Kohler Plot Research Articles

Tunable anomalous resistance and large magnetoresistance in HfTe5 by atom doping

The Dirac layered material HfTe5 renews significant interest due to its exotic band structure, leading to abundant transport properties, such as the anomaly resistance peak and its large magnetoresistance. Here, we prepared single crystals HfTe5 and Cr-doped CrxHf1−xTe5 and carried out their electrical transport measurements to explore the underlying physical origin of the anomaly resistance behavior and the large magnetoresistance. An anomalous resistance peak was observed in both intrinsic HfTe5 and the Cr-doped ones. Specifically, the peak temperature in the doped ones experiences an obvious shift from 52 to 34 K as the doping concentration x increases from 0 to 0.15, as well as the magnitude of the peak resistance is significantly enhanced. Furthermore, the magnetoresistance of CrxHf1−xTe5 is reduced by more than one order of magnitude compared with the intrinsic one. The significant reduction in magnetoresistance after Cr doping is attributed to the breaking of the balance between electron and hole carriers, which is confirmed by Kohler's plots. Meanwhile, in the sample where the magnetoresistance was minimized, we observed Shubnikov–de Haas oscillations. These observations illustrate that the large magnetoresistance is primarily contributed by the compensation of electrons and holes rather than the high mobility. Our findings provide valuable insight into how to engineer HfTe5 to achieve large magnetoresistance and its further applications in magnetic sensors and spintronics.

Low-temperature resistivity upturn and weak antilocalization in layered Ta1.04Ru0.78Te4 bulk single crystal

Quantum corrections to conductivity, which reflect charge carriers' quantum behavior, are a significant topic in condensed state physics and device design. A resistivity upturn at low temperature or weak antilocalization due to quantum corrections has been often observed experimentally. However, the coexistence of the low-temperature resistivity upturn and weak antilocalization from quantum corrections in bulk single crystals is seldom reported. Here, we report the transport properties of bulk Ta1.04Ru0.78Te4 single crystals. The samples showed a metallic behavior with a resistivity upturn below ∼8.6 K, which may be the result of quantum correction to the resistivity. The magnetic field enhances the upturn feature. The weakly nonlinear Hall resistivity with a positive slope suggests a p-type and multiband feature for bulk Ta1.04Ru0.78Te4; the electron and hole concentrations and mobilities of the samples are very close to each other and have the same order of magnitude. The Ta1.04Ru0.78Te4 single crystals displayed small and positive magnetoresistance, and the 3 K magnetoresistance at 9 T was about 15%. A lack of overlap of Kohler's plot curves at different temperature implies the violation of Kohler's rule. At low temperature, the dip-like magnetoresistance at low field strengths suggests a weak antilocalization in the Ta1.04Ru0.78Te4 single crystal. A small phase coherence length implies weakened screening and enhancing electron–electron interaction effects. These results reveal the quantum transport properties of Ta1.04Ru0.78Te4 single crystals, which can be considered in the future device design.

High-field magnetoresistance of microcrystalline and nanocrystalline Ni metal at 3 K and 300 K

The longitudinal and transverse magnetoresistance curves MR(H) and the magnetization isotherms M(H) were measured at T = 3 K and 300 K up to high magnetic fields for a microcrystalline (µc) Ni foil with grain sizes above 1 µm (corresponding to bulk Ni) and for a nanocrystalline (nc) Ni foil with an average grain size of about 100 nm. At T = 3 K, the field-induced resistivity change was quite different for the two microstructural states of Ni and the evolution of resistivity with magnetic field was also different which could be explained as arising from their very different electron mean free paths. At T = 300 K, the MR(H) curves of both the μc-Ni and nc-Ni samples were very similar to those known for bulk Ni. The MR(H) data were analyzed at both temperatures with the help of Kohler plots from which the resistivity anisotropy splitting (ΔρAMR) and the anisotropic magnetoresistance (AMR) ratio were derived, the latter values being very similar at both temperatures and for both microstructural states of Ni metal. The present high-precision MR(H) data revealed that the available theoretical models do not accurately describe the suppression of thermally induced magnetic disorder at around room temperature in high magnetic fields.

