We have studied the magnetic properties of Ba-doped layered cobalt oxysulfide (Sr,Ba)2Cu2CoO2S2 with CoO2 squre-planes. The antiferromagnetic nature was considered to originate from the CoO2 layer dominantly. However, the effect of the inter-layer of CoO2 planes has not been clear. We therefore synthesized polycrystalline (Sr, Ba)2Cu2CoO 2S2, and investigated the effect of inter-layer distance on the magnetic properties in detail. When Sr was substituted by Ba, the difference between zero-field-cooled and field-cooled magnetization was found to decrease clearly, and such difference was ascribed to reflect the increase of the distance between CoO2 layers owing to the difference of the ionic radii between smaller Sr and lager Ba. There is a possibility that two dimensional magnetic order has strengthened.
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