Hallov efekt u amorfnim slitinama ranih i kasnih prijelaznih metala

We present a detailed analysis of the available data for the Hall effect and its dependence on composition, electrical resistivity and temperature in disordered alloys of early and late transition metals. The systems analysed include amorphous binary Zr-(Co,Ni,Cu), Ta-Ni, Ti-Cu, W-Cu and ternary TE-TL-M alloys (TE = Zr or Ti, TL = Ni or Cu and M = Al or Ga). The results for amorphous La-Ga and liquid Ce-Cu alloys are also included. The dependence of the Hall coefficient on composition, electrical resistivity and temperature indicate that the Hall effect in these systems consists of the normal and anomalous (magnetic) Hall effects that are almost of the same order of magnitude. It is shown that the anomalous contribution is the cause why the Hall effect becomes positive for early transition metal rich amorphous alloys.Prikazana je detaljna analiza dostupnih podataka za Hallov efekt i njegovu ovisnost o sastavu, električnoj otpornosti i temperaturi u neuređenim slitinama na bazi ranih i kasnih prijelaznih metala. Prikazani su rezultati za amorfne binarne Zr- (Co,Ni,Cu), Ta-Ni, Ti-Cu, W-Cu i ternarne TE-TL-M slitine (TE = Zr ili Ti, TL = Ni ili Cu, i M = Al ili Ga). Priloženi su i rezultati za amorfne La-Ga i tekuće Ce-Cu slitine. Iz ovisnosti Hallovog koeficijenta o sastavu, električnoj otpornosti i temperaturi, zaključili smo da je Hallov efekt u tim sistemima zbroj normalnog i anomalnog (magnetskog) doprinosa. Anomalni Hallov efekt je istog reda veličine kao i normalni i on je uzrok pozitivnog ukupnog Hallovog koeficijenta svojstvenog za amorfne slitine na bazi ranih prijelaznih metala

Two-dimensional vortex plasma in Bi_2Sr_2CaCu_2O_x single crystals in the vicinity of T_c

Quantitative analysis of results of measurements of magnetoresistance of Bi_2Sr_2CaCu_2O_x single crystals for magnetic fields 0.2-0.8 T, in the temperature interval 78.5-84 K has been made. For temperatures lower than 81 K the dissipation is predominantly determined by the suppression of the long-range superconducting order, whereas closer to T_c the flux-flow contribution becomes significant. We obtain very good agreement between the experiment and the model in which two dissipation mechanisms are additive

Dvodimenzionalna plazma magnetskih vrtloga u monokristalima Bi2Sr2CaCu20x u blizini Tc

Quantitative analysis of results of measurements of magnetoresistance of Bi2Sr2CaCu2Ox single crystals for magnetic fields 0.2-0.8 T, in the temperature interval 78.5-84 K has been made. For temperatures lower than 81 K the dissipation is predominantly determined by the suppression of the long-range superconducting order, whereas closer to Tc the flux-flow contribution becomes significant. We obtain very good agreement between the experiment and the model in which two dissipation mechanisms are additive.Izvršili smo kvantitativnu analizu magnetootpora monokristala Bi2Sr2CaCu2Ox, za magnetska polja 0.2–0.8 T i u temperaturnom području 78.5–84 K. Na temperaturama ispod 81 K disipacija je uglavnom posljedica potiskivanja dugodosežnog supravodljivog uređenja, dok bliže Tc doprinos kretanja vrtloga postaje značajan. Ustanovljeno je vrlo dobro slaganje eksperimentalnih rezultata i modela u kojem su ta dva disipacijska mehanizma aditivna

Hall Coefficient of the Y-Al-Ni-Co Decagonal Approximant

We have investigated anisotropic Hall coefficient of Y-Al-Ni-Co decagonal approximant of the Al76Co22Ni2 composition. The crystalline-direction-dependent studies were performed along three orthogonal directions a*, b and c of the Y-Al-Ni-Co unit cell, where (a,c) monoclinic atomic planes are stacked along the perpendicular b direction. Hall coefficient RH exhibits pronounced anisotropy, while at the same time the magnetic field in a given crystalline direction yields the same RH for the current along the other two crystalline directions in the perpendicular plane. The observed anisotropy is studied in terms of the anisotropic structure of the Y-Al-Ni-Co phase and Fermi surface. The results are compared to the anisotropy of the Hall coefficient of the d-Al-Ni-Co decagonal quasicrystal reported in literature.</p

