A new binary Co1/2Fe1/2(H2PO4)(2)center dot 2H(2)O was synthesized by a simple, rapid and cost-effective method using CoCO3-Fe(c)-H3PO4 system at ambient temperature. Thermal treatment of the obtained Co1/2Fe1/2(H2PO4)(2)center dot 2H(2)O at 600 degrees C yielded as a binary cobalt iron cyclotetraphosphate CoFeP4O12, The FTIR and XRD results of the synthesized Co1/2Fe1/2(H2PO4)(2)center dot 2H(2)O and its final decomposed product CoFeP4O12 indicate the monoclinic phases with space group P2(1)/n and C2/c, respectively. The particle morphologies of both binary metal compounds appear the flower-like microparticle shapes. Room temperature magnetization results show novel superparamagnetic behaviors of the Co1/2Fe1/2(H2PO4)(2)center dot 2H(2)O and its final decomposed product CoFeP4O12, having no hysteresis loops in the range of +/-10,000 Oe with the specific magnetization values of 0.045 and 12.502 emu/g at 10 kOe, respectively. The dominant physical properties of the obtained binary metal compounds (Co1/2Fe1/2(H2PO4)(2)center dot 2H(2)O and CoFeP4O12) are compared with the single compounds (M(H2PO4)(2)center dot 2H(2)O and M2P4O12; where M = Co, Fe), indicating the presence of Co ions in substitution position of Fe ions. (C) 2009 Elsevier Ltd. All Fights reserved.