Effect of magnetic coupling on the magnetoresistive properties in La0.67Sr0.33MnO3 ÕBaFe11.3„ZnSn...0.7O19 composites

The La0.67Sr0.33MnO3 /BaFe11.3~ZnSn!0.7O19 ~LSMO/BaM! composites have been prepared by cosintering the LSMO and the BaM powders. The microstructural, magnetic, and magnetoresistive ~MR! properties of those systems were systematically studied. Due to the magnetic coupling between the LSMO ~a soft magnet metal! and BaM ~a hard magnet insulator! grains, the low-field MR sensitivity was reduced and the high-field MR slope was enhanced for the composites. In addition, an abnormal MR hysteresis ~resistance reaches its maximum before field reversal! was identified for the composite when the field is applied vertical to the sample plane. Its origin was attributed to a coplay of the LSMO/BaM spin coupling and the demagnetization effect. Finally, an anisotropic magnetoresistance ~AMR! effect was observed in the composites. The AMR value decreased with increasing the BaM content, which can be explained by the changes of the local effective field on the grain boundaries. © 2001 American Institute of Physics. @DOI: 10.1063/1.1392962#