Antisymmetric double exchange in trimeric mixed-valence clusters

Spin Switching in Molecular Quantum Cellular Automata Based on Mixed-Valence Tetrameric Units

“…First , there is a strong correlation between the molecular spin and the degree of localization in mixed valence clusters. Indeed, when the extra electrons are delocalized over the paramagnetic “spin cores”, the spin-dependent electron transfer (also known as “double exchange”) takes place. − ,,− ,, The spin-dependent electron transfer occurs also in systems in which the pair of electrons is delocalized over diamagnetic “spinless cores”. As an example, one can mention reduced mixed valence polyoxometalates, which exhibit either magnetic or nonmagnetic ground states depending on the relative strength of different one-electron hopping parameters − (see also ref and refs therein).…”

“…From this point of view the proposal , to realize such cells by mixed valence molecules seems to be especially promising because they naturally have two or more metal sites with different oxidation degrees forming thus specific charge configurations, while the vibronic coupling can lead to the self-trapping and consequently to the barrier between these localized configurations. This circumstance refers to the dinuclear and polynuclear mixed valence systems which were a subject of intensive study in molecular magnetism during several decades. − …”

Anisotropic double exchange in a valence-delocalized [Fe2.5+Fe2.5+] cluster. Spin–orbit coupling in the Anderson–Hasegawa double exchange model

“…For the MV systems, the account of the spin-orbit coupling for the transfer of hole between the neighboring sites in doped La 2 CuO 4 results in the spin-orbit hopping term and symmetric anisotropic exchange [48]. For the MV [d n -d n+1 ] dimers of orbitally non-degenerate ions, taking spin-orbit coupling into account in the Anderson-Hasegawa DE model (in the second-order perturbation theory) results in an antisymmetric DE interaction [49][50][51]. As shown in Ref.…”

Antisymmetric double exchange in mixed-valence clusters

“…D is proportional to the cluster AS DE parameter K Z ¼ ðK Z ab þ K Z bc þ K Z ca Þ=3: The microscopic consideration of the AS DE coupling in the MV trimer shows that the cluster AS DE vector is directed along the trimer trigonal Z-axis: G i with different S and also the spin-frustrated S states of the MV trimers with high individual spins. These mixings determine the second-order contributions of the AS DE and DM AS exchange of the form S½ðnK Z þ pD Z DM Þ 2 =ðqt þ rJÞ to the cluster ZFS parameters D S ð 2Sþ1 G i Þ of axial anisotropy, D Z DM ¼ ðD Z ab þ D Z bc þ D Z ca Þ=3; D Z DM BWJl=e j ; D Z DM 5K Z ; n; p; q; r are the numbers [9]. The second-order AS DE contributions to the axial ZFS parameters D S ð 2Sþ1 G i Þ; D S oK Z ; are different for the 2Sþ1 A 1 ; 2Sþ1 A 2 and 2Sþ1 E terms, H ZFS ¼ D S ð 2Sþ1 G i Þ½S 2 z À SðS þ 1Þ=3:…”

“…10 cm À1[9]. For the DE-frustrated states 2Smaxþ1 E with maximal S; the AS DE linear splitting is e ASDE ð 2Smaxþ1 E 7 ; MÞ ¼ E DE term determines the strong anisotropy of the Zeeman splittings, axial anisotropy of the g-factors ðg jj ¼ g 0 ; g > ¼ 0Þ and the magnetic moment.…”