Spin-freezing temperature

Coey and von Molnar (1978), by rf sputtering deposition, have studied a DyCu alloy with the following composition DyCU1.44Ar0.05O0.23- They observed a sharply defined spin-freezing temperature at 18K marked by a cusp in the low-field dc susceptibility (as for the Gd-Al system). They developed and discussed a... 

In the paramagnetic regime (T > Tm), the spectra in a weak LF (needed to suppress the depolarization by Cu nuclear dipoles) for x > 0.08 were most easily fitted to a power exponential (exp[—(At) ]) relaxation. Hence the summary label relaxation rate in fig. 113 (left) refers to the static width Aeff (see eq. 74) for T dynamic rate A for r > Tu- The variation of power p was studied in some detail for the 10% sample. A decrease fromp w 1 at high temperatures top w 0.6 close to Tm was found. This is another indication that a disordered spin-glass-like state is approached and 7m might best be considered a spin freezing temperature. This spin-glass-like state, however,... 

Fig. 24. Longitudinal field spectra for a Gaussian (left) and a Lorentzian (right) field distribution. The Gaussian case refers to spin freezing around 8.5 K in CePtSn, a concentrated spin system (Kalvius et al. 1995a) the Lorentzian case to a dilute Cu(Mn) spin glass below its glass transition temperature of 10.8K. The values of the longitudinal fields are (from top to bottom) 640, 320, 160, 80, 40 and OG (Uemuia et al. 1981). In both cases the set of spectra unambiguously proves that the spin systems are static.

Fig. 99. An example of inhamogeneous spin freezing, The sample is CeCuj Sij. (a) ZF xSR spectra, each consisting of a fast (static) and a slow (dynamic) relaxing signal. This distinction vanishes above 1K. (b) Relaxation rates vs. temperature, (c) Relative fractions of the spin-frozen (triangles) and the unfrozen (circles) parts. Tc is the superconducting transition temperature (see sect. 9.3.1.8) from Luke et al. (1994a).

Fig. 102. Left Temperature dependence of the near ZF muon spin relaxation rate in i-Tb Mg,2Zn5(i on double logarithmic scales. The vertical dashed line indicates the onset of loss of asymmetry due to instnunental dead time. The inset shows the temperature dependence of power used in the power exponential fit to the relaxation spectra. The spin-glass temperature is near 8K. Right pSR asymmetry spectra of i-Gd Mg42Zn5o at 1.5 K, in the applied longitudinal fields shown. The solid lines are a least-squares fit of a mildly inhomogeneous freezing...

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