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Magnetic field-tuned magnetic order and metamagnetic criticality in non-stoichiometric CeAuBi$_2$

H. Hodovanets, H. Kim, T. Metz, Y. Nakajima, C. J. Eckberg, K. Wang, J. Yong, S. R. Saha, J. Higgins, D. Graf, N. Butch, T. Vojta, J. Paglione

Abstract

We present a detailed study of magnetization, resistivity, heat capacity, and X-ray and neutron powder diffraction measurements performed on single crystals of non-stoichiometric CeAuBi$_2$, Au deficiency 18$\%$, a strongly correlated antiferromagnet with Néel temperature T$_N$ = 13.2 K. Field-dependent magnetization measurements reveal a large magnetic anisotropy at low temperatures with an easy axis along the crystallographic c-axis, in which direction a spin-flop transition exhibits strong features in magnetization, specific heat, and resistivity at H$_c$ = 75 kOe. The constructed temperature-field phase diagram connects this transition to the suppression of magnetic order, which evolves from a second-order nature into a first-order transition that bifurcates at the spin-flop into three transitions below 1 K. The smoothed nature of the metamagnetic transitions in non-stoichiometric CeAuBi$_2$ is well described by an Ising model with weak quenched disorder, suggesting that the presence of Au vacancies is sufficient to smear the complex metamagnetic behavior and tune the critical behavior of magnetic order.

Magnetic field-tuned magnetic order and metamagnetic criticality in non-stoichiometric CeAuBi$_2$

Abstract

We present a detailed study of magnetization, resistivity, heat capacity, and X-ray and neutron powder diffraction measurements performed on single crystals of non-stoichiometric CeAuBi, Au deficiency 18, a strongly correlated antiferromagnet with Néel temperature T = 13.2 K. Field-dependent magnetization measurements reveal a large magnetic anisotropy at low temperatures with an easy axis along the crystallographic c-axis, in which direction a spin-flop transition exhibits strong features in magnetization, specific heat, and resistivity at H = 75 kOe. The constructed temperature-field phase diagram connects this transition to the suppression of magnetic order, which evolves from a second-order nature into a first-order transition that bifurcates at the spin-flop into three transitions below 1 K. The smoothed nature of the metamagnetic transitions in non-stoichiometric CeAuBi is well described by an Ising model with weak quenched disorder, suggesting that the presence of Au vacancies is sufficient to smear the complex metamagnetic behavior and tune the critical behavior of magnetic order.

Paper Structure

This paper contains 10 sections, 2 equations, 14 figures, 1 table.

Table of Contents

  1. Introduction
  2. Experimental details
  3. Results
  4. X-ray diffraction
  5. Neutron diffraction
  6. Basic physical properties
  7. Measurements with H$\|$c
  8. Discussion
  9. Conclusion
  10. Acknowledgment

Figures (14)

  • Figure 1: Powder X-ray diffraction patterns of ground CeAuBi$_2$ single crystals. Broad peaks at around 2$\Theta$ = 20 degrees are due to Kapton tape and acrylic glass (airtight container). The inset: X-ray diffraction pattern of single crystal of CeAuBi$_2$. The few low-intensity peaks marked with dots can be associated with Bi flux.
  • Figure 2: (a) Powder neutron diffraction patterns of ground CeAuBi$_2$ single crystals at 20 and 4 K. The pattern in blue shows the difference between the two patterns, i.e. the magnetic contribution. (b) Powder neutron diffraction pattern at 4 K with Rietveld fit (black curve) and the difference between them (blue curve). (c) Schematic representation of the magnetic structure (solid lines) of CeAuBi$_2$. The magnetic unit cell is twice the crystallographic unit cell (represented by a dashed line) along the $c$-direction. (d) Magnetic moment refined from the neutron diffraction data as a function of temperature.
  • Figure 3: (a) Temperature-dependent susceptibility of CeAuBi$_2$ single crystal for H$\|\textbf{a}$, H$\|\textbf{c}$ and polycrystalline average $\chi_{ave}$=(2$\chi_a$+$\chi_c$)/3. The arrow denotes the AFM transition. (b) Field-dependent magnetization of CeAuBi$_2$ single crystal at 1.8 K for H$\|\textbf{a}$ and H$\|\textbf{c}$. (c) Temperature-dependent resistivity of CeAuBi$_2$ single crystal. (d) Temperature-depended specific heat of CeAuBi$_2$. The inset shows $C_p/T$ vs $T^2$ data.
  • Figure 4: Temperature-dependent susceptibility of CeAuBi$_2$ single crystal for H$\|\textbf{c}$. Inset, d($M$/$H$)/d$T$ of CeAuBi$_2$, H$\|\textbf{c}$.
  • Figure 5: (a) and (b) Field-dependent magnetization of CeAuBi$_2$ single crystal for H$\|\textbf{c}$. The curve for $T$ = 6.6 K is shown on both panels for continuity. (c) and (d) the derivative d($M$)/d$H$ of the data presented in panels (a) and (b), respectively.
  • ...and 9 more figures