Hall effect measurements on epitaxial SmNiO${}_{3}$ thin films and implications for antiferromagnetism

Hall effect measurements on epitaxial SmNiO $_{3}$ thin films and implications for antiferromagnetism

Sieu D. Ha, R. Jaramillo, D. M. Silevitch, Frank Schoofs, Kian Kerman, John D. Baniecki, and Shriram Ramanathan

Phys. Rev. B 87, 125150 – Published 29 March 2013

Abstract

The rare-earth nickelates ( $R$ NiO $_{3}$ ) exhibit interesting phenomena such as unusual antiferromagnetic order at wave vector q $=$ (½, 0, ½) and a tunable insulator-metal transition that are subjects of active research. Here we present temperature-dependent transport measurements of the resistivity, magnetoresistance, Seebeck coefficient, and Hall coefficient ( $R_{H}$ ) of epitaxial SmNiO $_{3}$ thin films with varying oxygen stoichiometry. We find that from room temperature through the high temperature insulator-metal transition, the Hall coefficient is holelike and the Seebeck coefficient is electronlike. At low temperature the Néel transition induces a crossover in the sign of $R_{H}$ to electronlike, similar to the effects of spin density wave formation in metallic systems but here arising in an insulating phase ∼200 K below the insulator-metal transition. We propose that antiferromagnetism can be stabilized by band structure even in insulating phases of correlated oxides, such as $R$ NiO $_{3}$ , that fall between the limits of strong and weak electron correlation.

Received 22 October 2012

DOI:https://doi.org/10.1103/PhysRevB.87.125150

Authors & Affiliations

Sieu D. Ha^1,*,†, R. Jaramillo^1,†, D. M. Silevitch², Frank Schoofs¹, Kian Kerman¹, John D. Baniecki³, and Shriram Ramanathan¹

¹School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
²The James Franck Institute and Department of Physics, The University of Chicago, Chicago, Illinois 60637, USA
³Fujitsu Laboratories, Atsugi 243-0197, Japan

^*Corresponding author: sdha@seas.harvard.edu
^†These two authors contributed equally.

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Vol. 87, Iss. 12 — 15 March 2013

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Figure 1
(a) Phase diagram of $R$ NiO $_{3}$ . See Refs. 6, 7, and 8 for selected source data. (b) Hall resistance $R_{x y}^{'}$ at select temperatures for SNO3, showing linearity and crossover in the sign of $R_{H}$ below $T_{N}$ ∼ 180 K. (c) AFM micrograph of SNO2 showing atomic steps (0.379 nm) of LaAlO $_{3}$ (001) substrate. (d) XRD φ scans from SNO1 at (011) pseudocubic reflection of LaAlO $_{3}$ and (221) orthorhombic reflection of SmNiO $_{3}$ . (e) Unit cell volume of SmNiO $_{3}$ grown on LaAlO $_{3}$ as a function of total sputtering pressure.Reuse & Permissions
Figure 2
ρ( $T$ ) for SNO1, SNO2, and SNO3 showing the effects of varying oxygen stoichiometry. Oxygen content is monotonically decreased from SNO1 to SNO3. Inset: $d$ (ln ρ)/ $d T$ , where the anomalous kink marks $T_{N}$ .Reuse & Permissions
Figure 3
(a) Transverse magnetoresistance $M R$ ( $H$ ) ≡ [ρ( $H$ ) − ρ(0)]/ρ(0) at select temperatures for SNO3. Data are collected in full ±90 kOe field sweeps; the component even in $H$ is extracted and plotted here. (b) $M R$ (90 kOe) as a function of temperature for SNO2 and SNO3. $M R$ < 0 and $M R$ > 0 data are shown on separate logarithmic plots. (1) and (2) denote distinct regimes of negative $M R$ . (c) Seebeck coefficient measured on SNO2 showing electronlike majority carriers in insulating and metallic phases above room temperature.Reuse & Permissions
Figure 4
$R_{H}$ ( $T$ ) for SNO1, SNO2, and SNO3. The crossover in sign tracks the evolution of $T_{N}$ with oxygen stoichiometry. Inset: $R_{H}$ ( $T$ ) and ρ( $T$ ) for PrNiO $_{3}$ with $T_{IM}$ $=$ $T_{N}$ marked. Reprinted from Ref. 13, Copyright 1994, with permission from Elsevier.Reuse & Permissions
Figure 5
(a) Estimated hole and electron carrier densities and (b) Hall mobilities for SNO1, SNO2, and SNO3 in and near the metallic regime extracted from Hall coefficient data. Transport data are calculated assuming $μ_{p}$ $=$ $μ_{n}$ $=$ μ and $p$ $+$ $n$ $=$ $K$ , a constant. The hatched area represents the likely breakdown of the assumptions for $T$ < $T_{IM}$ (see text).Reuse & Permissions
Figure 6
(a) Fermi surface of LaNiO $_{3}$ . The holelike cube (blue) is shown in the left panel; the right panel shows both the electronlike pocket (red) and the holelike surfaces in a side view projection, with the calculated nesting vector illustrated. Adapted with permission from Ref. 9. Copyrighted by the American Physical Society. Short dashed line is cut along which dispersion is plotted in lower panel. (b) and (c) Schematic of dispersion along a short line crossing the nested Fermi surface as the temperature is lowered sequentially through $T_{IM}$ and $T_{N}$ . (b) Dispersion for $T$ > $T_{IM}$ (solid line) and $T_{IM}$ > $T$ > $T_{N}$ (dotted line) for a generic insulating band gap. Occupied states are lowered in energy by $E_{g}$ /2, as illustrated by the gray filling, and unoccupied states are raised. (c) Dispersion for $T_{IM}$ > $T$ > $T_{N}$ (dotted line) and $T_{N}$ > $T$ (dashed line) for 2Δ $_{SDW}$ / $E_{g}$ $=$ 2. The energy of the occupied states at $k$ $=$ ¼ is not lowered by the full Δ $_{SDW}$ , but the overall energy lowering (gray filling) may be significant.Reuse & Permissions

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