Induced-moment spin glass

From the experimental definition of a unique anisotropy field by these measurements and from the result of an NMR analysis (Alloul 1979a, b) that almost all local moments are involved in the magnetization rotation, Alloul and Hippert (1983) conclude that for T small applied fields induce a macroscopic rotation of the spins in their metastable configuration. Further evidences for a macroscopic anisotropy in spin glasses are also found by ESR experiments (Monod and Berthier 1980) and measurements of the magnetic hysteresis (Monod et al. 1979). 

The compound PrP exists off-stoichiometry, as found by Franceschi and Olcese (1968), with the NaCl structure. Phosphor-deficient samples show an induced magnetic moment on the Pr sites (Hasanain et al. 1981). Spin-glass behaviour (Westerholt and Methfessel 1977) seems to occur in such compounds. 

Since the transition moment of the spin-forbidden T,- Sq transition is very small, the natural lifetime rj of the triplet state is long. Consequently, radiationless processes can compete with phosphorescence in deactivating the T state. Of particular importance are collision-induced bimolecular processes (cf. Section 5.4), and phosphorescence of gases and liquid solutions is relatively difficult to observe (Sandros and Backstrom, 1962). An exception is biacetyl with a very short T, lifetime rj. (Cf. Figure 5.3.) Phosphorescence spectra are commonly measured using samples in solvents or mixed solvents that form rigid glasses at 77 K (such as EPA = ether-pentane-alcohol mixture). (Cf., however. Example 5.6). 

---