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Phase Competition in the Palmer-Chalker XY Pyrochlore Er_{2}Pt_{2}O_{7}.

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We studied Er2Pt2O7, a frustrated pyrochlore magnet, using neutron scattering. It orders into a unique magnetic structure at a low temperature, driven by quantum fluctuations and competing magnetic states.

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Area of Science:

  • Condensed Matter Physics
  • Magnetism
  • Materials Science

Background:

  • Frustrated pyrochlore magnets exhibit complex magnetic ordering due to competing interactions.
  • Er2Ti2O7 and Er2Ge2O7 are known XY pyrochlore antiferromagnets with higher ordering temperatures.
  • Understanding magnetic structures and excitations is key to developing novel magnetic materials.

Purpose of the Study:

  • To investigate the magnetic properties of Er2Pt2O7, a new member of the XY pyrochlore family.
  • To determine the magnetic structure and excitations of Er2Pt2O7 using neutron scattering.
  • To understand the role of quantum fluctuations and competing phases in its magnetic behavior.

Main Methods:

  • Neutron scattering measurements (elastic and inelastic) were performed on Er2Pt2O7.
  • Symmetry analysis was used to determine the magnetic structure.
  • Magnetic heat capacity measurements were conducted.
  • Classical spin-wave calculations were employed for comparison.

Main Results:

  • Er2Pt2O7 orders into the k=0, Γ7 magnetic structure (Palmer-Chalker state) at T_N = 0.38 K.
  • This ordering temperature is significantly lower than its sister compounds Er2Ti2O7 and Er2Ge2O7.
  • A broad anomaly in magnetic heat capacity at T* = 1.5 K indicates strong short-range spin fluctuations.
  • Inelastic neutron scattering revealed a gapped spin-wave spectrum with a flat band and a diffusive band.
  • Discrepancies between experimental data and classical spin-wave predictions suggest enhanced quantum fluctuations.

Conclusions:

  • Er2Pt2O7 exhibits a unique magnetic ground state distinct from its sister pyrochlores.
  • Enhanced quantum fluctuations, arising from phase competition between Γ7 and Γ5 states, significantly suppress the ordering temperature.
  • The observed spin-wave spectrum provides evidence for the interplay between classical and quantum effects in this frustrated magnet.