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Slow spin dynamics and quantum tunneling of magnetization in the dipolar antiferromagnet DyScO3

N. D. Andriushin, S. E. Nikitin, G. Ehlers, and A. Podlesnyak
Phys. Rev. B 106, 104427 – Published 23 September 2022
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  • INTRODUCTION
  • RESULTS AND ANALYSIS
  • DISCUSSION AND CONCLUSION
  • ACKNOWLEDGMENTS
  • APPENDICES
    • References

    Abstract

    We present a comprehensive study of static and dynamic magnetic properties in the Ising-like dipolar antiferromagnet (AFM) DyScO3 by means of DC and AC magnetization measurements supported by classical Monte Carlo calculations. Our AC-susceptibility data show that the magnetic dynamics exhibit a clear crossover from an Arrhenius-like regime to quantum tunneling of magnetization (QTM) at T*=10K. Below TN=3.2K, DyScO3 orders in an antiferromagnetic GxAy-type magnetic structure and the magnetization dynamics slow down to the minute timescale. The low-temperature magnetization curves exhibit complex hysteretic behavior, which depends strongly on the magnetic field sweep rate. We demonstrate that the low-field anomalies on the magnetization curve are related to the metamagnetic transition, while the hysteresis at higher fields is induced by a strong magnetocaloric effect. Our theoretical calculations, which take into account dipolar interaction between Dy3+ moments, reproduce essential features of the magnetic behavior of DyScO3. We demonstrate that DyScO3 represents a rare example of an inorganic compound, which exhibits QTM at a single-ion level and magnetic order due to classical dipolar interaction.

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    • Received 27 April 2022
    • Revised 20 July 2022
    • Accepted 22 August 2022

    DOI:https://doi.org/10.1103/PhysRevB.106.104427

    ©2022 American Physical Society

    Physics Subject Headings (PhySH)

    1. Research Areas
    Magnetic susceptibilitySpin dynamics
    1. Physical Systems
    Antiferromagnets
    1. Techniques
    Monte Carlo methods
    Condensed Matter, Materials & Applied Physics

    Authors & Affiliations

    N. D. Andriushin1,*, S. E. Nikitin2, G. Ehlers3, and A. Podlesnyak4

    • 1Institut für Festkörper- und Materialphysik, Technische Universität Dresden, D-01069 Dresden, Germany
    • 2Quantum Criticality and Dynamics Group, Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland
    • 3Neutron Technologies Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
    • 4Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA

    • *Corresponding author: Nikita.Andriushin@tu-dresden.de

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    Issue

    Vol. 106, Iss. 10 — 1 September 2022

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    Images

    • Figure 1
      Figure 1

      Crystal (a) and magnetic (b) structure of DyScO3. Red, green, and violet balls represent O2−, Sc3+, and Dy3+ ions, respectively. Red and light blue arrows represent arrangement of Dy moments at two neighbor layers for GxAy spin configuration [28]. (c) Sketch of the energy diagram of J=15/2 multiplet of Dy3+ in DyScO3, shown in |MJ〉−E coordinates. Spin-orbit coupling (SOC) produces the J=15/2 multiplet, which is split into 8 doublets by CEF. The ground state doublet consists of |±15/2〉 wave functions, following by excited |±13/2〉, |±11/2〉, etc. While the temperature dependence of the spin excitation associated with |±15/2〉→|±13/2〉 transition follows Arrhenius law, the direct transition between |±15/2〉 states is the temperature-independent QTM process.

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    • Figure 2
      Figure 2

      Temperature dependencies of the magnetization of DyScO3 measured using VSM at B=0.1T (a) and calculated by Monte Carlo (b) with different temperature sweep rates as described in Sec. 2c. Red and blue lines represent data collected on warming and cooling, respectively. Data are in (a) and (b) are shifted respectively by +0.5 μB/f.u. and +1 μB/f.u. vertically for clarity.

