Hyperfine-field anisotropy

The results of these modeling studies are shown in Figures 2 and 3> The value of ic (anisotropy constant) was chosen so that the average particle radius determined from the reduction in the average hyperfine field splitting due to collective magnetic excitations... 

Figure 11. The best fit has been found for 5 = 0.7 0.01 nuns, Aitg =—3.25 0.01 nuns, " =(2.11, 2.19, 2.00), "T/ nMn = (-45, 10, 19) T, tj = 0.74 0.1, D = 7.2 0.5 cm, and EID = 0.16 0.02. The zero-field splitting parameter D = 7.2 0.5 cm is comparable to that found for rabredoxin from Clostridium pasteurianum (D = 7.6cm Surprisingly, the rhombicity parameter E/D = 0.16 0.02 differs somewhat from that of rubre-doxin from C. pasteurianum (E/D = 0.28). The hyperfine coupling tensor has been determined to be A = (-14.5, -9.2, -27.5) T. The anisotropy of the hyperfine conpling tensor is cansed by spin-orbit confribntions to the internal magnetic hyperfine field.

For FeF2 it was found that D = 1-36 0-03, (f = 0-325 0-005, and the hyperfine field at the absolute zero Hq — 329 2 kG. This behaviour is remarkably similar to that of MnF2 despite the appreciably lower anisotropy in this latter compound. 

E/Z) = 0.16 0.02 differs somewhat from that of rubredoxin from C. pasteurianum ElD = 0.28). The hyperfine coupling tensor has been determined to be A = (—14.5, —9.2, —27.5)T. The anisotropy of the hyperfine coupling tensor is caused by spin-orbit contributions to the internal magnetic hyperfine field. 

Fig. 2. Qualitative variation of the nuclear magnetic resonance frequency with the strength of an applied external field for a spherical ferromagnetic sample with negligible magnetic anisotropy and isotropic, positive hyperfine field at low temperature (saturated magnetization).

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