Electron Transport Properties of Fe-Doped Bi-Layered Managnites La1.6Dy0.2Sr1.2Mn2-xFexO7

The effect of Fe on the electron transport and magnetoresistive properties of layered perovskite manganites La
_1.6
Dy
_0.2
Sr
_1.2
Mn
_{2 - x}
Fe
_x
O
₇
, which consists of two [MnO
₂
] layers intertwined with a rock-salt type layer of [(La,Dy,Sr)
₂
O
₂
] have been investigated. The metal-insulator (M-I) transition and magnetoresistance phenomena were observed. The substitution of Mn by Fe decreases M-I transition temperature. As the ionic radii of Mn
³⁺
and Fe
³⁺
are similar for low Fe content samples, the crystal distortion induced by Fe substitution is not obvious. But the substitution of Mn by Fe suppresses the double-exchange interaction, weakness the ferromagnetism and consequently decreases the M-I transition temperature. The substitution of Fe also causes a depletion of the Mn
³⁺
/Mn
⁴⁺
ratio and the population of the hopping electrons that ultimately reduces metallic conduction. The polycrystalline samples exhibit a sharp drop in the magnetoresistance at low magnetic fields