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¹H NMR: Interpreting Distorted and Overlapping Signals01:02

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Spin systems where the difference in chemical shifts of the coupled nuclei is greater than ten times J are called first-order spin systems. These nuclei are weakly coupled, and their chemical shifts and coupling constant can generally be estimated from the well-separated signals in the spectrum.
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Sputter Growth and Characterization of Metamagnetic B2-ordered FeRh Epilayers
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From second to first order transitions in a disordered quantum magnet

Cugliandolo1, Grempel, da Silva Santos CA

  • 1Laboratoire de Physique Theorique de l'Ecole Normale Superieure, 24 rue Lhomond, 75231 Paris Cedex 05, France.

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|September 8, 2000
PubMed
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Quantum fluctuations can alter spin-glass transitions from second to first order, leading to discontinuous susceptibility and hysteresis. This disordered quantum model

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Area of Science:

  • Condensed matter physics
  • Quantum magnetism

Background:

  • Disordered quantum models exhibit complex phase transitions.
  • Classical spin-glass transitions are typically second order.

Purpose of the Study:

  • Investigate the impact of quantum fluctuations on spin-glass transitions.
  • Characterize the nature of phase transitions in a disordered quantum system.
  • Compare theoretical findings with experimental observations.

Main Methods:

  • Analysis of a disordered quantum spin-glass model.
  • Phase diagram exploration.
  • Investigation of critical phenomena and phase transition orders.

Main Results:

  • Identified regions where quantum effects are negligible, resulting in second-order transitions.
  • Discovered a region where quantum fluctuations drive first-order transitions.
  • Observed discontinuous susceptibility and hysteresis across the first-order line.
  • Qualitatively reproduced experimental data for LiHoxY1-xF4.

Conclusions:

  • Quantum fluctuations play a crucial role in determining the order of spin-glass transitions.
  • The model provides a framework for understanding experimental observations in materials like LiHoxY1-xF4.
  • Marginally stable spin-glass states and their relation to real-time dynamics were discussed.