Uniaxial pressure effect on the magnetic ordered moment and transition temperatures in ${\mathrm{BaFe}}_{2\ensuremath{-}x}{T}_{x}{\mathrm{As}}_{2}$ ($T=\text{Co},\text{Ni}$)

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Uniaxial pressure effect on the magnetic ordered moment and transition temperatures in ${BaFe}_{2 - x} T_{x} {As}_{2}$ ( $T = Co, Ni$ )

David W. Tam, Yu Song, Haoran Man, Sky C. Cheung, Zhiping Yin, Xingye Lu, Weiyi Wang, Benjamin A. Frandsen, Lian Liu, Zizhou Gong, Takashi U. Ito, Yipeng Cai, Murray N. Wilson, Shengli Guo, Keisuke Koshiishi, Wei Tian, Bassam Hitti, Alexandre Ivanov, Yang Zhao, Jeffrey W. Lynn, Graeme M. Luke, Tom Berlijn, Thomas A. Maier, Yasutomo J. Uemura, and Pengcheng Dai

Phys. Rev. B 95, 060505(R) – Published 17 February 2017

Abstract

We use neutron diffraction and muon spin relaxation to study the effect of in-plane uniaxial pressure on the antiferromagnetic (AF) orthorhombic phase in ${BaFe}_{2} {As}_{2}$ and its Co- and Ni-substituted members near optimal superconductivity. In the low-temperature AF ordered state, uniaxial pressure necessary to detwin the orthorhombic crystals also increases the magnetic ordered moment, reaching an 11% increase under 40 MPa for ${BaFe}_{1.9} {Co}_{0.1} {As}_{2}$ , and a 15% increase for ${BaFe}_{1.915} {Ni}_{0.085} {As}_{2}$ . We also observe an increase of the AF ordering temperature ( $T_{N}$ ) of about 0.25 K/MPa in all compounds, consistent with density functional theory calculations that reveal better Fermi surface nesting for itinerant electrons under uniaxial pressure. The doping dependence of the magnetic ordered moment is captured by combining dynamical mean field theory with density functional theory, suggesting that the pressure-induced moment increase near optimal superconductivity is closely related to quantum fluctuations and the nearby electronic nematic phase.

Received 1 July 2016
Revised 4 January 2017

DOI:https://doi.org/10.1103/PhysRevB.95.060505

Physics Subject Headings (PhySH)

Antiferromagnetism Superconductivity

Neutron diffraction

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

David W. Tam¹, Yu Song¹, Haoran Man¹, Sky C. Cheung², Zhiping Yin³, Xingye Lu¹, Weiyi Wang¹, Benjamin A. Frandsen², Lian Liu², Zizhou Gong², Takashi U. Ito⁴, Yipeng Cai⁵, Murray N. Wilson⁵, Shengli Guo⁶, Keisuke Koshiishi⁷, Wei Tian⁸, Bassam Hitti⁹, Alexandre Ivanov¹⁰, Yang Zhao^11,12, Jeffrey W. Lynn¹¹, Graeme M. Luke⁵, Tom Berlijn¹³, Thomas A. Maier¹³, Yasutomo J. Uemura², and Pengcheng Dai^1,3,*

¹Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA
²Department of Physics, Columbia University, New York, New York 10027, USA
³Center for Advanced Quantum Studies and Department of Physics, Beijing Normal University, Beijing 100875, China
⁴Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
⁵Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada L8S 4M1
⁶Department of Physics, Zhejiang University, Hangzhou 310027, China
⁷Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-Ku, Tokyo 113, Japan
⁸Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
⁹TRIUMF, Vancouver, British Columbia, Canada V6T2A3
¹⁰Institut Laue-Langevin, 71 avenue des Martyrs, 38000 Grenoble, France
¹¹NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
¹²Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA
¹³Center for Nanophase Materials Sciences and Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6494, USA

^*pdai@rice.edu

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Vol. 95, Iss. 6 — 1 February 2017

