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Anisotropic giant magnetoresistance in NbSb2.

Wang K, Graf D, Li L, Wang L, Petrovic C - Sci Rep (2014)

Bottom Line: The magnetic field response of the transport properties of novel materials and then the large magnetoresistance effects are of broad importance in both science and application.Magnetoresistance is significantly suppressed but the metal-semiconductor-like transition persists when the current is along the ac-plane.The large MR is attributed to the change of the Fermi surface induced by the magnetic field which is related to the Dirac-like point, in addition to orbital MR expected for high mobility metals.

View Article: PubMed Central - PubMed

Affiliation: Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973 USA.

ABSTRACT
The magnetic field response of the transport properties of novel materials and then the large magnetoresistance effects are of broad importance in both science and application. We report large transverse magnetoreistance (the magnetoresistant ratio ~ 1.3 × 10(5)% in 2 K and 9 T field, and 4.3 × 10(6)% in 0.4 K and 32 T field, without saturation) and field-induced metal-semiconductor-like transition, in NbSb2 single crystal. Magnetoresistance is significantly suppressed but the metal-semiconductor-like transition persists when the current is along the ac-plane. The sign reversal of the Hall resistivity and Seebeck coefficient in the field, plus the electronic structure reveal the coexistence of a small number of holes with very high mobility and a large number of electrons with low mobility. The large MR is attributed to the change of the Fermi surface induced by the magnetic field which is related to the Dirac-like point, in addition to orbital MR expected for high mobility metals.

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Quantum Oscillation and Hall resistivity of NbSb2.(a) The FFT spectrum of the quantum oscillation of NbSb2 crystal. The inset shows the typical SdH oscillation of NbSb2 in 0.42 K with magnetic field up to 32 T. The current is parallel to b-axis and the magnetic field direction changes between perpendicular to the current (parallel to the ac-plane 0 degree) and perpendicular to ac-plane (90 degree). (b) The temperature dependence of the quantum oscillation amplitude for two oscillation frequencies. The blue lines are the fit results which give the effective mass. The inset shows the magnetic field dependence of the oscillation at different temperatures. (c) The magnetic field dependence of the Hall resistivity ρxy at different temperatures. (d) Sign change of Hall coefficient at different temperatures and magnetic fields. The inset shows the temperature dependence of the Seebeck coefficient S with different magnetic field.
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f3: Quantum Oscillation and Hall resistivity of NbSb2.(a) The FFT spectrum of the quantum oscillation of NbSb2 crystal. The inset shows the typical SdH oscillation of NbSb2 in 0.42 K with magnetic field up to 32 T. The current is parallel to b-axis and the magnetic field direction changes between perpendicular to the current (parallel to the ac-plane 0 degree) and perpendicular to ac-plane (90 degree). (b) The temperature dependence of the quantum oscillation amplitude for two oscillation frequencies. The blue lines are the fit results which give the effective mass. The inset shows the magnetic field dependence of the oscillation at different temperatures. (c) The magnetic field dependence of the Hall resistivity ρxy at different temperatures. (d) Sign change of Hall coefficient at different temperatures and magnetic fields. The inset shows the temperature dependence of the Seebeck coefficient S with different magnetic field.

Mentions: In monoclinic phase of NbSb2, the bond length of Nb-Nb is about 3.6Å along the b-axis and is about 5.4Å and 4.9Å along the a and c axis respectively. This indicates that NbSb2 is formed by quasi-one-dimensional Nb chains along the b direction (Fig. 1(a) and Ref. 41). Fig. 3(a) and (b) shows the results of the Shubnikov-de Haas (SdH) oscillation for NbSb2 crystals where the current is along b-axis but the field direction changes between parallel to the ac-plane (perpendicular to b-axis, θ = 0°) and perpendicular to ac-plane (θ = 90°). The MR of NbSb2 shows clear oscillations above 8 T field (inset in Fig. 3(a)), and the oscillation is very clear in the whole angle range implying dominant 3D FS. The MR does not saturate even in 35 T field. Instead it shows the quantum oscillations where MR approaches 4.3 × 106% in 0.4 K and 32 T field [Fig. 3(a) inset]. The fast Fourier transformation (FFT) spectrum of oscillation (Fig. 3(a)) shows two major peaks at 227 T and 483 T oscillation frequency. In metal or semiconductor, the SdH oscillations correspond to successive emptying of Landau levels and the corresponding periodic singularity in the density of states as the magnetic field is increased. In quantum oscillation, the period or the frequency, when plotted against 1/B (B is the magnetic field), is inversely proportional to the area S of the extremal orbit of the Fermi surface, in the direction of the applied field. For a general system, the oscillatory part of the magnetoresistance (described as magnetoconductivity Δσ) is given by where the frequency Fi of the quantum oscillation is proportional to the extremal area Ai of the i-th Fermi pocket in the direction of the magnetic field and can be described as . The two oscillation frequencies (two peaks in the FFT spectrum, Fig. 3(a)) observed in NbSb2 clearly indicate the existence of two Fermi pockets which are of different size. Besides, the temperature dependence of the oscillation amplitude is given by the thermal factor RT in the above equation and is described by the Lifshitz-Kosevitch formula The temperature dependence of the oscillation amplitude (Fig. 3(b)) can be fitted well by the Lifshitz-Kosevitch formula26, which gives the effective cyclotron resonant mass m* = 0.68me and 1.69me (me is the mass of bare electron) for 227 T and 483 T Fermi pockets respectively.


Anisotropic giant magnetoresistance in NbSb2.

