Magnetism in Binuclear Compounds: Theoretical Insights

The resolution of the weak-exchange limit made rigorous, simple and general in binuclear complexes

“…In the absence local orbital momentum, the model multispin Hamiltonian expression reads: 33,36,69 where a and b label the two magnetic centers, Ŝ a and Ŝ b are spin operators, J is the Heisenberg exchange magnetic coupling, are rank-2 tensors describing the local anisotropies, is a rank-2 tensor describing the symmetric anisotropic exchange, and d̄ is a pseudovector describing the antisymmetric component of the anisotropic exchange. In centrosymmetric complexes, the latter term of eqn (1), also referred to as the Dzyaloshinskii–Moriya interaction (DMI), 70–75 vanishes, and otherwise, may be less important than the other terms unless specific situations are encountered (exotic coordination environment and/or orbital near-degeneracy).…”

“…[40][41][42][43][44][45][46][47] It is worth noting that density functional theory (DFT) is equally involved in rationalizing magnetic data, [48][49][50][51][52][53][54] as well as single-reference spin-flip approaches, [55][56][57] and more recently coupled-cluster methods. [58][59][60] In principle, the low-energy ab initio spectrum offers sufficient detail for calculating anisotropy parameters and spin-orbit correction to the exchange interaction if a SOCI is performed, 22,33 as well as EPR parameters and wT profiles provided that the Zeeman interaction is treated. 46,[61][62][63][64] This is the starting point of our work.…”

“…With both model Hamiltonians, the theoretical extraction of relevant parameters is based on an explicit mapping onto an effective Hamiltonian (H ˆeff ) that is built on top of the ab initio calculations. [29][30][31][32][33] Alternatively, one may skip the explicit projection of the wave functions and work within the pseudospin framework. 34 Since H ˆGS targets only the ground spin state it is quite clear that it is not fully relevant in the weak-exchange limit.…”