Magnetic property of Ba2CoGe2O7

A two-dimensional antiferromagnet (S = 3/2), Ba2CoGe2O7, was studied, which is isostructural to S = 1/2 spiral antiferromagnet, Ba2CuGe2O7. A single crystal of Ba2CoGe2O7 was grown and its magnetization was measured. A weak ferromagnetism was observed at 6.7 K, while the spiral antiferromagnetism was reported in Ba2CuGe2O7. The origin of the ordered states in these isostructural materials are Dzyaloshinskii-Moriya interaction and the change of the direction of D vector results in the different spin configurations. We have also synthesized polycrystalline samples of Ba2Cu1-xCoxGe2O7, and observed the change of the ordered state with x. (C) 2003 Elsevier Science B.V. All rights reserved.