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The magnetic structures of a number of single and mixed spinel ferrites have been determined using the polarised neutron diffraction technique. It is shown that this method is applicable even when the structure is noncollinear. The experimental magnetization curves in MgFe2O4 have been fitted to a molecular field expression to derive the dominant exchange interactions as JAB = — 22 °K and JAA = — 4 °K. From paramagnetic neutron Scattering, the only dominant exchange interactions in ZnFe2O4 and ZnCr2O4 have been determined as JBB (Fe3+-Fe3+) = 1.04 °K and JBB (Cr3+-Cr3+) = 2.38 °K. In MnAl2O4 (9 % inverted) JAA (Mn2+-Mn2+) = — 0.21 °K, JAB (Mn2+-Mn2+) = — 16 °K