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Magnetic properties and electrical conductivity were measured on polycrystalline Lu 2 Fe 3 O 7 from 4.2 K to 650 K and were compared with those of LuFe 2 O 4 . The electrical conductivity, the magnetic susceptibility per Fe at low temperatures and the induced moment per formula unit are nearly the same for both materials. It is concluded that Lu 2 Fe 3 O 7 is constructed by an alternate stacking of Lu 3+ Fe 2 2.5+ O 4 and Lu 3+ Fe 3+ O 3 and that the magnetic moment is induced by the field cooling mainly in the former part. The origin of the moment induction (parasitic ferrimagnetism) is discussed briefly.

Magnetic and Mossbauer measurements were done between 77 and 300 K on polycrystalline sample of YFe 2 O 4 (Y 3+ Fe 2+ Fe 3+ O 4 2- ). This compound shows an “induced parastic ferromagnetism”: Weak ferromagnetic moment (∼2 emu/g) was induced below 240 K by applying external field (∼7 kOe) and an uniaxial anisotropy was induced by cooling the sample from 300 K to 77 K in the presence of external field. Mossbauer spectrum of Fe 57 showed a magnetic pattern with internal field of ca. 460 kOe at 90 K, and showed a paramagnetic one at 300 K.