Ferromagnetism in talc-like cobalt-phyllosilicates

The synthetic layered 1:1 phyllosilicate, Co2.3Al0.7Si1.3Al0.7O5(OH)(4), an d 2:1 phyllosilicates Co3Si4O10(OH)(0.7)F-1.3, Co3Si4O10(OH)(1.2)F-0.8(Co(C H3COO)(2))(0.24), Co3Si4O10(OH)(1.3)F-0.7 (TAEAH)(0.12) and Co3Si4O10(OH)(1 .3)F-0.7 (TAEAH)(0.24) have been obtained under hydrothermal conditions at ca, 200 degrees C (TAEA: (tris-aminoethyl)-amine). The compounds are charac terized by interplanar distances of 7.0, 9.5, 11.1, 13.3 and 14.3 Angstrom, respectively. They show long range magnetic ordering below 16 K, character ized by positive Weiss constants, imaginary component in the ac-susceptibil ity, spontaneous magnetisation in small applied field and coercive fields i n the range 400 to 700 Oe. The magnetisation in Geld of 3 Tesla classifies them as 3D ferromagnet.