Wang K, Graf D, Li L, Wang L, Petrovic C - Sci Rep (2014)

Quantum Oscillation and Hall resistivity of NbSb2.(a) The FFT spectrum of the quantum oscillation of NbSb2 crystal. The inset shows the typical SdH oscillation of NbSb2 in 0.42 K with magnetic field up to 32 T. The current is parallel to b-axis and the magnetic field direction changes between perpendicular to the current (parallel to the ac-plane 0 degree) and perpendicular to ac-plane (90 degree). (b) The temperature dependence of the quantum oscillation amplitude for two oscillation frequencies. The blue lines are the fit results which give the effective mass. The inset shows the magnetic field dependence of the oscillation at different temperatures. (c) The magnetic field dependence of the Hall resistivity ρxy at different temperatures. (d) Sign change of Hall coefficient at different temperatures and magnetic fields. The inset shows the temperature dependence of the Seebeck coefficient S with different magnetic field.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4256591&req=5

f3: Quantum Oscillation and Hall resistivity of NbSb2.(a) The FFT spectrum of the quantum oscillation of NbSb2 crystal. The inset shows the typical SdH oscillation of NbSb2 in 0.42 K with magnetic field up to 32 T. The current is parallel to b-axis and the magnetic field direction changes between perpendicular to the current (parallel to the ac-plane 0 degree) and perpendicular to ac-plane (90 degree). (b) The temperature dependence of the quantum oscillation amplitude for two oscillation frequencies. The blue lines are the fit results which give the effective mass. The inset shows the magnetic field dependence of the oscillation at different temperatures. (c) The magnetic field dependence of the Hall resistivity ρxy at different temperatures. (d) Sign change of Hall coefficient at different temperatures and magnetic fields. The inset shows the temperature dependence of the Seebeck coefficient S with different magnetic field.
Mentions: In monoclinic phase of NbSb2, the bond length of Nb-Nb is about 3.6Å along the b-axis and is about 5.4Å and 4.9Å along the a and c axis respectively. This indicates that NbSb2 is formed by quasi-one-dimensional Nb chains along the b direction (Fig. 1(a) and Ref. 41). Fig. 3(a) and (b) shows the results of the Shubnikov-de Haas (SdH) oscillation for NbSb2 crystals where the current is along b-axis but the field direction changes between parallel to the ac-plane (perpendicular to b-axis, θ = 0°) and perpendicular to ac-plane (θ = 90°). The MR of NbSb2 shows clear oscillations above 8 T field (inset in Fig. 3(a)), and the oscillation is very clear in the whole angle range implying dominant 3D FS. The MR does not saturate even in 35 T field. Instead it shows the quantum oscillations where MR approaches 4.3 × 106% in 0.4 K and 32 T field [Fig. 3(a) inset]. The fast Fourier transformation (FFT) spectrum of oscillation (Fig. 3(a)) shows two major peaks at 227 T and 483 T oscillation frequency. In metal or semiconductor, the SdH oscillations correspond to successive emptying of Landau levels and the corresponding periodic singularity in the density of states as the magnetic field is increased. In quantum oscillation, the period or the frequency, when plotted against 1/B (B is the magnetic field), is inversely proportional to the area S of the extremal orbit of the Fermi surface, in the direction of the applied field. For a general system, the oscillatory part of the magnetoresistance (described as magnetoconductivity Δσ) is given by where the frequency Fi of the quantum oscillation is proportional to the extremal area Ai of the i-th Fermi pocket in the direction of the magnetic field and can be described as . The two oscillation frequencies (two peaks in the FFT spectrum, Fig. 3(a)) observed in NbSb2 clearly indicate the existence of two Fermi pockets which are of different size. Besides, the temperature dependence of the oscillation amplitude is given by the thermal factor RT in the above equation and is described by the Lifshitz-Kosevitch formula The temperature dependence of the oscillation amplitude (Fig. 3(b)) can be fitted well by the Lifshitz-Kosevitch formula26, which gives the effective cyclotron resonant mass m* = 0.68me and 1.69me (me is the mass of bare electron) for 227 T and 483 T Fermi pockets respectively.

Bottom Line: The magnetic field response of the transport properties of novel materials and then the large magnetoresistance effects are of broad importance in both science and application.Magnetoresistance is significantly suppressed but the metal-semiconductor-like transition persists when the current is along the ac-plane.The large MR is attributed to the change of the Fermi surface induced by the magnetic field which is related to the Dirac-like point, in addition to orbital MR expected for high mobility metals.

View Article: PubMed Central - PubMed

Affiliation: Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973 USA.

ABSTRACT
The magnetic field response of the transport properties of novel materials and then the large magnetoresistance effects are of broad importance in both science and application. We report large transverse magnetoreistance (the magnetoresistant ratio ~ 1.3 × 10(5)% in 2 K and 9 T field, and 4.3 × 10(6)% in 0.4 K and 32 T field, without saturation) and field-induced metal-semiconductor-like transition, in NbSb2 single crystal. Magnetoresistance is significantly suppressed but the metal-semiconductor-like transition persists when the current is along the ac-plane. The sign reversal of the Hall resistivity and Seebeck coefficient in the field, plus the electronic structure reveal the coexistence of a small number of holes with very high mobility and a large number of electrons with low mobility. The large MR is attributed to the change of the Fermi surface induced by the magnetic field which is related to the Dirac-like point, in addition to orbital MR expected for high mobility metals.

No MeSH data available.


Related in: MedlinePlus