Magnetic dilution of a honeycomb lattice XY magnet CoTiO3.

We report our study of cobalt (II) titanate, CoTiO3, in which magnetic Co ions are replaced by non-magnetic ions. The antiferromagnetic ordering transition of CoTiO3around 37 K is described with ferromagnetic honeycomb layers coupled antiferromagnetically along the crystallographicc-direction. The effect of magnetic dilution on the Néel temperature of this material is investigated through the doping of Zn2+and Mg2+in place of Co2+for various dilution levels up tox+y= 0.46 in Co1-x-yZnxMgyTiO3. Single phase polycrystalline samples have been synthesized and their structural and magnetic properties have been examined. A linear relation between dilution and the Néel temperature is observed over a wide doping range. A linear extrapolation would suggest that the required dilution level to suppress magnetic order is aroundx+y∼ 0.74, well beyond the classical percolation threshold. The implication of this observation for microscopic models for describing CoTiO3is discussed.