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    • Figure 3
      Figure 3

      Temperature dependence of real (a) and imaginary (b) parts of the complex longitudinal AC susceptibility of DyScO3 measured with 5 Oe drive field for f=1,10,100Hz and 2.5 Oe for 1000 Hz applied along [010] at zero DC field. The static spin susceptibility M/B measured at B=0.1T using VSM is shown in (a). Crossed black lines in (b) illustrate how the crossover temperatures was determined for f=10,100, and 1000 Hz curves.

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    • Figure 4
      Figure 4

      Frequency dependence of the AC susceptibility measured at multiple temperatures between 2 and 20 K. (a) and (b) show the real [χ′(f)] and imaginary [χ′′(f)] parts of the AC susceptibility, respectively. (c) shows the Cole-Cole plot χ′′(χ′). All data are shown with a constant vertical offset for clarity.

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    • Figure 5
      Figure 5

      Time dependence of magnetization taken after switching off 0.01 T magnetic field. Color dots and black lines in panel (a) show experimental data and relaxation calculated with ILT. (b) Relaxation time distribution function calculated for T=1.8K curve using different regularization parameter α as detailed in legend. (c) Relaxation time distribution function calculated for α=10 and different temperatures.

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    • Figure 6
      Figure 6

      Arrhenius plot log(f)(1/T), reconstructed from our results along with data from Ref. [35]. The grey dotted line shows the transition temperature TN. The blue and green points show the peak positions extracted from the frequency and temperature dependencies of imaginary part of AC susceptibility χ′′, and the black squares show the high-frequency data from Ref. [35]. Red solid line shows the calculated CEF activation curve with experimentally determined Δ=290K. Red points show inverse relaxation constants 1/τ extracted as positions of probability density maximum calculated with the ILT.

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    • Figure 7
      Figure 7

      Magnetization curves M(B) measured at several temperatures as indicated at each panel. The curves were measured with different sweep field rates as shown in legend.

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    • Figure 8
      Figure 8

      AFM ordering at zero field. (a) Temperature dependence of (001) Bragg peak. Red dots represent experimental data extracted from neutron powder diffraction [28]. Orange dots show data obtained by single-crystal neutron diffraction on TASP instrument. The solid line is the result of Monte Carlo calculations. (b) Calculated and measured low-temperature specific heat. The nuclear contribution was approximated by C(T)=βT3 with β=0.23 mJ mole−1K−4 and added to the calculated curve. The nuclear contribution reaches 0.047 J mole−1K−1 at T=6K and therefore is barely visible at this temperature scale. (c) Temperature dependence of the correlation length measured by neutron diffuse scattering (red and pink dots) [28] and calculated by Monte Carlo (blue and light blue dots). The filled area represents the estimated uncertainty of the calculation. (d) Simulated neutron diffraction pattern in the (H0L) scattering plane calculated at TN<T=3.5K showing anisotropic diffuse scattering around the primary AFM peak (001). (e) Neutron scattering intensity of (001) peak measured at multiple temperatures using TASP instrument. (f) Neutron scattering intensity of (001) peak at 2 K, measured along (H00) direction.

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    • Figure 9
      Figure 9

      [(a1)–(c1)] The magnetization curves calculated taking into account magnetocaloric effect at various temperatures of reservoir and corresponding system temperature dependence. The magnetization curves were calculated for external field ramped from zero to 2 T and backward, the shaded areas show width of the hysteresis curves ΔM(B)=M(B)↑−M(B)↓. Additional panels (a2)–(c2) show temperature change during simulation, grey horizontal lines denote reservoir temperatures. Reservoir temperatures are indicated in each panel. The contour map (d) is the calculated magnetic structural factor for the incommensurate state around B=0.4T and T=1K [red circle at (c1)].

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    • Figure 10
      Figure 10

      Protocol used for magnetization relaxation measurements. Orange and blue points show time dependence of magnetic field and magnetization collected at T=1.8 K.

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    • Figure 11
      Figure 11

      Calculated and experimental AC susceptibility at T=4K.

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    • Figure 12
      Figure 12

      (a) Calculated magnetic part of the heat capacity as function of external field and temperature. (b) The heat conductivity extrapolated in nonzero external field region.

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