Magnetic structure and spin fluctuations in the colossal magnetoresistance ferrimagnet ${\mathrm{Mn}}_{3}{\mathrm{Si}}_{2}{\mathrm{Te}}_{6}$

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Magnetic structure and spin fluctuations in the colossal magnetoresistance ferrimagnet ${Mn}_{3} {Si}_{2} {Te}_{6}$

Feng Ye, Masaaki Matsuda, Zachary Morgan, Todd Sherline, Yifei Ni, Hengdi Zhao, and G. Cao

Phys. Rev. B 106, L180402 – Published 1 November 2022

Abstract

The ferrimagnetic insulator ${Mn}_{3} {Si}_{2} {Te}_{6}$ , which features a Curie temperature $T_{c}$ at 78 K and a delicate yet consequential magnetic frustration, exhibits colossal magnetoresistance (CMR) when the magnetic field is applied along the magnetic hard axis, surprisingly inconsistent with existing precedents [Y. Ni, H. Zhao, Y. Zhang, B. Hu, I. Kimchi, and G. Cao, Phys. Rev. B 103, L161105 (2021)]. This discovery motivates a thorough single-crystal neutron diffraction study in order to gain insights into the magnetic structure and its hidden correlation with the new type of CMR. Here we report a noncollinear magnetic structure below the $T_{c}$ where the moments lie predominantly within the basal plane but tilt toward the $c$ axis by $\approx 10^{\circ}$ at ambient conditions. A substantial magnetic diffuse scattering decays slowly and persists well above the $T_{c}$ . The evolution of the spin correlation lengths agrees well with the electrical resistivity, underscoring the role of spin fluctuation contributing to the magnetoresistivity near the transition. Application of magnetic field along the $c$ axis renders a swift occurrence of CMR but only a slow tilting of the magnetic moments toward the $c$ axis. The unparalleled changes indicate a nonconsequential role of magnetic polarization.

Received 17 May 2022
Revised 15 August 2022
Accepted 18 October 2022

DOI:https://doi.org/10.1103/PhysRevB.106.L180402

Physics Subject Headings (PhySH)

Colossal magnetoresistance Magnetism

Neutron diffraction

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Feng Ye ^1,*, Masaaki Matsuda ¹, Zachary Morgan ¹, Todd Sherline ¹, Yifei Ni ², Hengdi Zhao ², and G. Cao ²

¹Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
²Department of Physics, University of Colorado at Boulder, Boulder, Colorado 80309, USA

^*yef1@ornl.gov

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Vol. 106, Iss. 18 — 1 November 2022

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Figure 1
(a) The refined zero-field magnetic structure of ${Mn}_{3} {Si}_{2} {Te}_{6}$ at 5 K. Two symmetry inequivalent Mn sites are located at $(1 / 3, 2 / 3, z)$ with $z \approx 0$ and $1 / 4$ . The spin directions are dominantly along the [1,0,0] direction and $\approx 10^{\circ}$ tilting away from the basal plane. The pathways of the first three AFM exchange interactions $J_{1} \approx - 402, J_{2} \approx - 73$ , and $J_{3} \approx - 172$ K/Mn [12] between neighboring magnetic ions are also shown in cyan, blue, and red arrows. (b) The magnetic structure projected in the basal plane. $a_{m}, b_{m}$ , and $c_{m}$ are the axes in the monoclinic setting. (c) The $T$ dependence of the (1,0,0) peak associated with the canted spin configuration. Inset: Comparison of the wave-vector scan at 10 and 120 K across the (1,0,0) Bragg peak. (d) The $T$ dependence of the dominant (0,0,2) magnetic peak for the ferrimagnetic spin order.
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Figure 2
(a) The contour plot of the neutron diffraction data in the $(H, H, L)$ scattering plane collected on CORELLI at 5 K with 200-K data subtracted as background. (b) The similar plot at 100 K. (c) Wave-vector scans along the [1,0,0] direction across the magnetic (0,0,2) peak at selected temperatures. The solid lines are the Lorentzian fits to the data points. (d) Left: The $T$ dependence of the peak intensities at $Q = (- 0.025, 0, 2)$ . The dashed line is the fit to the data points using exponential decay form $I (T) = A_{1} e^{- (T - T_{0}) / t_{1}} + I_{0}$ , with $T_{0} = 79 (1), t_{1} = 16.3 (5), A_{1} = 3800 (20)$ , and $I_{0} = 1720 (15)$ . Right: The thermal evolution of in-plane resistivity $ρ_{a b} (T)$ (solid purple line) and $ξ_{a b}^{2} (T)$ , where $ξ_{a b}$ (blue solid square) is in-plane correlation length.
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Figure 3
Field dependence of the (a) (0,1,1) and (b) (0,1,0) magnetic reflections with field direction parallel to the $c$ axis. Solid blue and red lines for $μ_{0} H > 1$ T are the calculated intensities with angle tilting smoothly from $10^{\circ}$ to $33^{\circ}$ . The inset of (b) illustrates the conversion of three equally populated magnetic twins into a single domain at field $\approx$ 1 T. (c) The field dependence of the in-plane lattice constant $a$ at 5 K. The temperature dependence of peak intensity of the (d) (0,1,1) and (e) (0,1,0) peaks at a field of 4.75 T. Dashed lines are guides to the eye.
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Figure 4
(a) Field dependence of the in-plane resistivity $ρ_{a b}$ (purple) and canted angle obtained from neutron diffraction and magnetization measurements. (b) $T$ dependence of the (0,0,2) magnetic reflection as a function of increasing in-plane electric current. (c) The in situ measurement of resistance under the same experimental configuration. Inset: The setup that performs simultaneous neutron diffraction and electric transport measurement.
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Physical Review B

covering condensed matter and materials physics

Magnetic structure and spin fluctuations in the colossal magnetoresistance ferrimagnet ${Mn}_{3} {Si}_{2} {Te}_{6}$

Feng Ye, Masaaki Matsuda, Zachary Morgan, Todd Sherline, Yifei Ni, Hengdi Zhao, and G. Cao

Phys. Rev. B 106, L180402 – Published 1 November 2022

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Physical Review B

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Magnetic structure and spin fluctuations in the colossal magnetoresistance ferrimagnet Mn3Si2Te6

Feng Ye, Masaaki Matsuda, Zachary Morgan, Todd Sherline, Yifei Ni, Hengdi Zhao, and G. Cao

Phys. Rev. B 106, L180402 – Published 1 November 2022

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Magnetic structure and spin fluctuations in the colossal magnetoresistance ferrimagnet ${Mn}_{3} {Si}_{2} {Te}_{6}$