Hole doping and antiferromagnetic correlations above the N\'eel temperature of the topological semimetal $({\mathrm{Sr}}_{1\ensuremath{-}x}{\mathrm{K}}_{x}){\mathrm{MnSb}}_{2}$

Hole doping and antiferromagnetic correlations above the Néel temperature of the topological semimetal $({Sr}_{1 - x} K_{x}) {MnSb}_{2}$

Yong Liu, Farhan Islam, Kevin W. Dennis, Wei Tian, Benjamin G. Ueland, Robert J. McQueeney, and David Vaknin

Phys. Rev. B 100, 014437 – Published 29 July 2019

Abstract

Neutron diffraction and magnetic susceptibility studies of orthorhombic single crystal $({Sr}_{0.97} K_{0.03}) {MnSb}_{2}$ confirm the three-dimensional (3D) C-type antiferromagnetic (AFM) ordering of the ${Mn}^{2 +}$ moments at $T_{N} = 305 \pm 3$ K, which is slightly higher than that of the parent ${SrMnSb}_{2}$ with $T_{N} = 297 \pm 3$ K. Susceptibility measurements of the K-doped and parent crystals above $T_{N}$ are characteristic of 2D AFM systems. This is consistent with high-temperature neutron diffraction of the parent compound that displays persisting 2D AFM correlations well above $T_{N}$ to at least $\sim 560$ K with no evidence of a ferromagnetic phase. Analysis of the de Haas–van Alphen magnetic oscillations of the K-doped crystal is consistent with hole doping.

Received 3 May 2019

DOI:https://doi.org/10.1103/PhysRevB.100.014437

Physics Subject Headings (PhySH)

Magnetism Topological materials

Neutron scattering

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Yong Liu^1,*, Farhan Islam¹, Kevin W. Dennis¹, Wei Tian², Benjamin G. Ueland^1,3, Robert J. McQueeney^1,3, and David Vaknin ^1,3,†

¹Division of Materials Sciences and Engineering, Ames Laboratory, U.S. DOE, Ames, Iowa 50011, USA
²Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
³Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA

^*Present address: Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China and Dongguan Neutron Science Center, Dongguan 523803, China.
^†vaknin@ameslab.gov

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Vol. 100, Iss. 1 — 1 July 2019

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Figure 1
XRD patterns displaying the $(H 00)$ reflections up to the 22nd order for both crystals by using Cu $K α$ radiation, shown on a logarithmic scale. Weak extra peaks for $({Sr}_{0.97} K_{0.03}) {MnSb}_{2}$ crystals, indicated by the asterisk, could not be matched with known impurity phases unequivocally.
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Figure 2
(a) Zero-field-cooled (ZFC) magnetic susceptibility, $χ \equiv M / H$ , of single crystals ${SrMnSb}_{2}$ and $({Sr}_{0.97} K_{0.03}) {MnSb}_{2}$ with applied magnetic field along the $a$ -axis $(χ_{a})$ for ${SrMnSb}_{2}$ and $({Sr}_{0.97} K_{0.03}) {MnSb}_{2}$ indicating a slight increase in $T_{N}$ upon K-substitution. The inset shows $d χ (T) / d T$ vs $T$ with peaks at $T_{N}$ that coincide with neutron diffraction extracted $T_{N}$ 's. The K-substituted single crystal exhibits a slightly higher $T_{N}$ than the parent compound. (b) ZFC susceptibility at high temperatures (above $T_{N})$ for the parent and the doped crystals with magnetic field aligned in the $b c$ plane. The increase in susceptibility above the $T_{N}$ and the broad peak are common signatures of 2D magnetic systems that develop large correlations prior to the 3D ordering, which can be driven by negligible interplane coupling. The inset shows the same measurements to higher temperatures that indicate a chemical change, presumably at the surface, that generates ferromagnetic impurity. The inset also shows the susceptibility while cooling from the high temperature with a new superimposed FM component with $T_{c} \approx 560$ K. (c) Magnetization vs applied magnetic field at room temperature before and after heating the $({Sr}_{0.97} K_{0.03}) {MnSb}_{2}$ sample used for the measurement shown in (b).
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Figure 3
(a) Comparison of the FT of the oscillating $M_{a} (B)$ for the parent ${SrMnSb}_{2}$ and the K-substituted $({Sr}_{0.97} K_{0.03}) {MnSb}_{2}$ . The inset shows $Δ M_{a} (1 / H)$ for both crystals as indicated. (b) Enumerating peak and valleys in (a) as a function of $1 / H$ (assigning integers to minima). The intercepts at $n (1 / H \to 0) = 0.76 (6)$ and 0.72(9) for both crystals as indicated.
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Figure 4
Intensity of magnetic Bragg reflections (a) (010) and (001) and (b) (030) and (003) vs momentum transfer for the stoichiometric single crystal ${SrMnSb}_{2}$ below and above $T_{N}$ . As is evident, the crystal is, to a large extent, not twinned. (c) The intensity of magnetic Bragg reflections (a) (010) for $({Sr}_{0.97} K_{0.03}) {MnSb}_{2}$ below and above $T_{N}$ as indicated. (d) The intensities vs temperature of the magnetic (010) including a fit (solid line) to a power law $I \propto {(1 - T / T_{N})}^{2 β}$ yield $T_{N} = 297 (2)$ and 305(4) K and $β = 0.227 (2)$ and 0.173(3) for the pure and K-doped crystals $[({Sr}_{0.97} K_{0.03}) {MnSb}_{2}]$ , respectively. The inset illustrates atomic chemical and magnetic structure.
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Figure 5
(a) Magnetic Bragg reflection (010) at 80 K along with quasielastic scattering at 313 and 481 K (the intensities of peaks above $T_{N}$ are multiplied by a factor of 500). The FWHM of the peaks above $T_{N}$ suggests an upper limit for the average 2D correlations at 80 Å. (b) Temperature dependence of the integrated intensity of the (010) peak over the extended temperature range (on a semilogarithmic scale) showing the persistence of magnetic scattering to the highest temperature measured with no indication of a transition up to $\sim 575$ K.
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Physical Review B

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Hole doping and antiferromagnetic correlations above the Néel temperature of the topological semimetal $({Sr}_{1 - x} K_{x}) {MnSb}_{2}$

Yong Liu, Farhan Islam, Kevin W. Dennis, Wei Tian, Benjamin G. Ueland, Robert J. McQueeney, and David Vaknin

Phys. Rev. B 100, 014437 – Published 29 July 2019

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Physical Review B

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Hole doping and antiferromagnetic correlations above the Néel temperature of the topological semimetal (Sr1−xKx)MnSb2

Yong Liu, Farhan Islam, Kevin W. Dennis, Wei Tian, Benjamin G. Ueland, Robert J. McQueeney, and David Vaknin

Phys. Rev. B 100, 014437 – Published 29 July 2019

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Hole doping and antiferromagnetic correlations above the Néel temperature of the topological semimetal $({Sr}_{1 - x} K_{x}) {MnSb}_{2}$