Amorphous Transition Metal-metalloid Alloys Research Articles

Amorphization in iron nitride thin films prepared by reactive ion-beam sputtering

Reactive ion-beam sputtering has been used to prepare iron nitride over a wide composition range. It is found that the samples deposited at room temperature exhibit amorphous phase in the composition range from $12\phantom{\rule{0.3em}{0ex}}\mathrm{at}.\phantom{\rule{0.2em}{0ex}}%$ nitrogen to $23\phantom{\rule{0.3em}{0ex}}\mathrm{at}.\phantom{\rule{0.2em}{0ex}}%$ nitrogen. For samples deposited at liquid nitrogen temperature the system is amorphous up to $35\phantom{\rule{0.3em}{0ex}}\mathrm{at}.\phantom{\rule{0.2em}{0ex}}%$ nitrogen. Amorphization can be understood in terms of a frustration in the system due to a competition between $\ensuremath{\alpha}$ and $\ensuremath{\epsilon}$ phases. Kinetic constraints are also found to play a role in the amorphization process. M\"ossbauer measurements suggest that the local order in the amorphous phase consists of a mixture of $\ensuremath{\alpha}\text{\ensuremath{-}}\mathrm{Fe}$--like and $\ensuremath{\epsilon}\text{\ensuremath{-}}{\mathrm{Fe}}_{3}\mathrm{N}$--like short-range orders. On the iron rich side the amorphous phase exhibits two-step crystallization, with a primary $\ensuremath{\alpha}\text{\ensuremath{-}}\mathrm{Fe}$ phase precipitating out in the first step. Around $22\phantom{\rule{0.3em}{0ex}}\mathrm{at}.\phantom{\rule{0.2em}{0ex}}%$ nitrogen the system exhibits a single step isomorphous transformation to $\ensuremath{\epsilon}$ phase. Thus, amorphous iron nitride phases exhibit behavior very similar to the conventional transition metal-metalloid amorphous alloys. In the remaining composition range nanocrystalline phases are formed. The amorphous magnetic iron nitride phases are expected to have distinct advantages over their crystalline counterparts in terms of soft magnetic applications.

Structure and density of transition metal-metalloid amorphous alloys

By careful study of the Rhomb Unit Structural Model (RUSM), mathematical expressions for the peak positions r n in the G(r) curve, the size of the short-range order r s, η (packing density) and density ϱ of transition metal-metalloid (TM-M) amorphous alloys are given. With these expressions, γ n , γ s , η, ϱ of palladium-, nickel-, cobalt- and iron-based TM-M amorphous alloys are calculated. The results calculated from RUSM have been shown to agree reasonably well with those from experiments on real amorphous alloys. Furthermore, the successive characteristics of the arrangements of these molecular units which constitute the overall structure of the metal glass is discussed, which indicates that there is no possibility for the existence of the so-called low-density crystal boundary in amorphous alloys.

ChemInform Abstract: On the Structural Aspects of Magnetism in Transition Metal‐Metalloid Amorphous Alloys

Abstract Transition metal-metalloid amorphous alloys generally have very soft ferromagnetic properties and low electrical conductivity compared to ferromagnetic crystalline alloys. However, the reasons for this are not well understood. The principal difference between a metallic glass and its crystalline counterpart is in the structure and this paper examines the effect of structure on solid-state magnetic interactions like spin-spin coupling, spin-orbit coupling and spin-lattice coupling via the orbital electrons. In the present study, the interaction between the intensely heterogeneous (noncentral) crystal field and the aspherical charge distribution in the paramagnetic ion is seen to introduce large magnetocrystalline anisotropy in crystalline ferromagnets. The width of the domain walls and the magnitude of the hysteresis may be understood on the basis of the magnetic anisotropies in the system and the above mentioned magnetic interactions. In a metallic glass, because of the metastable nature of the structure and the spherically symmetric distribution of material around any atom in the short-range-ordered amorphous clusters, it is argued that the crystal field would be weak, and perhaps central. This would result in an unquenched orbital magnetic moment, a weak orbit-lattice coupling and hence a weak spin-lattice coupling for the paramagnetic ion. The low hysteresis and weak magnetocrystalline anisotropy observed in metallic glasses may be explained on the basis of the above results. In this case, the spin-spin exchange interaction would dominate over the magnetocrystalline anisotropy giving rise to relatively wide and shallow domain walls.

Positron lifetime in amorphous transition metal-metalloid alloys

Positron lifetime measurements have been performed in transition metal-metalloid amorphous alloys. The increased positron lifetime observed in ternary amorphous alloys is attributed to the distortion of their local structure caused by the introduction of a second transition metal element. Chemical interaction between the constituents seems to affect the local structure more than their relative atomic size.

