Physics of Amorphous Metals

Kovalenko, N. P.; Krasny, Yu.P.; Krey, U.

doi:10.1002/3527603174

Cited by 36 publications

(34 citation statements)

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“…Skriver and coworkers have published calculations for rare earths [23] and lanthanides [24] and Sigalas and Papaconstantopoulos [36] have given a recent tabulation for d-band elements, and which are particularly valuable since usually no other estimate of λ is available. [20,21].…”

Section: Resultsmentioning

confidence: 99%

“…I It is evident from the equation (4) which was originally derived by Bogoliubov et al [36], that the Coulomb repulsion parameter µ * is essentially weakened owing to a large logarithmic term in the denominator. Here, ε (X ) is the modified Hartree dielectric function, which is written as [27] …”

Section: Theoretical Methodologymentioning

confidence: 99%

“…In the weak coupling limit of the electron-phonon interaction, the fundamental equations of the BCS theory should be derived from the Eliashberg equations. This conversion is possible upon some approximation of the phonon frequency |ω| ≥ ω D with ω D denote the Debye frequency [36]. Morel and Anderson [34] proposed the equation of the transition temperature…”

Section: Theoretical Methodologymentioning

confidence: 99%

“…Therefore, Rajput and Gupta [35] have introduced the new term 10θ D in place of the phonon frequency ω from the Butler's [32] relation for the sake of simplicity and ignoring the lattice vibrational effect, which has generated consistent results of the Coulomb pseudopotential. The parameter µ * represents the effective interelectronic Coulomb repulsion at the Fermi surface [36]. Hence, in the present case, we have adopted an equation of the Coulomb pseudopotential proposed by Rajput and Gupta [35].…”

Section: Theoretical Methodologymentioning

confidence: 99%

See 3 more Smart Citations

Study of superconducting state parameters of amorphous metals by a pseudopotential theory

Vora

2008

Open Physics

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Section: Resultsmentioning

confidence: 99%

Section: Theoretical Methodologymentioning

confidence: 99%

Section: Theoretical Methodologymentioning

confidence: 99%

Section: Theoretical Methodologymentioning

confidence: 99%

See 2 more Smart Citations

Study of superconducting state parameters of amorphous metals by a pseudopotential theory

Vora

2008

Open Physics

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“…One group of the models assumes the simultaneous presence of FM and antiferromagnetic (AF) exchange interactions in the Fe-rich amorphous Fe-Zr alloys, causing exchange frustration [6]. The reason for this assumption is that the Fe-Fe separation in these alloys is known to fluctuate around a value close to a critical Fe-Fe separation (d Fe = 2.55Å), where the direct exchange integral between the Fe atoms changes sign, strongly decreasing with decreasing Fe-Fe separation [7][8][9][10]. In this so-called wandering-axis ferromagnet model, the existence of a collinear FM matrix is questioned [5,11], and it is assumed that the spin structure is locally FM with small variation in neighboring spin directions; however, the local FM axis changes direction over distances of the order of 25Å.…”

Section: Introductionmentioning

confidence: 99%

Influence of the critical Fe atomic volume on the magnetism of Fe-rich metallic glasses evidenced by pressure-dependent measurements

et al. 2016

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Despite the intensive studies for decades, it is still not well understood how qualitatively different magnetic behaviors can occur in a narrow composition range for the Fe-rich Fe-transition metal (TM) amorphous alloys. In this study of amorphous Fe 100−x Zr x (x = 7, 9, 12) metallic glasses, normal ferromagnetism (FM) is found at 12 % Zr where only the FM-paramagnetic (PM) transition is observed at the Curie temperature, T C . In contrast, spin-glass (SG)-PM transition at a temperature, T g , called SG temperature, is only observed at 7 % Zr, while in the transient re-entrant composition range (x = 8−11), an SG-FM transition at a temperature, T f , called spin-freezing temperature, is also observed at low temperature besides the normal FM-PM transition at T C . In order to understand this unusual behavior, a detailed characterization of pressure (atomic volume), composition, and temperature dependence of the magnetic properties is coupled with high pressure synchrotron x-ray diffraction determination of the pressure dependence of the atomic volume. The results on Fe 100−x Zr x (x = 7, 9, 12) are compared to those obtained for the FM Co 91 Zr 9 metallic glass not showing any kind of anomalous magnetic properties. It is confirmed that the unusual behavior is caused by a granularlike magnetic structure where weakly coupled magnetic clusters are embedded into a FM bulk matrix. Since the mechanism of the magnetization reversal was found to be of the curling type rather than homogeneous rotation, the energy barrier determining the blocking temperature of the clusters is calculated as AR, where A is the exchange constant and R is the cluster size, in contrast to the usual characterization of the energy barrier by KV where K is the anisotropy energy and V is the cluster volume. The volume fraction of the FM part is a fast changing function of the bulk composition: Almost 100% FM fraction is found at 12 % of Zr while no trace of real FM is observed at 7 at % Zr. The driving force of this surprising magnetic character is the atomic volume: The lower the Zr content, the higher is the fraction of Fe atoms with compressed atomic volume having low magnetic moment. The percolation of their network separates the clusters from the FM bulk. The complex magnetic behavior of the Fe-rich Fe-Zr amorphous system at low temperatures can thus be interpreted with the only assumption of a cluster-size distribution and a weak coupling of the clusters to the FM matrix. The introduction of this coupling is able to explain the opposite pressure dependence of T g and T f . The threshold atomic volume in the low magnetic moment regions is found to be comparable to the atomic volume characteristic to the low-spin limit of the face-centered-cubic Fe alloys. The extensive literature results on the anomalous magnetism for various Fe-rich Fe-TM amorphous alloys and especially for the Fe-rich Fe-Zr glassy system are also found to be in agreement with this granular magnetic behavior.

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Disordered and Frustrated Spin Systems

Binder

Young

2007

Handbook of Magnetism and Advanced Magnetic Materials

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A brief review on the effects of quenched disorder on magnetic ordering is given. This disorder can be due to dilution of a ferro‐ or antiferromagnetic crystal with nonmagnetic atoms, or due to noncrystallinity (amorphous magnetic systems). This disorder in the positions of the magnetic atoms leads to disorder in the exchange interactions between spins. If the disorder is sufficiently weak, the critical temperature of magnetic ordering is somewhat decreased, and the critical behavior may change, but the nature of ordering is maintained. However, if the disorder is sufficiently strong, magnetic long‐range order may disappear altogether at a percolation threshold, or a new type of order may appear, the ‘spin glass’, in which spins freeze in random directions because of random competition between ferro‐ and antiferromagnetic interactions. In this context, we also mention magnetic systems with ‘frustration’ of their exchange interactions but without disorder. Finally, another important class of phenomena occurs for systems with ‘random fields’, an example of which is provided by diluted antiferromagnets in a uniform field.

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Physics of Amorphous Metals

Cited by 36 publications

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Study of superconducting state parameters of amorphous metals by a pseudopotential theory

Study of superconducting state parameters of amorphous metals by a pseudopotential theory

Influence of the critical Fe atomic volume on the magnetism of Fe-rich metallic glasses evidenced by pressure-dependent measurements

Disordered and Frustrated Spin Systems

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