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Pressure tuning of collapse of helimagnetic structure in Au2Mn

I-Lin Liu, Maria J. Pascale, Juscelino B. Leao, Craig M. Brown, William D. Ratcliff, Qingzhen Huang, and Nicholas P. Butch
Phys. Rev. B 96, 184429 – Published 27 November 2017
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  • INTRODUCTION
  • EXPERIMENTAL METHODS
  • RESULTS AND DISCUSSION
  • CONCLUSION
  • ACKNOWLEDGMENTS
    • References

    Abstract

    We identify the phase boundary between spiral spin and ferromagnetic phases in Au2Mn at a critical pressure of 16.4 kbar, as determined by neutron diffraction, magnetization, and magnetoresistance measurements. The temperature-dependent critical field at a given pressure is accompanied by a peak in magnetoresistance and a step in magnetization. The critical field decreases with increasing temperature and pressure. The critical pressure separating the spiral phase and ferromagnetism coincides with the disappearance of the magnetoresistance peak, where the critical field goes to zero. The notable absence of an anomalous Hall effect in the the ferromagnetic phase is attributable to the high conductivity of this material.

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    • Received 5 September 2017

    DOI:https://doi.org/10.1103/PhysRevB.96.184429

    ©2017 American Physical Society

    Physics Subject Headings (PhySH)

    1. Research Areas
    MagnetismMagnetotransport
    1. Techniques
    Pressure effectsPressure techniques
    Condensed Matter, Materials & Applied Physics

    Authors & Affiliations

    I-Lin Liu1,2,3,*, Maria J. Pascale2, Juscelino B. Leao1, Craig M. Brown1, William D. Ratcliff1, Qingzhen Huang1, and Nicholas P. Butch1,2

    • 1NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
    • 2Center for Nanophysics and Advanced Materials, Department of Physics, University of Maryland, College Park, Maryland 20742, USA
    • 3Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742-2115, USA

    • *ilin610@umd.edu

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    Issue

    Vol. 96, Iss. 18 — 1 November 2017

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    Images

    • Figure 1
      Figure 1

      (a) The scattering vector of magnetic 000+ peak moves from 0.18Å−1 to 0.15Å−1 and the spin angle shrinks to 38∘ when pressure rises to 10 kbar. The inset shows the tetragonal lattice structure and the corresponding spiral spin magnetic structure, which the in-plane spin locates at Mn atoms. (b) A comparison of the temperature dependence of spin angle determined from the (0,0,0)+ peak at ambient pressure (red dot) and 10 kbar (blue square). The gray line follows data from Ref. [10]. The uncertainties are smaller than the marker size.

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    • Figure 2
      Figure 2

      (a) Magnetization and (c) the first derivative of magnetization of Au2Mn up to 14 T. The inset highlights the distorted spiral transition zone between 0.2 T and 2.6 T. The hysteresis loop becomes narrow as temperature increases. (b) The MR ratio of Au2Mn at ambient pressure. Below 50 K, the peak at around 1.8 T indicates the SS-FM phase transition. This critical field of the SS-FM transition in Au2Mn decreases as temperature increases. (d) The temperature dependence of the critical field obtained from magnetization (red line) and MR (blue square) at ambient pressure. The agreement below 150 K suggests that the MR is a good probe of the low-temperature SS-FM phase boundary under pressure.

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    • Figure 3
      Figure 3

      Temperature dependence of MR ratio in Au2Mn under (a) 13.2 kbar and (b) 20.5 kbar (at room temperature). (c) Pressure dependence of MR of Au2Mn at 2 K. The black dotted line is the critical field defined by the field-induced peak in the MR, which indicates the SS-FM phase transition as a function of pressure and field. The red region has relatively large positive MR near the magnetic transition at 1.8 T at ambient pressure, and the positive MR peak at low field is gradually suppressed by a critical pressure of 16.4 kbar. (d) Hall resistance of Au2Mn at 2 K. The critical field decreases with pressure and is suppressed above the 16.4-kbar critical pressure.

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    • Figure 4
      Figure 4

      P−T phase diagram of Au2Mn showing the SS-FM phase boundary (red dots) determined through MR measurements, Neel temperature, and Curie temperatures (blue line) [19]. The almost vertical SS-FM phase boundary is demarcated by a dashed line.

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