ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
The magnetic contribution to the specific heat Cm(T) of polycrystalline Ising-like spin glasses (SG) ScEr(1.05; 2.5 at. % Er) and ZnMn (195, 270 ppm Mn) has been measured in the temperature range 0.1〈T〈2.5 K, using a nonadiabatic heat pulse method. Cm(T) of the x-y–like SG CdMn (488 ppm Mn) has been measured on single crystals in external fields (Bex≤6 T) with Bex either ⊥ or (parallel) to the c axis. The data are compared with susceptibility measurements.1 For all samples the behavior of Cm(T) is similar to that in archetypal SG's. There is scaling and a linear dependence Cm(T) for T→0. The high-temperature data do not follow a simple 1/T or 1/T2 law. In contrast to the results from mean-field calculations for uniaxial systems we find no peaks in Cm(T). Yet, the relatively sharp maxima in Cm(T) at Tm of ScEr and ZnMn are close to the freezing temperatures T(parallel)g. In CdMn T⊥g from χ(T) lies well below Tm. The data for ScEr and ZnMn can be fitted within a two-level system model. For CdMn Cm is stronglydependent on Bex and shows anisotropic behavior. For Bex⊥ c (parallel to the easy axis) Cm(T,B) is SG-like for all fields and comparable to isotropic SG's. With increasing fields Tm shifts to higher temperatures and the slope in the linear range decreases. For Bex(parallel)c (hard direction) the behavior is quite different. For Bex 〈2 T the linear slope in Cm(T) and Tm are only weakly dependent on Bex. Increasing the field leads to a remarkable reduction of Cm(T) around Tm, and Cm(T) becomes nonlinear for T→0. This can be understood in terms of new mean-field calculations on anisotropic Ising-SG's by Usadel,2 who predicts a breakdown of the SG interactions in strong magnetic fields transverse to the easy axis.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.338542
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