Magnetotransport and Berry phase in magnetically doped Bi0.97−xSb0.03 single crystals

We report large magnetoresistance (MR) and Shubnikov-de Haas (SdH) oscillations in single crystals of magnetically (M= Ni and Fe) doped M$_x$Bi$_{0.97-x}$Sb$_{0.03}$ ($x=$ 0, 0.02) topological insulators. The R$\bar{3}$m symmetry and phase have been confirmed by the Rietveld refinement of x-ray diffraction data. Interestingly, a magnetic field induced phase transition from semi-metallic to semi-conducting type is found with the energy gap around 80 meV at 15 Tesla in the $x=$ 0 sample. Moreover, we observe linear behavior of MR up to 15 Tesla in transverse mode and SdH oscillations in longitudinal mode where the field direction is with respect to the current and crystal plane. For the parent sample, we found the coherence length L$_\phi=$ 12.7 nm through the fitting of MR data in transverse mode with modified H-L-N equation. The extracted frequencies of SdH oscillations using the fast Fourier transform method and Landau level (LL) fan diagram are found to be consistent for the parent and Ni doped samples. The determined Fermi surface area is found to be slightly larger in Ni doped as compared to the parent sample possibly due to change in the Fermi energy. The Kohler's plot indicates a single scattering mechanism below 100 K. More importantly, the analysis with the help of LL fan diagram reveals the non-zero Berry phase $\phi_{\rm B}= -$(1$\pm$0.1)$\pi$, which demonstrates the non-trivial topological states near the Dirac point in the parent and Ni doped samples.

Anisotropy in the electronic transport properties of Weyl semimetal WTe2 single crystals

We measure the electrical resistivity ρ of type-II Weyl semimetal WTe2 using high-quality single crystals for the current I along the a and b crystallographic directions in rotating magnetic fields in the plane perpendicular to the current direction. In zero field, ρ exhibits huge anisotropy and the ratio ρb/ρa develops with decreasing temperature approaching ∼30 at T = 0. A low-T power-law behavior of ρ∝Tn with n = 2.7-2.9 may reflect the characteristic carrier scattering mechanism, probably associated with the strongly T-dependent mobilities, which lead to the sign change in the Hall resistivity. In the Kohler plot, the magnitude of the transverse magnetoresistance (MR) differs by more than two orders of magnitude depending on the I- and B-directions. It also shows clear deviation of MR from the B2 dependence for all the configurations. No singular directions (magic angles) appear in the rotating B measurements.

Deviation from the Kohler’s rule and Shubnikov–de Haas oscillations in type-II Weyl semimetal WTe2: High magnetic field study up to 56 T

We have measured magnetoresistance of type-II Weyl semimetal WTe2 in high magnetic fields of B//c up to B = 56 T using a high quality single crystal with the residual resistivity ratio 1330. A Kohler plot demonstrates the existence of a deviation from the B2 dependence. Significant deviation from Kohler’s rule appears with increasing temperature, indicating wave-vector k dependent anisotropic carrier scattering, which develops with increasing temperature. The fast-Fourier-transform spectra of the observed large-amplitude Shubnikov–de Haas oscillations confirm the existence of four fundamental and one additional (cyclotron frequency of 255 T) peaks. The amplitude of the latter one increases anomalously with increasing field, confirming this oscillation being due to magnetic breakdown (or magnetic breakthrough) between the two cyclotron orbits of the adjacent hole pockets.

Temperature dependence of magnetoresistance in copper single crystals

Transverse magnetoresistance of copper single crystals has been measured in the orientation of open-orbit from 2 K to 20 K for fields up to 9 T. The experimental Kohler's plots display deviation between individual curves below 16 K and overlap in the range of 16 K–20 K. The violation of the Kohler's rule below 16 K indicates that the magnetotransport can not be described by the classical theory of electron transport on spherical Fermi surface with a single relaxation time. A theoretical model incorporating two energy bands, spherical and cylindrical, with different relaxation times has been developed to describe the magnetoresistance data. The calculations show that the electron-phonon scattering rates at belly and neck regions of the Fermi surface have different temperature dependencies, and in general, they do not follow T3 law. The ratio of the relaxation times in belly and neck regions decreases parabolically with temperature as A−CT2, with A and C being constants.

Crystal growth and magneto-transport properties of α-ZrSb2 and α-HfSb2

We report the synthesis of single crystals of α-ZrSb2/α-HfSb2 and their magneto-transport properties. Both of α-ZrSb2 and α-HfSb2 exhibit metallic behavior. The T3 behavior of zero-field resistivity for both compounds below 30 K indicates interband electron-phonon scattering. The magnetoresistance (MR) is found to obey Kohler's rule for ZrSb2 while the MR of HfSb2 deviates from this rule. A possible explanation for the results of Kohler's plot is considered, which is confirmed with the results of the Hall effect. The positive linear Hall resistivity of ZrSb2 suggests hole-type carriers and a mobility of , while the existence of two types of carriers in HfSb2 is confirmed from the nonlinear Hall resistivity.