On the structural aspects of magnetism in transition metal-metalloid amorphous alloys

Transition metal-metalloid amorphous alloys generally have very soft ferromagnetic properties and low electrical conductivity compared to ferromagnetic crystalline alloys. However, the reasons for this are not well understood. The principal difference between a metallic glass and its crystalline counterpart is in the structure and this paper examines the effect of structure on solid-state magnetic interactions like spin-spin coupling, spin-orbit coupling and spin-lattice coupling via the orbital electrons. In the present study, the interaction between the intensely heterogeneous (noncentral) crystal field and the aspherical charge distribution in the paramagnetic ion is seen to introduce large magnetocrystalline anisotropy in crystalline ferromagnets. The width of the domain walls and the magnitude of the hysteresis may be understood on the basis of the magnetic anisotropies in the system and the above mentioned magnetic interactions. In a metallic glass, because of the metastable nature of the structure and the spherically symmetric distribution of material around any atom in the short-range-ordered amorphous clusters, it is argued that the crystal field would be weak, and perhaps central. This would result in an unquenched orbital magnetic moment, a weak orbit-lattice coupling and hence a weak spin-lattice coupling for the paramagnetic ion. The low hysteresis and weak magnetocrystalline anisotropy observed in metallic glasses may be explained on the basis of the above results. In this case, the spin-spin exchange interaction would dominate over the magnetocrystalline anisotropy giving rise to relatively wide and shallow domain walls.

Density of States in Transition Metal–Metalloid Amorphous Alloys

AbstractThe electronic density of states in transition metal–metalloid non‐crystalline alloys is calculated using the recursion method and the tight binding linear muffin tin orbital method. In the total density of states the main peak is observed near the Fermi energy. The density of states at the Fermi energy in Ni0.7B0.3(1−x)P0.3x non‐crystalline alloys decreases with increasing concentration of phosphorus.

Preparation of refractory transition metalMetalloid amorphous alloys and their thermal stability

A series of refractory transition metal (TM)-metalloid amorphous alloys, (M 1−xM′ x) 80Si 10B 10 were prepared by using a single-roller melt-spinning apparatus where M and M′ represent TMs. The crystallization temperature (T x) of these amorphous alloys increased with average outer electron concentration of TM (e/a) and became highest for the alloys with e/a between 5.6 and 5.7. It was observed that T x decreased with the period of the alloyed TM in the order of 5d TM > 4d TM > 3d TM. Hence, amorphous alloys based on tantalum and tungsten showed a very high thermal stability and (Ta 0.3W 0.7) 80Si 10B 10 alloy ( e/ a = 5.7) exhibited the highest crystallization temperature (1456K). T x to T m (melting temperature) ratios of the investigated alloys were observed to be between 0.4 and 0.52.

ChemInform Abstract: Chemical Composition and Magnetic Interactions in Amorphous Transition Metal‐Metalloid Alloys

ChemInformVolume 18, Issue 50 Reviews ChemInform Abstract: Chemical Composition and Magnetic Interactions in Amorphous Transition Metal-Metalloid Alloys R. JAGANNATHAN, R. JAGANNATHAN Edited by Rao, C. N. R. ;Indian Natl. Sci. Acad., New Delhi, IndiaSearch for more papers by this author R. JAGANNATHAN, R. JAGANNATHAN Edited by Rao, C. N. R. ;Indian Natl. Sci. Acad., New Delhi, IndiaSearch for more papers by this author First published: December 15, 1987 https://doi.org/10.1002/chin.198750372Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume18, Issue50December 15, 1987 RelatedInformation

The structure of dense-packed metallic and oxide glasses

Despite obvious differences, the structures of silicate glasses and amorphous binary alloys display some remarkable similarities. In particular, it can be argued by analogy with the amorphous transition metal-metalloid alloys, that the structure in the dense-packed regions of alkali and alkaline earth silicates exerts a significant influence on the overall structure of the glass. Preliminary results are presented of an investigation of the environment of typical ‘network-modifying’ cations in silicate glasses by neutron scattering with isotopic substitution of Ca and Li. The immediate neighbourhood of each cation appears to be ordered with a suggestion that organisation extends to second-neighbours, at least.

