Ferrimagnetic order

Figure 3.29 Ordered arrays of magnetic dipoles, represented by arrows (a) ferromagnetic ordering, (b) antiferromagnetic ordering, and (c) ferrimagnetic ordering.

Fe(isoquinoline)2(NCS)4] forms charge-transfer salts with tetrathiafulvalene and with bis(ethylenedithio)tetrathiafulvalene(51)." " The latter shows long-range ferrimagnetic ordering." " ... 

In the above examples, a transition-metal atom is invariably present. As such, one might believe that the unpaired d electrons of the transition metal are the main cause of ferro/ferrimagnetic ordering, the organic/molecular species only playing a secondary role. There are a few examples of molecular magnets without the transition-metal atoms, albeit showing low T s. These are p-nitrophenyl nitronyl nitroxide (T = 0.6 K)... 

Sf ferro- or ferrimagnetic ordering temperature (Curie point)... 

Use of antiferromagnetic coupled radical centers with a different number of spins per site, which can cancel only partially, leaving a magnetic moment (ferrimagnetic ordering) [377, 378]. 

The application of Mossbauer studies to magnetic materials is well illustrated by the spectra of magnetite (Fe304) shown in Fig. 2.48. Although this ferrimagnetically ordered material is an inverse spinel with nominally tetrahedral Fe + and both Fe and Fe on octahedral sites, at temperatures above 119 K (the Verwey transition temperature) only... 

F and FI stand for ferro- and ferrimagnetic ordering, respectively. The first compound on this list is not cubic. 

The solid solution Sr2(FeMOjjWi JOs also has the perovskite structure and the end-member Sr2Fe +Mo +Og is ferrimagnetically ordered at room temperature with a field of 315 kG [119]. Appreciable Fe " " content is not found until above 70% Sr2Fe +W 06 in composition because of appreciable reduction to W. ... 

Taylor and Christopher (1969) investigated for the first time the Co h)q)erfine fields in ferrimagnetically ordered GdCo2 and related compounds. They analysed the Co hyperfine field as a superposition of a contribution of the Co ion s own moment and the Co- and R-neighbour contributions,... 

Figure 19.3 Schematic of a partial unit cell and ferrimagnetic ordering of spinel ferrite structure.

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