Orthorhombic and triclinic modifications of the arsenate Cu₄O(AsO₄)₂ and isotypic phosphates Cu₄O(PO₄)₂: strongly frustrated antiferromagnetics

A structural-magnetic models of the orthorhombic and triclinic modifications arsenates Cu4O(AsO4)2 isotypic phosphates Cu4O(PO4)2 has been built analyzed. Their base elements are complicated ribbons composed antiferromagnetic Cu4 tetrahedra. Structurally, these tetrahedra have no shared copper atoms; however, there strong (AFM) ferromagnetic (FM) couplings between them, both within them. It established that strongly frustrated 3-D antiferromagnetics due to competition nearest AFM interactions along edges a multiplicity long-range secondary FM interactions. Additionally, large number weaker competing among each other. However, is possibility ordering Dzyaloshinskii-Moriya (DM) interaction in centrosymmetric modification (Pnma), because two three types magnetic ions, Cu1 Cu3, partial position 4c, where ions not related by inversion center. In (P -1) Cu4O(As(P)O4)2, all four equivalent 2i, which prevents DM This centrosymmetry will allow Cu4O(As(P)O4)2 be still at lower temperature. possible compounds quantum spin liquid.