Crystal Growth and Magneto-transport of Bi2Se3 Single Crystals

In this letter, we report on the growth and characterization of bulk Bi 2Se 3 single crystals. The studied Bi 2Se 3 crystals are grown by the self-flux method through the solid-state reaction from high-temperature (950 °C) melt of constituent elements and slow cooling (2 ℃/h). The resultant crystals are shiny and grown in the [00l] direction, as evidenced from surface XRD. Detailed Reitveld analysis of powder X-ray diffraction (PXRD) of the crystals showed that these are crystallized in the rhombohedral crystal structure with a space group of R3m (D5), and the lattice parameters are a = 4.14 (2), b = 4.14 (2), and c = 28.7010 (7) A. Temperature versus resistivity (ρ−T) plots revealed metallic conduction down to 2 K, with typical room temperature resistivity (ρ 300 K) of around 0.53 m Ω-cm and residual resistivity (ρ 0 K) of 0.12 m Ω-cm. Resistivity under magnetic field [ ρ(T)H] measurements exhibited large + ve magneto-resistance right from 2 to 200 K. Isothermal magneto-resistance [ ρH] measurements at 2, 100, and 200 K exhibited magneto-resistance (MR) of up to 240 %, 130 %, and 60 %, respectively, at 14 T. Further, the MR plots are nonsaturating and linear with the field at all temperatures. At 2 K, the MR plots showed clear quantum oscillations at above say 10 T applied field. Also, the Kohler plots, i.e., Δρ/ ρ oversus B/ ρ, were seen consolidating on one plot. Interestingly, the studied Bi 2Se 3 single crystal exhibited the Shubnikov-de Haas (SdH) oscillations at 2 K under different applied magnetic fields ranging from 4 to 14 T.

The linear magnetoresistance from surface state of the Sb2SeTe2 topological insulator

A non-saturating linear magnetoresistance (MR) is observed in Sb2SeTe2 topological insulator. The results show that the MR slope and the critical magnetic field of the linear MR are proportional to the carrier mobility and inverse mobility, respectively. These are consistent with the prediction of a model, which is constructed by Parish and Littlewood [Nature 426, 162 (2003)], in the weak mobility fluctuation condition. The Kohler plot of the magnetoresistance does not collapse onto a single curve that supports the multi-carriers scattering mechanisms.

Influence of dislocation microstructure on low temperature magnetoresistance in copper single- and polycrystals

Angular and field dependent transverse magnetoresistance (TMR) have been studied in copper single- and polycrystals containing different density and distribution of dislocations. In the open-orbit orientation, the quadratic variation of TMR with the applied magnetic field changes to the quasi-linear dependence, as the density of dislocations increases. In the closed-orbit orientations, TMR shows a linear dependence with the magnetic field, the slope of the characteristic decreases with increasing the density of dislocations. The signatures of closed and extended orbits are preserved until the very high dislocation densities stored in the single crystals. The analysis of the Kohler's plots indicates that in the open-orbit orientation TMR violates Kohler's rule, but in the closed-orbit orientation Kohler's rule is obeyed. The results suggest that at low dislocation density, the magneto-transport of electrons is strongly anisotropic and is dominated by small-angle scattering, irrespective of the distribution of dislocations. In the crystals with higher densities of dislocations containing dislocation walls and cells, the electron transport is dominated by a high-angle scattering process. The magnetoresistance data are consistent with the two-band model and support the theory that the dislocation-induced relaxation time is anisotropic due to the non-sphericity of the Fermi surface. In the spherical portion of the Fermi surface the scattering is isotropic, associated with the constant relaxation time. Strongly anisotropic scattering in the aspherical portion of the Fermi surface is associated with a much smaller relaxation time.

RRR and thermal conductivity of Ag and Ag-0.2 wt.%Mg alloy in Ag/Bi-2212 wires

Residual resistivity ratio (RRR) and thermal conductivity of metal matrix in metal/superconductor composite wires are important parameters for designing superconducting magnets. However, the resistivity of silver in reacted Ag/Bi-2212 wires has yet to be determined over temperature range from 4.2 K to 80 K because Bi-2212 filaments have a critical transition temperature Tc of ∼ 80 K, and because it is unknown whether the RRR of Ag/Bi-2212 degrades with Cu diffusing from Bi-2212 filaments into silver sheathes at elevated temperatures and to what degree it varies with heat treatment. We measured the resistivity of stand-alone Ag and AgMg (Ag-0.2 wt.% Mg) wires as well as the resistivity of Ag and Ag-0.2 wt.% Mg in Ag/Bi- 2212 round wires reacted in 1 bar oxygen at 890 °C for 1, 8, 24 and 48 hours and quickly cooled to room temperature. The heat treatment was designed to reduce the critical current Ic of Bi- 2212 wires to nearly zero while allowing Cu loss to fully manifest itself. We determined that pure silver exhibits a RRR of ∼ 220 while the oxide-dispersion strengthened Ag-Mg exhibits a RRR of ∼ 5 in stand-alone samples. A surprising result is that the RRR of silver in the composite round wires doesn't degrade with extended time at 890 °C for up to 48 hours. This surprising result may be explained by our observation that the Cu that diffuses into silver tends to form Cu2O precipitates in oxidizing atmosphere, instead of forming Ag-Cu solution alloy. We also measured the thermal conductivity and the magneto-resistivity of pure Ag and Ag-0.2 wt. % Mg from 4.2 K to 300 K in magnetic fields up to 14.8 T and summarized them using a Kohler plot.