Hall Effect of the Al13Fe4 Decagonal Approximant and Its Ternary Extension Al13(Fe,Ni)4

We have measured Hall coefficient and electrical resistivity of the Al13Fe4 and Al13(Fe,Ni)4 monoclinic approximants to the decagonal quasicrystal. While the Al13Fe4 crystals are structurally well ordered, the ternary extension Al13(Fe,Ni)4 contains quenched disorder and can be viewed as a disordered version of Al13Fe4. The crystallographic-direction-dependent Hall effect measurements were performed along the a*, b and c directions of the monoclinic unit cell, where (a*,c) atomic planes are stacked along the perpendicular b direction. The stacking b direction is the most conducting direction for the electricity. The effect of quenched disorder in Al13(Fe,Ni)4 is manifested in the large residual resistivity ρ(T → 0) as compared to the ordered Al13Fe4. The Hall coefficient, RH, values for all combinations of directions, are typical metallic. The anisotropic Hall coefficient reflects complicated structure of the anisotropic Fermi surface that contains electron-like and hole-like parts. Depending on the combination of directions of the current and magnetic field electron-like (RH 0) contributions may dominate, or the two contributions compensate each other (RH ≈ 0).</p

Two-dimensional vortex plasma in Bi_2Sr_2CaCu_2O_x single crystals in the vicinity of T_c

Quantitative analysis of results of measurements of magnetoresistance of Bi_2Sr_2CaCu_2O_x single crystals for magnetic fields 0.2-0.8 T, in the temperature interval 78.5-84 K has been made. For temperatures lower than 81 K the dissipation is predominantly determined by the suppression of the long-range superconducting order, whereas closer to T_c the flux-flow contribution becomes significant. We obtain very good agreement between the experiment and the model in which two dissipation mechanisms are additive

Anisotropic Transport Properties of the Orthorhombic Al13Co4 Approximant to the Decagonal Quasicrystal

Anisotropic transport properties (electrical resistivity, thermoelectric power, Hall coefficient and thermal conductivity) of the o-Al13Co4 orthorhombic approximant to the decagonal phase were investigated. The crystalline-direction-dependent measurements were performed along the a, b and c directions of the orthorhombic unit cell, where (b, c) atomic planes are stacked along the perpendicular a direction. Anisotropic electrical and thermal conductivities are the highest along the stacking a direction. The anisotropic thermoelectric power changes sign with the crystalline direction and so does the anisotropic Hall coefficient, which changes from the negative electron-like to the positive hole-like for different combinations of the electric current and magnetic field direction. The transport properties of the o-Al13Co4 phase were compared to the literature data on approximant to the decagonal quasicrystals, the Al76Co22Ni2 and the Al80Cr15Fe5, allowing for the study of evolution of transport properties with increasing structural complexity and unit cell size.</p

Hall Effect of the Triclinic Al73Mn27 and T-Al73Mn27–xPdx (0 ≤ x ≤ 6) Complex Metallic Alloys

The Hall coefficient, RH, of the triclinic Al73Mn27 and Taylor-phase Al73Mn27xPdx (x = 0, 2, 4 and 6) complex metallic alloys has been measured from 90 to 400 K. The Hall coefficients of all the samples are positive and they decrease strongly with the increase of temperature, T. For the separation of the normal, R0, and anomalous, RS, Hall coefficient the results for the paramagnetic susceptibility,χ(T), and electrical resistivity, ρ(T), have been used. The well defined linearity of the RH vs. χ(T)·ρ2(T) plots confirms the assumption that in these materials RH is dominated by spin-orbit interaction. The values deduced from the RH vs. χ and RH vs. χ·ρ2 plots in T­AlMnPd phases, fall between –2 × 10–10 m3 C–1 and 0 for R0, and are about 5 × 10–7 m3 C–1 for RS. The values deduced from the RH vs. χ·ρ2 plots in the triclinic Al73Mn27 alloy are about –15 × 10–10 m3 C–1 for R0, and about 1.5 × 10–5 m3 C–1 for RS.</p