A NEW 2-DIMENSIONAL MAGNETIC MODEL FOR THE LAYERED COMPOUNDS OF FEMO(4)CL (M=MO AND W) WITH STRONG INTERLAYER COUPLING

Low dimensional magnetic properties of the layer-type compounds of FeM oO4Cl and FeWO4Cl have been systematically studied. The magnetic susce ptibility for the polycrystalline samples were measured in the tempera ture range 4K to 600K. The negative Weiss constants and broad chi-maxi mum centers at T chi max (107K for FeMoO4Cl and 74K for FeWO4Cl) under line the existence of low dimensional antiferromagnetic exchange inter action among the paramagnetic ferric ions. The intra and interlayer ex change parameters (J and J') have been determined from the simple comb inative form of <chi> = a chi(2D) + (1-a)chi(1D) based upon the high t emperature series expansion methods for the case of S=5/2 quadratic an d linear chain Heisenberg antiferromagnetic model. The ratio of interl ayer 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 structu re. (2+1) dimensional magnetic interactions are discussed in view of c rystal structure and chemical bonding.