Abstract
Re-entrant spin glass (RSG) transitions in Ni-Mn and Au-Fe have been reassessed by acoustic measurements of the magneto-mechanical damping by domain walls. Stress-induced non-thermally activated domain wall dynamics is progressively replaced by an intense thermally activated relaxational response when the temperature approaches the RSG freezing point. A “frozen” state with negligible motion of domain walls on atomic and mesoscopic scales occurs in the RSG. We propose that RSG freezing has its origin in intrinsic properties of domain walls.
Highlights
Re-entrant spin glass (RSG) transitions in Ni-Mn and Au-Fe have been reassessed by acoustic measurements of the magneto-mechanical damping by domain walls
The wide scope of possible candidates for “pinners” during RSG freezing exemplifies the difficulties in identifying their possible origin
To clarify the involvement of domains walls in RSGs, we conducted new acoustic experiments studying the magneto-mechanical damping (MMD), which will be expressed as logarithmic decrement of oscillations δ
Summary
Re-entrant spin glass (RSG) transitions in Ni-Mn and Au-Fe have been reassessed by acoustic measurements of the magneto-mechanical damping by domain walls. The co-existence of ferromagnetism and glass-like states may relate to atomic scale chemical disorder Another line of thinking, not invoking atomic-scale structural disorder, considers the role of magnetic domain walls in RSG materials, which were observed above and below Tf14,15. Not invoking atomic-scale structural disorder, considers the role of magnetic domain walls in RSG materials, which were observed above and below Tf14,15 This model involves a strong decrease of the domain wall mobility[15] and explains the near vanishing of χ′. In addition to uncertainties about the pinning mechanism, the domain wall pinning concept does not explain the existence of “frustrated spins” in disordered RSGs. a similar line of thought, recently introduced in analogy with ferroelectrics[21,22], involves a generic concept of “domain glasses”. A linear micro eddy current damping, δμ, measured at low strain amplitudes, a linear macro eddy current damping component, δM, and a non-linear hysteretic damping, δh(ε0), emerging at higher strain amplitudes
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