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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.

No MeSH data available.


First-principle electronic structure of NbSb2.(a) The total density of states (DOS), as well as the contribution to DOS from different atoms (Nb, Sb1 and Sb2), (b) the band structure and (c) the Fermi surfaces of NbSb2 crystals from first-principle calculation. The spin-orbit coupling was taking into account in process. For clarity the orientation of the hole pockets (the upper panel in (c)) is rotated in comparison to the electron pockets (the lower panel in (c)). The red rectangle in (b) indicates the area where the conduction band touches the valence band at the Fermi level. The binding energy for FS is 0.6482 eV.
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f4: First-principle electronic structure of NbSb2.(a) The total density of states (DOS), as well as the contribution to DOS from different atoms (Nb, Sb1 and Sb2), (b) the band structure and (c) the Fermi surfaces of NbSb2 crystals from first-principle calculation. The spin-orbit coupling was taking into account in process. For clarity the orientation of the hole pockets (the upper panel in (c)) is rotated in comparison to the electron pockets (the lower panel in (c)). The red rectangle in (b) indicates the area where the conduction band touches the valence band at the Fermi level. The binding energy for FS is 0.6482 eV.

Mentions: The Hall resistivity confirms the multiband characteristic of NbSb2. Fig. 3(c) shows the ρxy(B) in different temperatures with the current parallel to b-axis and the magnetic field perpendicular to the current. At 2 K, ρxy is initially positive below 1 T but changes to negative in higher fields. With increasing temperature, the field where ρxy changes the sign increases but achieves the maximum (8.5 T) in ~150 K. Further increase in the temperature above 150 K induces the decrease of the sign reversal field (Fig. 3(d)). The curvature and sign reversal of the Hall resistivity clearly indicates the coexistence of two types of carriers in NbSb2. This is in agreement with the sign change in Seebeck coefficient in (T,B) (inset in Fig. 3(d)) and with the electronic structure from the first-principles calculation (Fig. 4) which also shows hole and electron pockets. The density of states (DOS) (Fig. 4(a)) reveals that the Fermi level of NbSb2 locates at the valley of the DOS. This is confirmed by the band structure (Fig. 4(b)). In the band structure (Fig. 4(b)), there are two Dirac-like points across the Fermi level, along the M − H and Γ − Z line respectively. The Fermi level (EF) is located in the valley of these two bands, so both contribute somewhat to the density of state at the Fermi level. This is consistent with the nearly vanishing density of states near EF and the states at the Fermi level are dominated by Nb contribution. The FS of NbSb2 consists of electron pocket and hole pocket with different size (Fig. 4(c)), which is consistent with the two oscillation frequencies (two peaks in Fig. 3(a)). Even though most of the pockets are three-dimensional, there is an electron pocket which is anisotropic at the center of the Brillouin zone and it should dominate the anisotropic magnetoresistance in NbSb2.


Anisotropic giant magnetoresistance in NbSb2.

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

First-principle electronic structure of NbSb2.(a) The total density of states (DOS), as well as the contribution to DOS from different atoms (Nb, Sb1 and Sb2), (b) the band structure and (c) the Fermi surfaces of NbSb2 crystals from first-principle calculation. The spin-orbit coupling was taking into account in process. For clarity the orientation of the hole pockets (the upper panel in (c)) is rotated in comparison to the electron pockets (the lower panel in (c)). The red rectangle in (b) indicates the area where the conduction band touches the valence band at the Fermi level. The binding energy for FS is 0.6482 eV.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f4: First-principle electronic structure of NbSb2.(a) The total density of states (DOS), as well as the contribution to DOS from different atoms (Nb, Sb1 and Sb2), (b) the band structure and (c) the Fermi surfaces of NbSb2 crystals from first-principle calculation. The spin-orbit coupling was taking into account in process. For clarity the orientation of the hole pockets (the upper panel in (c)) is rotated in comparison to the electron pockets (the lower panel in (c)). The red rectangle in (b) indicates the area where the conduction band touches the valence band at the Fermi level. The binding energy for FS is 0.6482 eV.
Mentions: The Hall resistivity confirms the multiband characteristic of NbSb2. Fig. 3(c) shows the ρxy(B) in different temperatures with the current parallel to b-axis and the magnetic field perpendicular to the current. At 2 K, ρxy is initially positive below 1 T but changes to negative in higher fields. With increasing temperature, the field where ρxy changes the sign increases but achieves the maximum (8.5 T) in ~150 K. Further increase in the temperature above 150 K induces the decrease of the sign reversal field (Fig. 3(d)). The curvature and sign reversal of the Hall resistivity clearly indicates the coexistence of two types of carriers in NbSb2. This is in agreement with the sign change in Seebeck coefficient in (T,B) (inset in Fig. 3(d)) and with the electronic structure from the first-principles calculation (Fig. 4) which also shows hole and electron pockets. The density of states (DOS) (Fig. 4(a)) reveals that the Fermi level of NbSb2 locates at the valley of the DOS. This is confirmed by the band structure (Fig. 4(b)). In the band structure (Fig. 4(b)), there are two Dirac-like points across the Fermi level, along the M − H and Γ − Z line respectively. The Fermi level (EF) is located in the valley of these two bands, so both contribute somewhat to the density of state at the Fermi level. This is consistent with the nearly vanishing density of states near EF and the states at the Fermi level are dominated by Nb contribution. The FS of NbSb2 consists of electron pocket and hole pocket with different size (Fig. 4(c)), which is consistent with the two oscillation frequencies (two peaks in Fig. 3(a)). Even though most of the pockets are three-dimensional, there is an electron pocket which is anisotropic at the center of the Brillouin zone and it should dominate the anisotropic magnetoresistance in NbSb2.

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.