STRUCTURAL, MAGNETIC AND MOSSBAUER STUDIES OF THE MOLECULAR FERROMAGNET COMPOUNDS NBU(4)[MCR(C2O4)(3)](BU=(CH2)(3)CH3, M=MN, FE)

An X-ray study of a single crystal of the NBu(4)[MnCr(C2O4)(3) composi tion reveals a layered structure with an ordered arrangement of Mn2+ a nd Cr3+ ions. According to the data of the orientation dependence of m agnetization at 4.5K, the magnentic easy axis is aligned along the cry stal c-axis. Mossbauer data analysis of isostructural NBu(4)[FeCr(C2O4 )(3)] powder material gives, on the contrary, the evidence of strong c onfinement of Fe2+ spins to the crystal basal plane. The ferromagnetic system which arises here is a quasi-2D system in terms of the nature of its exchange interactions.