Comparison of the spin exchange interactions in PbCu2(PO4)2 and SrCu2(PO4)2 on the basis of spin dimer analysis

Schematic representation of the spin lattice in PbCu2(PO4)2. The numbers 1, 2, 3, and 4 refer to the spin exchange paths J1, J2, J3 and J4, respectively.