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Figure 1
(a), (b) Real-space and $Q$ -space configurations in the AF state, showing the majority-domain Bragg reflections $Q_{strong} = (\pm 1, 0)$ in red dots for pressure applied along the $b$ axis, and the minority-domain Bragg reflections $Q_{weak} = (0, \pm 1)$ as blue dots. (c), (d) Schematic illustration of the uniaxial-pressure-induced Fermi surface distortion parallel to the $a b$ plane (at $k_{z} = 0.375 π / c$ ) for (c) ${BaFe}_{2} {As}_{2}$ and (d) ${BaFe}_{1.915} {Ni}_{0.085} {As}_{2}$ . Arrows indicate the direction of distortion in this $k_{z}$ plane for the uniaxially strained case, which is much smaller than the thickness of the markers. Coloring shows the dominant orbital character as indicated in the inset. (e) Experimental phase diagram of ${BaFe}_{2 - x} {Ni}_{x} {As}_{2}$ [47]. (f) Electron-doping dependence of the ordered magnetic moment with ( $M$ , red) and without ( $M_{0}$ , purple) uniaxial pressure obtained from a combined DFT/DMFT calculation. The inset shows $δ = (a - b) / (a + b)$ dependence of $M / M_{0}$ at $x = 0$ , 0.05, and 0.1. (g) Theoretical/experimental results demonstrating the enhancement of $Δ M / M$ as $M$ decreases on approaching optimal doping [11]. (h) Enhancement of $Δ T_{N} / T_{N}$ , as $T_{N}$ decreases on approaching optimal doping.
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Figure 2
(a) Intensity change of the $Q_{strong} = (1, 0, 5)$ peak with uniaxial pressure on ${BaFe}_{2} {As}_{2}$ at IN8. (b) Detwinning ratio $η = (I_{strong} - I_{weak}) / (I_{strong} + I_{weak})$ for both HB-1A and IN8 experiments, and the total intensity (circles) $I_{strong} + I_{weak}$ at IN8 which remains conserved, up to small corrections that we attribute to the extinction effect. (c), (d) Rocking curves at $(1, 0, 5)$ and $(0, 1, 5)$ measured at IN8 at $T = 90$ K, demonstrating nearly 100% detwinning above 10 MPa. The solid lines are fits to a single Gaussian peak. (e) Temperature dependence of $Q_{strong} = (1, 0, 1)$ on warming. For clarity, the vertical scale of each scan has been slightly adjusted to represent the total magnetic scattering intensity, using the integrated intensity of a rocking scan measured immediately prior to warming. (f) Shift in AF ordering temperature $Δ T_{N} = T_{N}^{(P)} - T_{N}^{(P = 0)}$ ( $T_{N}^{(P = 0)} \approx 140$ K) for ${BaFe}_{2} {As}_{2}$ [11].
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Figure 3
(a) Intensity change of $Q_{strong} = (1, 0, 3)$ with uniaxial pressure on ${BaFe}_{1.915} {Ni}_{0.085} {As}_{2}$ at HB-1A. (b) Shift in AF ordering temperature $Δ T_{N} = T_{N}^{(P)} - T_{N}^{(P = 0)}$ ( $T_{N}^{(P = 0)} \approx 35$ K). (c) Rocking curves at $Q_{strong} = (1, 0, 3), T = 20$ K, measured at HB-1A in the $[H, 0, L]$ scattering plane. (d) Temperature scans at HB-1A. The dashed line indicates the superconducting region ( $T_{c}^{(40} MPa) - T_{c}^{(0)} \approx - 3 K$ ) [11]. (e) Temperature dependence of the magnetic scattering intensity at $Q_{strong} = (1, 0, 3)$ and $Q_{weak} = (0, 1, 3)$ with and without pressure, measured in situ at BT-7. (f) Combined rocking scans at $(1, 0, 3)$ and $(0, 1, 3)$ . Data at 60 K have been subtracted from each $Q$ position before combining the data. (g) Fast muon relaxation rate $λ$ [11]. (h) Fast-relaxing fraction $V_{M}$ , demonstrating constant magnetic sample volume for all pressures below 35 K.
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Figure 4
(a) Increase of the oscillation frequency in the fast-relaxing portion of the muon decay asymmetry, for $T = 2$ K (superconducting), 25 K, and 45 K for ${BaFe}_{1.9} {Co}_{0.1} {As}_{2}$ [11]. (b) Muon decay asymmetry at 25 K as a function of uniaxial pressure. The fraction of muons remaining polarized in this short-time window are those landing in the nonmagnetic sample holder. (c) Fast-relaxing fraction of muons in a 30 G transverse magnetic field, demonstrating a constant magnetic sample volume below $T_{N} = 65$ K, as well as a broadening of the magnetic transition under pressure and an increase in $T_{N}$ . (d) Data in (a) plotted as an order parameter.
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Uniaxial pressure effect on the magnetic ordered moment and transition temperatures in ${BaFe}_{2 - x} T_{x} {As}_{2}$ ( $T = Co, Ni$ )

Phys. Rev. B 95, 060505(R) – Published 17 February 2017

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Uniaxial pressure effect on the magnetic ordered moment and transition temperatures in BaFe2−xTxAs2 (T=Co,Ni)

Phys. Rev. B 95, 060505(R) – Published 17 February 2017

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Uniaxial pressure effect on the magnetic ordered moment and transition temperatures in ${BaFe}_{2 - x} T_{x} {As}_{2}$ ( $T = Co, Ni$ )