Determination of the critical exponents in the Ag Mn spin glassReport as inadecuate

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Abstract : We present nonlinear magnetization measurements in the AgMn spin glass in a wide concentration range 0.4 % < c < 24 %. The analysis of the results in the frame work of the existence of a phase transition at Tg yields the critical exponents δ = 3.1 ± 0.2, γ = 2.2 ± 0.2, and β = 1 ± 0.1. These exponents are obtained from three independent experimental determinations in the range of temperature and magnetic field in which T - Tg- Tg < 0.1 and the nonlinear magnetization is less than 10 % of the total magnetization. Outside this range, deviations towards higher apparent values of the critical exponents are systematically observed which explains the disagreement between our findings and those on the CuMn system 5. The analysis of the mean-field Sherrington-Kirkpatrick equations 17 indeed shows that the presence of regular terms alters the determination of the critical exponents for T - Tg-Tg > 0.1 and H > 0.1. This point of view may also help to clarify the diversity existing between the values of the critical exponents determined in other systems.

Mots-clés : magnetic transitions magnetisation manganese alloys silver alloys spin glasses

Author: H. Bouchiat



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