SIMULTANEOUS OBSERVATION OF TUNNEL-TYPE GMR AND INTRINSIC CMR IN NANOMETER PEROVSKITE

The nanometer-sized perovskite La0.85Sr0.15SMnO3 is synthesized by a s ol-gel method. And, through controlling the conditions of heat-treatme nt, a series of polycrystalline perovskite with different grain sizes is obtained. The resistance measurements with changing temperatures sh ow that with the increase in grain size the transport properties of th is kind of granular perovskite, including the giant magnetoresistance (GMR) effect, systematically change from an interfacial effect-control led form to the crystal intrinsic type. Meanwhile, the magnetoresistan ce effect transforms from an interfacial tunneling GMR to the intrinsi c colossal magnetoresistance (CMR). For the sample with a suitable gra in size (similar to 100 nm), the two magnetoresistance effects can be observed simultaneously. And the action of both magnetoresistances in common can make a ''plain'' on the curve of magnetoresistance versus t emperature (MRT); that is, the magnetoresistance effect of the granula r perovskite does not change with temperature in a wide range.