Preparation and crystallization of chromium-based amorphous alloys

The glass formability of the Cr72 (B, Si, C)25Al3 system has been investigated. Samples were prepared by rapid quenching from the melt by the melt spinning technique. Of the compositions investigated, only Cr72B10C10Si5Al3 and Cr71 C17Si8Al3 formed fully amorphous alloys. These showed crystallization temperatures of 997 and 990 K, respectively, among the highest reported for transition metal-metalloid amorphous alloys. The crystallization products have been found to be Cr7C3 and Cr3(Si, B) for Cr72B10C10Si5Al3 and Cr7C3 and Cr3Si for Cr72C17Si8Al3. The effects of substituting iron in place of chromium in Cr72C17Si8AI3 have been investigated. For up to 20 at% Fe the crystallization products are (Cr, Fe)7C3 and Cr3Si. An alloy with 30 at% Fe crystallizes into (Cr, Fe)7C3 and hexagonal Cr-Si-C.

Magnetovolume effect in transition metal-metalloid amorphous alloys

The thermal expansion, spontaneous volume magnetostriction ω s, forced volume magnetostriction ( ∂ω ∂H ) and Young's modulus of amorphous Fe-B, Fe-P, Co-B and (Fe-M) 77Si 10B 13 ( M = Cr, Mn, Co, Ni) alloys have been measured to make clear the magnetovolume effect in transition metal-metalloid amorphous alloys. The thermal expansion coefficient α, ω s and ( ∂ω ∂H ) are dependent on the number of d-electrons per transition metal atom n eff calculated based on the charge transfer model. The n eff vs. α, ω s and ( ∂ω ∂H ) curves are quite similar to the corresponding curves in fcc alloys. The maxima in those curves are, however, found at n eff ≈ 8.2 for the amorphous alloys in contrast with n eff ≈ 8.7 for the fcc Fe-Ni alloys. On the other hand, Young's modulus measured under the saturation of magnetization is governed by the molar volume, irrespective of n eff. The magnetovolume effect in transition metal-metalloid amorphous alloys is discussed in connection with the instability of ferromagnetism of amorphous Fe.

遷移金属‐半金属非晶質合金のＹｏｕｎｇ率への磁気体積効果の寄与

The temperature dependence of Young's modulus of transition metal-metalloid amorphous alloys, (Fe1-xM)85B15 (M: Cr, Mn, Co, Ni), (Fe1-xMx)77Si10B13 (M: Co, Ni), Fe-B, Fe-P, Co-B, has been measured by a pulse echo delay-line technique in the temperature range from R.T. to 600°C. Young's modulus Es measured under the saturation of magnetization for Mn and Cr containing alloys shows softening below Tc because of the magnetovolume effect. The contribution of the magnetovolume effect to Young's modulus is quantitatively analysed and its dependence on the electron number per transition metal atoms neff is presented. The magnetovolume contribution to Young's modulus passes through a maximum at neff∼8.0 and smears above neff∼8.3. These results are discussed in connection with the anomalous stress dependence of the magnetovolume coupling constant in the transition metal-metalloid amorphous alloys.

Correlation between the residual resistivity and the temperature resistance minimum in amorphous alloys

A simple formula for the correlation between the residual resistivity and the temperature resistivity minimum in amorphous transition metal-metalloid alloys is derived by means of the Ziman potential scattering theory and the Kondo spin-flip scattering theory.

Critical behavior of amorphous ferromagnetic alloys

The results of our systematic magnetization and electrical resistivity measurements on amorphous transition metal-metalloid alloys are reviewed. In the real critical region, the amorphous ferromagnetic alloys (with composition well above the percolation threshold) and crystalline ferromagnets are found to behave alike but outside this temperature region, they exhibit a completely different behavior. These observations are discussed in the light of existing theories and shown to provide a straightforward explanation for a large scatter in the exponent values of glassy ferromagnets found in the literature. For Ni-rich Fe-Ni based glasses, only a small fraction of spins participates in the order-disorder transition. This finding is shown to have an important bearing on the nature of phase transitions in the spin systems with quenched disorder. We present a simple model for the peculiarities observed in the critical behavior of amorphous ferromagnets.

On the validity of 57Fe hyperfine field distribution calculations from Mössbauer spectra of magnetic amorphous alloys

The approximations which are made in 57Fe hyperfine field distribution calculations from magnetic amorphous alloys are discussed. A diagram which gives an immediate indication of the validity of a given hyperfine field distribution obtained using first order perturbation theory is proposed. The assumption about the distribution of the polar angles of the hyperfine field direction with respect to the EFG principal axes in transition metal-metalloid amorphous alloys is discussed. The asymmetries of the Mössbauer spectra of the latter alloys are also considered.

