Doping-induced spin-manipulation in complex trimer system Ca3Cu3(PO4)4: A density functional investigation

• The present work is a density-functional-based detailed investigation of the effects of spin-manipulated doping of Ca3Cu3(PO4)4.
• Site-selective doping with Mg is more efficient than Ni in obtaining a spin-gap system with singlet ground state.
• Doping induced dimerized state is found to be the lowest in ground-state energy.
• We suggest a model spin-Hamiltonian from which the relevant exchange integrals can be calculated.
• Calculated spin exchange values along various possible paths resemble nicely with experimental results.

Doping induced spin-manipulation with magnetic (Ni) and non-magnetic (Mg) dopants constitutes the experimental attempts to obtain a singlet ground state system from the linear chain Heisenberg antiferromagnetic Cu-based d9 spin-1/2 trimer compound Ca3Cu3(PO4)4 with doublet ground state. The present study is a density-functional investigation of the effects of such doping on the spin-exchange mechanism and electronic structure of the parent compound. Site-selective doping with zero-spin dopants like Mg is proved to be more efficient than an integral spin dopant Ni in obtaining a spin-gap system with singlet ground state, as also observed in the experimental studies. Doping induced dimerized state is found to be the lowest in ground-state energy. Calculated spin exchange couplings along various possible pathways are observed to attain good agreement with earlier experimental results with suitable optimization of Coulomb repulsion (U) and exchange (J) parameters.