ENHANCED MAGNETORESISTIVE EFFECT IN TRILAYERED FILMS OF LaCaMnO/LaNdCaMnO/LaCaMnO

A series of La 0.67 Ca 0.33 MnO 3 /(La 0.35 Nd 0.65 ) 2/3 Ca 1/3 MnO 3 /La 0.67 Ca 0.33 MnO 3 (termed as LCMO/LNCMO/LCMO) epitaxial trilayered films, in which LNCMO under zero magnetic field exhibits semiconductor-like conducting behavior down to 4.2K, have been fabricated on SrTiO 3 (001) substrates by d.c. magnetron sputtering technique. The measurements of resistance show that transport properties of the trilayered films are clearly different from that of the pure LNCMO or LCMO films. In the LCMO(75nm)/LNCMO(450nm)/LCMO(75nm)film, two resistance peaks have been observed. With the measurements of magnetic hysteresis loop, it show that there may exist a magnetic exchange-coupling interaction and an intra-magnetic field in the trilayered film. When the external magnetic field is applied, the resistance decreases and the resistance peak shifts to higher temperature, therefore it appears colossal magnetoresistance effect. Compared with the magnetoresistance response in pure LCMO film, the enhanced magnetoresistance effect have been observed in these trilayed films, and it maintains a stronger magnetoresistance effect in a wide temperature range. We suggest it results from the middle layer LNCMO in the trilayered film.