Colossal magnetoresistance in La 2−2 xSr 1+2 xMn 2O 7 single crystals

Abstract

We performed magnetisation ( M) and transport measurements along the ab plane and the c direction in La 2−2 x Sr 1+2 x Mn 2O 7 single crystals for x=0.4. In addition to a sharp para-ferromagnetic transition at T c =125 K , a weak maximum in M was found around 265 K. A sharp drop of resistivity at T c associated with a semi-conductor to metal transition was found for both current orientations. The colossal magnetoresistance of the compound CMR=−( ρ H − ρ 0)/ ρ 0 was found to be ∼100% in a field of 8 T near T c. In contrast with the well-known La 1− x Sr x MnO 3 type manganites, a CMR effect larger than 10% was present at all temperatures ranging between 5 and 300 K.