Charge Density Wave Transition in EuAl4

Charge Density Wave Transition in EuAl₄

Dominant role of impurity scattering over crystalline anisotropy for magnetotransport properties in the quasi-one-dimensional hollanditeBa1.2Rh8O16

Angular magnetotransport measurements have been performed to tackle the origin of the magnetoresistance in the quasi-one-dimensional hollandite ${\text{Ba}}_{1.2}{\text{Rh}}_{8}{\text{O}}_{16}$. Three samples of different impurities amount were measured. We observe that the low-temperature resistivity upturn is not due to a charge-density wave transition and a dominant role of impurities scattering for low-temperature transport properties is instead demonstrated. The components of magnetoresistance were separated by using the Kohler plot and the angular dependency of the resistance under magnetic field. It shows the major contribution of an isotropic, likely spin driven, negative magnetoresistance. Galvanomagnetic characteristics are then consistent with a Kondo effect and appear to be essentially three dimensional at low temperature.

Reply to French and Hussey: Evidence against orbital origin of field-induced quantum criticality in Tl 2 Ba 2 CuO 6+ x superconductors

In our recent article (1), we reported recovering Fermi-liquid features through quantum critical behavior in Tl2Ba2CuO6+x at high magnetic fields. French and Hussey (2) propose an alternative explanation for our results based entirely on orbital effects, assuming a temperature-dependent anisotropy of ωcτ in the basal plane. Their simulations show slight deviations in the Kohler's plot in their figure 1D. However, when compared with our experimental data (see Fig. 1) their extent of apparent violation is much smaller. This huge difference provides compelling evidence that the orbital origin cannot explain our experimental observations quantitatively.

Hump Like Resistance Anomaly in Organic Conductor β''-(BEDT-TTF)2CsCd(SCN)4

We investigate the low-temperature electronic phase of a two-dimensional organic conductor, β''-(BEDT-TTF) 2 CsCd(SCN) 4 [where BEDT-TTF denotes bis(ethylenedithio)tetrathiafulvalene], which has a large hump between 32 and around 5 K in the temperature dependence of the interlayer resistance. We present experimental results for the temperature dependence of the resistance under magnetic fields and its Kohler plots, and an x-ray diffraction study. We find that I) Kohler's rule is strongly violated below 32 K, although the rule is valid above 32 K, and II) weak superlattice spots appear at 15.6 K in the x-ray study. On the basis of the experimental results, we suggest that the origin of the resistance hump is the formation of a possible charge density wave transition at about 32 K by the nesting of a pair of large one-dimensional Fermi surfaces obtained in the electronic structure calculation based on the crystal structure at room temperature.

Transverse magnetoresistance of oxygen-free copper

Recent studies on the magnetoresistance of copper with residual resistance ratios (RRR) in the range 100-1000, and using cold work and irradiation as parameters modifying RRR, show a large spread when presented on a Kohler plot. Results of 4 K magnetoresistance measurements on a large number of samples of copper from various sources and in various states of cold work, strain, and reanneal are presented and discussed. The RRR values range from 48 to 655; all tempers are represented. The results shown suggest that use of Kohler plot data taken at 4 K to predict magnetoresistance at much higher temperatures (such as 76 K) is probably not a reliable practice.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Anisotropy in the Hall coefficient of indium

The Hall coefficient of single-crystal indium was measured in two geometries: B//(100)(RH perpendicular to ) and B//(001)(RH//) at 4.2K. An anisotropy was observed in the Kohler plot: in intermediate and low fields, RH perpendicular to is more negative than RH//. Isothermal measurements of RH at 3.5K and 1.9K are also reported. The effects of the Fermi surface geometry and the wavenumber-dependent electronic relaxation time on the anisotropy are discussed.

Transverse Resistivity of (TMTSF)2PF6 and (TKTSF)2ClO4 in a Magnetic Field, Evidence for Kohler's Rule

Abstract We report data for the c* axis resistivity of (TMTSF)2PF6 and (TMTSF)2ClO4 in magnetic fields of up to 70 kilogauss. The results are analysed in the form of Kohler's plots. Deviations from Kohler's rule can be used to detect the onset of magnetic ordering at low temperatures. In the PF6 salt there are also deviations at higher temperatures which may be due to the breakdown of the band description of electron states.

133. Kohler's plots for the magnetoresistance of highly oriented graphite

133. Kohler's plots for the magnetoresistance of highly oriented graphite