The decrease in electrical resistivity with temperature and the weak magnetic behavior of these alloys are the subjects of this study. The electrical resistivity of Pd-Cu-P has been measured from 4.2°K to Tc, the crystallization temperature of the alloys {rv 525°K). The magnetic susceptibility of the alloys has been measured over the temperature range 4.2 to 300°K using a Faraday magnetic balance apparatus.
The construction and design of the magnet system was done by Oxford Instrument Company, England. 2 Variable temperature cryostat insert. the insert is monitored by an Au-0.03 at.% Fe/chromel thermocouple whose reference compound is in the outer helium bath. Pd100_xCux)100-ypy was measured over a temperature range from 4°K to Tg', the crystallization temperature of the alloys (rv 550°K).
Second, the resistivity was measured from room temperature to above the crystallization temperature of the alloys. The linear decrease of resistance with temperature up to Tq (rv 550°K) and the dependence of temperature coefficients of resistance on composition 1 during crystallization are interesting. The decrease in resistance with temperature observed at high temperatures is also seen at low temperatures.
The main temperature dependence of the resistance has been interpreted as being due to the temperature dependence of a(k), as discussed by Sinha. Boucher's measurement of the dependence of the resistance behavior on phosphorus concentration is very interesting. 33 the results of Boucher's measurements of the room temperature values of p and a are plotted.
TEMPERATURE (°K)
For metal-like Pd, if we denote the density of states at the Fermi level in the d-band by N(O) and the intraatomic Coulomb interaction between two electrons in the same unit cell by V. 0 , then the simple Hartree-Fock theory (16} shows that sensitivity of the metal greater than the Pauli sensitivity of free electrons by a factor of [1- V -1.0), then we can expect a region of space near the Ni cell much closer to magnetic instability than in the Pd matrix.
The S electrons, which in Pd carry the majority of the current, can be scattered from these local spin fluctuations. For example, in the AlCr and AlMn alloys studied by Caplin and Rizzuto(lB), the low-temperature resistance goes as p = p. However, it is very difficult to imagine that the spin-fluctuation model holds at all in the Pd-Cu-P alloys, and even its application to Pd-Ni-P and Pt-Ni-P alloys leaves certain experiments unexplained. facts.
For the Pd-Cu-P alloys, the use of the spin-fluctuation model encounters an obvious difficulty: Cu cannot serve to enhance the local intra-atomic Coulomb interaction, as Ni is supposed to do for Pd-Ni-P and Pt- ~i-P alloys . The experimental results on Pd-Cu-P indicate:. the temperature coefficient of resistivity and the resistivity are quite sensitive to variations in the Cu concentration; the temperature. resistivity coefficients are all negative for alloys with x > 15, and the temperature dependence of resistivity is quite similar in shape for the Pd-Ni-P and Pt-Ni-P alloys. The comparison we have made of the Pd-Cu-P data with the systems Pt-Ni-P and Pd-Ni-P points out the relevance of this work to previous studies of amorphous materials.
Both the structural dispersion model proposed by Sinha and the spin-fluctuation model proposed by Hasegawa have inherent difficulties when applied to the resistivity behavior of the amorphous alloys Pt-Ni-P, Pd-Ni-P and Pd-Cu-P and yet, in a general sense, the temperature dependence of the electrical. This common behavior of these amorphous materials will be shown to be shared with numerous crystalline transition metal alloys in the following section. The recognition of this fact leads quite naturally to an explanation of the electrical properties of these materials.
Despite these structural variations, no influence of the phase changes on the measured resistivity is observable, and a remains at 100 x 10-6oK-l for 60 < x < 80. In a 11 the a 11 oys 1 is indicated as the The weak temperature dependence of resistivity persists at low temperatures, with exceptions for systems involving order-disorder transitions. Any explanation for this behavior based on the structural dependence on the d-band structure is certainly ruled out due to the variety of structures involved in the Mooij correlation.
36 reveals a remarkable agreement of data for amorphous alloys with those for many crystalline transition metal alloys surveyed by ~1ooij. An alternative explanation of the resistance behavior of Pd-Cu-P, Pd-Ni-P and Pt-Ni-P amorphous alloy is given along the following lines. First the order of magnitude of resistance for these connections is explained using the Evans, Greenwood and Lloyd (EGL) formula.
38 Schematic diagram of the parameters a(K) and Tlz involved in determining the electrical resistance in liquid transition metals. A schematic diagram of the interaction between the structural scattering (as determined by the a(2KF) factor) and the resonance scattering (as determined by n2) is shown in Figure 38. In light of the strong similarities in the structural scattering of the For amorphous alloys, this substitution is a good approximation.
This reduced density of states is also consistent with the low value of the Pauli paramagnetism observed in the Pd-Cu-P, Pd-Ni-P and Pt-Ni-P alloys. However, it is possible to show, based on the assumption that the transition metal-glass-forming interactions fix the value of the ~ = 2 phase shift n. Thus the difference in the concentration dependence of the Pd-Cu-P alloys on changes in metal.
The increase in p with phosphorus concentration in these alloys seems to indicate a marked sensitivity of the resonance parameters to the glass concentration. This is due to the hybridization of the d states of the transition metal to form strong bonds with the glass-forming atoms. On the contrary, the highly disordered nature of these alloys (also structurally disordered, since they are amorphous alloys according to the Mooi correlation) suggests that the larger effect—phononic modification of the density of states—is more effective in determining the temperature. dependence on.
The combined effects on the perturbation resistance of the density of states from. the electron-phonon interaction and the subsequent displacement of the EF as a result of this blurring are clearly shown in Figs. The observed susceptibility level of these bonds can be compared to the strong paramagnetism of crystalline Pd (x = . 5.3 x l0- 6 emu/gm). These indications make the use of the electron transfer model to explain the reduced sensitivity in amorphous Pd-Ni-P, Pt-Ni-P and Pd-Cu-P alloys difficult to justify.
An alternative explanation of the level of resistivity, the concentration dependence of resistivity, and the observed negative temperature coefficients of resistivity have been given. The method is based on the Evans, Greenwood and Lloyd formulation for the electrical resistivity of liquid transition metals and alloys and the phonon-induced modification of the density of.
