| Abstract: | Structural and Magnetochemical Studies at the Ternary Phosphates Ba2MII(PO4)2 (MII = Mn, Co) and Refinement of the Crystal Structure of BaNi2(PO4)2 Single crystals of the following phosphates were grown by the floating zone technique using a mirror furnace and their crystal structures refined (0,02 < R1 < 0,04 and 0,04 < wR2 < 0,10, resp.): Ba2Mn(PO4)2 (a = 531.1(1), b = 896.8(1), c = 1625.6(3) pm, β = 90.26(1)°), Ba2Co(PO4)2 (a = 529.8(1), b = 884.4(1), c = 1614.4(3) pm, β = 90.68(2)°) and BaNi2(PO4)2 (a = 480.0(1), c = 2327.3(5) pm, Z = 3, space group R3). Both compounds Ba2MII(PO4)2 crystallize with Z = 4 in space group P21/n of the monoclinic Ba2Ni(PO4)2 type; BaNi2(PO4)2 has the hexagonal‐rhombohedral structure of the BaNi2(AsO4)2 type. Magnetic measurements of powders of Ba2Mn(PO4)2 and Ba2Co(PO4)2 yielded room temperature moments of μeff = 5,73 and 4,93 μB, resp., but only the manganese compound obeys the Curie‐Weiss law down to low temperatures. Weak antiferromagnetic interactions at both compounds only near TM ≈ 5 K lead to a reciprocal susceptibility minimum. |
