Ferromagnetic-ferrimagnetic coupling

Annelated macrocyclic polyradicals consist of calix[4]arene-based macrocycles annelated via bis(3,4 -biphenylene)methyl linkers. This connectivity is consistent with the ferromagnetic-ferrimagnetic coupling scheme, for which scaling of S with the number of radical sites (or molecular weights) was attained.8,112... 

SQUID magnetic studies of 57 in THF-d8 matrix revealed a relatively high average value of S 18. Values of Msat 0.4-0.6 pB indicate 40-60% of unpaired electrons in the limit of very low temperature and high field for both polyradicals, which is consistent with the ferromagnetic-ferrimagnetic coupling scheme.8,113 These results may be compared with the value of Sx 40-50 expected for defect-free... 

Values of Msat 0.5 fiB, indicating presence of approximately 50% of unpaired electrons at low temperature, did not show any systematic dependence on degree of polymerization of polyether. Overall, this results were consistent with the ferromagnetic-ferrimagnetic coupling scheme and presence of chemical defects.8... 

Fig. 38 Polymers 57 and 58 with the ferromagnetic-ferrimagnetic coupling scheme with the macrocyclic (S — 3 and 5 = 2) and cross-linking (5=1 /2) modules.

Cr3Te4 is ferromagnetic below Of = 329° K (186), but below 80° K an antiferromagnetic component seems to be superimposed. The ferrimagnetism found in Fe3Se4 (187) also does not simply result from an antiparallel coupling of (001) layers. 

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