Intercalation of Cu2+ in the HNiPO4 center dot H2O layered phosphate: Study of the structure, spectroscopic, and magnetic properties of the intercalated derivative and the related CuNi2(PO4)(2) compound

A Cu(II) intercalated phase was obtained from the insertion of Cu(II). ions in the HNiPO4-H2O layered phosphate, This phase was characterized by using XRD, analytical, and spectroscopic techniques. The intercalation process d oes not introduce any significant change in the structure of the nickel pho sphate layers. However,the distance between layers shows an increase induce d by the homogeneous distribution of the Cu(II) ions in the interlayer spac e. The CuNi2(PO4)(2) heterometallic phosphate was obtained from the thermal treatment of the Cu(II) intercalated compound. CuNi2(PO4)(2) crystallizes in the monoclinic P2(1)/n space group, with cell parameters a = 6.393(1), b = 9.325(1), and c = 4.718(1) jj; beta 90.71(1)degrees; V = 281.24 Angstrom (3); and Z = 2, The three-dimensional structure is built by corner-sharing PO4 tetrahedra, CuO4 planar squares, and Ni2O3 dimers. The Ni(II) ions exhi bit, in this compound, an unusual five-coordination with a geometry interme diate between trigonal bipyramid and square-planar pyramid but slightly clo ser to the latter disposition. ESR and magnetic measurements for the interc alated derivative and the CuNi2(PO4)(2) compound suggest the presence of ma gnetic couplings of long-range order between the Cu(II) and Ni(II) ions in both cases. Thelayered intercalated derivative shows an antiferromagnetic t hree-dimensional behavior in which the interlayer magnetic interactions are established;through the inserted Cu(II) ions. In the ease of the CuNi2(PO4 )(2) phase, a global antiferromagnetic ordering is observed with a transito ry ferrimagnetic behavior in the 75-40 K temperature range due to the spin decompensation of the coupled Cu(II) and Ni(II) ions present in the structu re.