A new 2-dimensional magnetic model for the layered compounds of FeMO4Cl(M=Mo and W) with strong interlayer coupling

Low dimensional magnetic properties of the layer-type compounds of FeMoO4Cl and FeWO4Cl have been systematically studied. The magnetic susceptibility for the polycrystalline samples were measured in the temperature range 4K to 600K. The negative Weiss constants and broad χ-maximum centers at Tχmax (107K for FeMoO4Cl and 74K for FeWO4Cl) underline the existence of low dimensional antiferromagnetic exchange interaction among the paramagnetic ferric ions. The intra and interlayer exchange parameters (J and J′) have been determined from the simple combinative form of 〈χ〉 = aχ2D + (1-a)χ1D based upon the high temperature series expansion methods for the case of S=52 quadratic and linear chain Heisenberg antiferromagnetic model. The ratio of interlayer to intralayer exchange parameters , |J′/J|, has been estimated as 0.59 and 0.34 for FeMoO4Cl and FeWO4Cl, respectively, which indicates the strong interlayer magnetic coupling even in such a layered structure. (2+1) dimensional magnetic interactions are discussed in view of crystal structure and chemical bonding.