undergo paramagne t to spin glass transitions. Alloys with higher w first experience a Curie transition to a ferromagnetic state, and then a spin freezing transition to a spin glass state. the T dependence of the width of the ac hysteresis loop is used to determine the spin freezing transition temperature. A magnetic phase diagram is presented for each alloy series and the value of w required for ferromagnetism, wC, is determined. When measured in the presence of small constant fields, the ac susceptibility of alloys with w just above wC has maxima near both transition temperatures. The field and temperature dependences of the peaks are explained by scaling arguments, used to determine the critical exponent δ for the Curie transition, and suggest that a similar scaling law holds for the ferromagnet to spin glass transition. 相似文献
9.
Dr. Johannes Zittartz 《Zeitschrift für Physik A Hadrons and Nuclei》1968,217(2):155-169
The magnetic susceptibility of dilute magnetic alloys is calculated using the Nagoaka approximation to the Kondo problem. We use the exact solutions of the Nagaoka equations, or equivalently Suhl's dispersion relations, as obtained recently. Our result is represented by a universal function of a certain temperature parameter. In the case of ferromagnetic coupling no appreciable change of the free spin susceptibility is found over the whole temperature range. In the case of antiferromagnetic coupling we find that the free spin susceptibility is greatly reduced. In fact, for spin 1/2, the result indicates the breakdown of the expansion in terms of the impurity concentration and suggests the onset of impurity ferromagnetism. 相似文献
10.
F. Fernandéz Barquín J. C. Gómez Sal P. Gorria J. S. Garitaonandia J. M. Barandiarán 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,35(1):3-12
Melt-spun amorphous alloys of Fe91Zr9, Fe91Zr7B2, Fe90Zr7B3 and Fe88Zr8B4 have been characterized by AC susceptibility at frequencies between 30 Hz and 10 KHz. The measurements reflect the existence of reentrant spin glass transitions below 40 K for all cases. The transition shift per frequency decade is large compared to the observed in conventional spin-glass alloys. The shift value increases with the boron content and becomes closer to values in fine-particle systems. We find that the relaxation in Fe91Zr9 follows a critical slowing down at the reentrant transition, with exponents
and
. The non-linear susceptibility displays a peak at the transition in this alloy, but wider than in canonical spin glasses. A Vogel-Fulcher (VF) activation process can explain the frequency variation in all the Fe-Zr-B alloys. The reduction of the ideal glass temperature in the VF approach, found in the higher Boron content alloys, is an indication of a superparamagnetic-like behavior. The behavior shown by these alloys is intermediate between a collective freezing and superparamagnetic-like relaxation. We propose that this is arising due to a heterogeneous spin structure. The inclusion of a reduced amount of B, affects the magnetic spin structure.Received: 13 May 2003, Published online: 22 September 2003PACS:
75.50.Lk Spin glasses and other random magnets - 75.50.Kj Amorphous and quasicrystalline magnetic materials - 75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)J.S. Garitaonandia: Present address: Dept. Física Aplicada, F. Ciencias, Universidad del País Vasco, Bilbao 48080, Spain 相似文献
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The paper reviews selected results of the extended experimental investigations of magnetic properties, time–temperature stability and workability of the soft magnetic amorphous alloys controlled by structural magnetic relaxation. Complex approach to the magnetic relaxations in multicomponent amorphous alloys is presented. The transition from magnetic after-effect to a new MAE spectrometry is illustrated on ternary amorphous CoSiB alloy. 相似文献
13.
The different diffusion processes that occur in electrodeposited Co-P amorphous alloys when they are subjected to magnetic annealing at different temperatures are studied by Coercive field measurements. Different processes are identified with different activation energies: 0.19 eV (stress relaxation): 0.75 eV (directional order); 2.9 eV (crystallization process). The low value of the activation energy for the first mechanism is identified with the diffusion of H, and that of the second with the diffusion of P. 相似文献
14.
Magnetic and electrical properties of amorphous Mn-Y, Mn-Zr, and Mn-Nb alloys have been investigated. All these alloys have a temperature-dependent susceptibility which is well fitted by a Curie-Weiss law. This implies the existence of localized magnetic moments associated with the Mn atoms. In addition, amorphous Mn-Y alloys exhibit spin-glass characteristics at low temperature. The experimental results of the electrical resistivity show that the temperature coefficient of resistivity (TCR) of both Mn-Y and Mn-Zr are negative, while Mn-Nb has a positive TCR. On the other hand, the resistivity-temperature curves of Mn-Zr and Mn-Nb have nearly the same tendency but are different from that of Mn-Y. 相似文献
15.
