After effect, magnetic

Not considered in this review are the removal of energetic equivalence by an applied field or stress where, as in a spinel, the energetically equivalent sites have differently oriented crystal-field axes. This lifting of site degeneracy coupled with charge transfer between mixed-valence states leads to such phenomena as magnetic after effect and photoinduced anisotropy ... 

Shelkovnikov et al. (1976), for (Sm, Gd)Cos-xCux films prepared by flash evaporation onto substrates heated to 470 K, have observed large magnetic after effects. They discuss the origin of such properties and show that these effects are characteristics of high coercivity in the materials. 

Num] Numakura, H., Mima, M., Matsumoto, H., Koiwa, M., Nitrogen Trapping to Chromium in a Iron Studied by Internal Friction and Magnetic After-Effect Techniques , ISIJ Int., 36(3), 290-299 (1996) (Crys. Structme, Experimental, Magn. Prop., 40)... 

Ferrer et al. (1978) invariably found serious deviations of the experimental magnetization curves from model predictions in the low-field region. The deviations originate from the presence of sizable hysteresis loops and magnetic after-effects. These effects were studied in more detail by Boucher and Barbara (1979) on the alloy Tb52Ag4g. They found that the coercive force depends on the temperature and the observation time according to the following relation ... 

Shifts of the aromatic carbon atom directly attached to the substituent have been correlated with substituent electronegativity after correcting for magnetic anisotropy effects shifts at the para aromatic carbon have been correlated with the Hammett a constant. Ortho shifts are not readily predictable and range over about 15 ppm. Meta shifts are generally small-up to several parts per million for a single substituent. 

Figure 40 Three-dimensional anisotropy of the magnetic field effect on photoconduction of a 7 um-thick tetracene single crystal illuminated through a semitransparent gold evaporated anode (cf. Fig. 39a). (a) Relative increase of the photocurrent (iph) when a magnetic field B = 0.5T is rotated perpendicular to the a 6-plane for different orientations of the crystal

The photolyses of 1,2-dipheny1-2-methyl-1-propa-none and its 2h and derivatives in micellar solution are now described and further demonstrate the enhanced cage and magnetic isotope effects of mlcelllzatlon. We report also the observation of CIDP during the photolyses of micellar solutions of several ketones, and demonstrate the validity of the radical pair model to these systems. Analyses of the CIDNP spectra in the presence and absence of aqueous free radical scavengers (e.g., Cu2+) allow us to differentiate between radical pairs which react exclusively within the micelle and those that are formed after diffusion into the bulk aqueous phase. In some cases this allows us to estimate a lifetime associated with the exit of free radicals from the micelles. 

The magnetic isotope effect on the lifetime of the observed transients as well as the amount of cage recombination has been studied by various authors38,41 43>. Experimentally, there are several species which can absorb light after laser excitation... 

Fig. 6-3. Magnetic field effects observed in the radiation reaction of a squalane (S) solution of fluorene (M) for pulse radiolysis with a 4-MeV electron accelerator. The reaction temperature is not described in the present papers, but may be room temperature, (a) Time profile of fluorine fluorescence during and after pulse radiolysis of a squalane solution (1) at the minimum field less than 0.05 mT, where the residual field of an electromagnet is cancelled by passing a small reverse current through the magnet s coils (2) at 0.3 T. (b) The time dependence of the magnetic field enhancement of the fluorescence intensity (A) 15-ns pulse ( ) 50-ns pulse, (c) The MFE on the increase in fluorescence intensity at 200 ns after the pulse. (Reproduced from Ref. [18b] by permission from The American Chemical Society)...

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