Cobalt-containing calcium fluorohydroxyapatites with properties of field-induced single-ion magnets

Abstract

Partially substituted calcium fluorohydroxyapatite Ca10(PO4)6[(CoO2)xFy(OH)2−(2x+y)] samples were obtained by the solid state synthesis. The linear channels of the samples contain dioxocobaltate ions characterized under an external magnetic field by the slow relaxation of magnetization with the remagnetization energy barrier Ueff = 61–65 cm−1≈2|D|, which coincides with the barrier for similar apatite samples containing no fluorine. Fluoride ions exert no significant effect on the magnetic properties of the dioxocobaltate ions but substantially decrease the concentration of paramagnetic cobalt.