Amorphous Zr1?xFex samples were prepared in the composition range 0.2 ? x ? 0.9 either by means of vapour deposition or melt spinning. The electrical resistivity was determined in the range 4.2–300 K. Negative temperature coefficients were observed in the whole concentration range. The extended Ziman theory (diffraction model) was found to be able to explain these results only if the effective valence of the Fe atoms involves not only s electrons but also d electrons. The magnetic properties and the 57Fe Mössbauer effect of the Zr1?xFex alloys were studied in the range 4.2–300 K. The Fe-rich alloys are ferromagnetic. The Fe moment vanishes in alloys of an Fe concentration lower than about 50 at%. In most alloys (x ? 0.8) the Curie temperature is below room temperature and continuously decreases with Zr concentration. By means of Mössbauer spectroscopy and magnetic measurements it is shown that compositional short-range order (CSRO) is present to a higher degree in melt-spun alloys than in vapour-deposited alloys. The effect of sign and magnitude of the heat of solution on CSRO and the magnetic properties is discussed. 相似文献
16.
T. Miyazaki Yang Xingbo K. Takakura M. Takahashi 《Journal of magnetism and magnetic materials》1986,60(2-3):211-218
The structural analysis and investigation of magnetic properties were carried out on rapidly quenched Fe100−xSmx (10.5 x 80) alloys. Amorphous alloys are fabricated in a wide composition range from x = 17 to 72.5. After heating the amorphous alloys up to 900 K, they transform into metastable phase I (Tc = 465 K)+ -Fe (x < 20), metastable phase II (Tc = 555 K)+-Fe (20 x 33.3) and Fe2Sm+Sm (x40). The composition dependence of Curie temperature and magnetization is found to be similar to that of amorphous Fe-(Nd, Pr) alloys. A maximum coercive force of about 1.1 kOe at 300 K and 12 kOe at 77 K is obtained in the x = 40 alloy. The rapid decrease in coercive force with raising temperature can be explained by the wall pinning model proposed by Gaunt. The pronounced composition dependence of these magnetic properties for the amorphous Fe-Sm alloys can be considered to be caused by the change in the short-range atomic order with Sm concentration on the basis of the results of X-ray structural analysis. 相似文献
17.
The magnetic properties of various amorphous alloys of the type R1-xFex (R = Sm, Gd, Tb, Dy, Ho, Er, Tm, Lu) have been determined in the concentration range 0.3 ? x ? 0.5. With the exception of the Gd and Lu alloys pronounced thermomagnetic history effects were observed in the temperature dependence of the magnetization. These effects are due to a strong temperature dependence of the coercive force (Hc) which is found to obey an exponential law of the form Hc ∞ exp(-αT). 57Fe Mössbauer spectra were obtained on the alloys of a composition close to 40 at% Fe. From the combined results of the Mössbauer spectroscopy and magnetic measurements it is derived that the Fe moment decreases if one passes through the rare-earth series. It is postulated that this decrease is due to small differences in the compositional short-range order in the amorphous alloys caused by the heat of mixing becoming more negative in the same sense. 相似文献
18.
Magnetic susceptibility measurements of strain-free dilute alloys of Eu in Mg indicate that the Eu is predominantly divalent with ground state. The analysis indicates no solid solubility of Eu in Mg. 相似文献
19.
Z. G. Huang 《Hyperfine Interactions》1992,69(1-4):553-556
A spin spatial distribution in terms of an expansion in spherical harmonics containing deviation parameters from the symmetry axis P (0, ?) is used to describe the moment distribution of amorphous ribbon alloys. According to the theoretical analysis and Mössbauer measurement, P (0, ?) values and squareness Sxy (0, ?) and Sz can be obtained. The P (0, ?) distribution of FeNiSiBC and hydrided FeCrSiB amorphous alloys are studied. 相似文献
20.
Using polarised neutrons, the full three-dimensional magnetic structure amplitudes in the Ni1?c Ru c single crystals forc = 0·027, 0·033 and 0·046 were measured. Moment density maps in various portions of the Wigner-Seitz cell were obtained. It is seen from these maps that unlike Ni-based alloys with 3d impurities, the introduction of Ru to the Ni matrix produces extensive perturbations in the diffuse moment density, giving rise to a netpositive diffuse moment which tends to increase with Ru concentration. The asphericity of the host moment at first increases and then decreases with increasing Ru content. Another significant outcome of the present study is the evidence for the reversal of the sign of the Ru moment, from negative to positive, obtained by comparing the shape of the spherical site form factors of the three-alloy concentrations with the Ni spherical form factor itself. The sign reversal of the impurity moment is confirmed by the form factor analyses. Strong local environmental effects seem to play a major role in this alloy system. 相似文献