Crystallization of amorphous metal-metalloid alloys

Mössbauer spectroscopy is used to study the crystallization of amorphous transition metal-metalloid alloys. Simultaneous measurements of γ-transmission spectra and conversion electron emission spectra show that on all samples measured the crystallization starts at the ribbon surface. When the annealing is done in vacuum, the first traces of crystalline phases appear on the dull ribbon surface which had been in contact with the quenching roller. If an argon atmosphere is used during the heat treatment the onset of crystallization is first observed on the shiny ribbon surface. The crystallization temperature also depends on the atmosphere used during annealing.

Atomic structure of zero-magnetostrictive amorphous Fe 4.7Co 70.3Si 15B 10 alloy

The atomic radial distribution function (RDF) of zero-magnetostrictive Fe 4.7Co 70.3Si 15B 10 amorphous alloys was determined by the energy-dispersive X-ray diffraction technique. The nature of the atomic short-range order in the alloy was investigated by examining the structure of the crystalline compounds with similar compositions and by comparing the RDF of this alloy with those of similar amorphous alloys. It is suggested that the metalloid elements in this alloy retain a high degree of compositional short-range order, just as in many other transition metal-metalloid amorphous alloys.

EXAFS Spectroscopy with Amorphous Transition Metal-Metalloid Alloys

Abstract EXAFS measurements were performed with amorphous T80M20 (T=Fe,Co, Ni; M=B,P). For the interpretation of the EXAFS spectra it was necessary also to compare them with spectra obtained from crystalline specimes with known atomic arrangement and with similar chemical composition such as the alloys Fe2B, CO3B, Ni3B as well as Fe3P, CO3P, and Ni3P. As a radiation source the Ag-target of a rotating anode X-ray generator (6 kW) was used. The spectra were obtained using a flat LiF-(220) monochromator. The specimens were kept at 80 K and thus thermal effects could be reduced. The EXAFS spectra of the amorphous alloys and those of the corresponding crystalline compounds of the type T3M show among each other a relatively great similarity. The greatest similarity exists in the case of the Ni-and Co-alloys. The amorphous alloys based on iron however show larger discrepancies with respect to the corresponding crystalline ones, where the greatest deviation occurs with the compound Fe2B. The Fourier transforms show such similarities too. The EXAFS spectra of the crystalline elements Fe. Co, and Ni as well as their Fourier transforms evidently show differences compared to the amorphous specimens and to the T3M compounds. The similarities observed between the amorphous alloys and the corresponding crystalline specimens of the T3M-type together with their large discrepancies with respect to the pure metals led to the conclusion that the local structure in the amorphous alloys is in considerable accordance with that of the corresponding T3M-compound.

Magnetostriction and magnetoelastic effects in certain amorphous alloys

Magnetoelastic phenomena in amorphous transition metal-metalloid alloys have been studied. It was found that the magnetoelastic coupling coeficient B(0) of amorphous FeSiB alloys depends mostly on the Fe content, and does not depend significantly on the B/Si ratio. The value of B(0) exhibits a maximum at about 80 at% Fe. The forced volume magnetostriction is a strongly increasing function of iron concentration above 75 at% Fe. The ΔE effect of as-quenched amorphous alloys is not a simple function of saturation magnetostriction λ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</inf> . The ΔE effect is proportional to the magnetomechanical coupling coefficient. The observed magnetoelastic effects may be related to the appearance of weak ferromagnetism in Fe-base amorphous alloys.

Ferromagnetic resonance in amorphous alloys

The frequency and temperature dependences of the magnetic properties of amorphous transition metal-metalloid alloys are studied by means of ferromagnetic resonance (FMR). In the series (TM x Ni 1− x ) 75P 16B 6Al 3, TM = {Fe, Co}, it is found that, while the frequency dependence of the FMR linewidth, Γ, in all these materials is well characterized by the usual Landau-Lifshitz-Gilbert relaxation parameter, there is also a frequency independent contribution to Γ. This is attributed to a static magnetic non-uniformity. In addition, the FMR linewidths increase at low T (with decreasing T) in the alloys with a low spin concentration, x. This effect is linked to the development of a dynamic magnetic inhomogeneity in these alloys at low T and is thought to be related to the onset of a spin glass state (in zero field) at low temperatures. Finally, the T dependence of the magnetization shows that the magnetic excitations in the high x alloys are spin waves. However, in the more dilute alloys the spin wave description is no longer valid. A simple model of clusters of strongly coupled spins (“buoys”) embedded in a “sea” of weakly coupled spins is suggested to qualitatively account for all of the data.