SLOW PARAMAGNETIC RELAXATION AND MAGNETIC SPLITTINGS IN MOSSBAUER-SPECTRA OBSERVED FOR MIXED-METAL ASSEMBLIES (NBU(4)MFE(OX)(3))(X) (NBU(4)(-BUTYL)AMMONIUM ION, OX(2-) EQUALS OXALATE ION, M=ZN2+, NI2+, MN2+)()EQUALS TETRA(N)

Magnetic interactions in the lattices of oxalate-bridged metal complex es {NBu(4)MFe(ox)(3)}(x) (M=Zn2+ (i), Ni2+ (2), Mn2+ (3)) have been in vestigated by using Fe-57 Mossbauer spectroscopy, where NBu(4)(+)=tetr a(n-butyl) ammonium ion, ox(2-)=oxalate ion. Compound 1, a paramagnet, showed apparently a broad single peak of asymmetry in its Mossbauer s pectrum, based on the slow paramagnetic relaxation process of the elec tron spin of Fe3+ in 1. Rapid development of nuclear Zeeman splittings was observed in the spectra of 2 and 3 on lowering the temperature be low similar to 25 K, which indicated the occurrence of three-dimension al magnetic ordering in these compounds under zero applied field. The estimated values of the internal magnetic field (509 kOe for 2 and 503 kOe for 3 at 4.2 K) were typical of high-spin Fe3+.