RAGHUNATHAN, Rajamani; SUTTER, Jean-Pascal; DUCASSE, Laurent; DESPLANCHES, Cédric; RAMASESHA, S.

doi:10.1103/PhysRevB.73.104438

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RAGHUNATHAN, Rajamani
Solid State and Structural Chemistry

SUTTER, Jean-Pascal
Institut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
Laboratoire de chimie de coordination [LCC]

DUCASSE, Laurent
Laboratoire de Physico-Chimie Moléculaire [LPCM]

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Physical Review B: Condensed Matter and Materials Physics (1998-2015). 2006, vol. 73, n° 10, p. 104438 (8 p.)

American Physical Society

Résumé en anglais

Conventional superexchange rules predict ferromagnetic exchange interaction between Ni(II) and M (M=Mo(V), W(V), Nb(IV)). Recent experiments show that in some systems this superexchange is antiferromagnetic. To understand this feature, in this paper we develop a microscopic model for Ni(II)-M systems and solve it exactly using a valence bond approach. We identify the direct exchange coupling, the splitting of the magnetic orbitals and the inter-orbital electron repulsions, on the M site as the parameters which control the ground state spin of various clusters of the Ni(II)-M system. We present quantum phase diagrams which delineate the high-spin and low-spin ground states in the parameter space. We fit the spin gap to a spin Hamiltonian and extract the effective exchange constant within the experimentally observed range, for reasonable parameter values. We also find a region in the parameter space where an intermediate spin state is the ground state. These results indicate that the spin spectrum of the microscopic model cannot be reproduced by a simple Heisenberg exchange Hamiltonian.< Réduire

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Molecular magnets

Strongly correlated electron systems

Heavy fermions

Exchange and superexchange interactions

Numerical simulation studies

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Microscopic Model for High-spin vs. Low-spin ground state in [Ni2M(CN)8](M=MoV, WV, NbIV) magnetic clusters

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