Coupling ferromagnetic

The muffin-tin potential around each atom in the unit cell has been calculated in the framework of the Local-Spin-Density-Approximation using the ASW method. The ASW method uses the atomic sphere approximation (ASA), i.e. for each atom a sphere radius is chosen such that the sum of the volumes of all the overlapping spheres equals the unit cell volume. The calculation yields the expected ferromagnetic coupling between Cr and Ni. From the self-consistent spin polarized DOS, partial and total magnetic moment per formula unit can be computed. The calculated total magnetic moment is 5.2 pg in agreement with the experimental value (5.3 0.1 e calculations presented here have been performed... 

We also mention the octanuclear chromic wheels [CrF(02CCMe3)2]8 (41) and [Cr8(0H)8(02CPh)i6] (42), which contain eight Cr(III) ions anti-ferromagnetically coupled. 

All Ni2 dinuclear complexes have Ni—N—Ni angles in the narrow range 101-105° and exhibit ferromagnetic coupling with /-values between + 27 cm 1 and I 73 cm 1. It should be noted though, that due to the zfs effects manifest at low temperatures the magnitude of J should be treated with care in the ferromagnetic case. 

As can be expected from the EO coordination mode of the azido ligand, all these complexes show ferromagnetic coupling. The field dependence of the magnetization in the low temperature region has been interpreted as indicative of metamagnetic behavior. 

Christou, Flendrickson, and co-workers reported triply bridged, ferromagnetically coupled dicopper(II) complexes (630) and (631).504-506 Perlepes et al. reported alkoxo-/carboxylato-bridged complexes (632) and (633).506 Using hydroxo-/carboxylato-bridged dicopper(II) complexes, Chakravarty and co-workers investigated magnetostructural correlations complexes (634) and (635)... 

Although extended ID systems comprising ferromagnetically coupled gadolinium and copper ions were obtained [46], the exchange interactions were too weak to provide significant effects and the increase of the x l product was observed only at very low temperatures. A much richer scenario was instead... 

Dy3+-Dy3+ ferromagnetic coupling has also been observed in a double chain based on the triangular motif (topologic mode (B) in Scheme 4.1) [74]. Slow relaxation is observed (A = 44.2K, r0 = 2.4 X 10-8 s) but its ID origin is not demonstrated, and the onset of 3D ordering is visible at low temperature. 

If we first consider the three scenarios at the same field, we can immediately see how the paramagnetic material shows the largest magnetocaloric effect, followed by a ferromagnetically coupled system, and then the antiferromagnetic case. 

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