Magnetic properties of some Cu-containing phosphates

Magnetic susceptibility and specific heat measurements are presented for some Cu-containing phosphates with different copper frameworks, M₂Cu(PO₄)₂ (M=Sr and Ba: linear 1D uniform chains), BaCuP₂O₇ (double 1D uniform chains), MCuP₂O₇ (M=Ca, Sr, and Pb: zig-zag 1D uniform chains), and Sr_9.1Cu_1.4(PO₄)₇ (isolated Cu²⁺ ions). We observed short- and long-range magnetic ordering in these compounds in which the main Cu-Cu interactions are transferred through PO₄ groups. In M₂Cu(PO₄)₂ and BaCuP₂O₇, J/k_B values of about 100-140 K and k_BT_N/J<1% were obtained.