Magnetoresistance and magnetostriction effect of (La1−xSmx)2/3Sr1/3MnO3 manganites

A series of bulk polycrystalline (La1−xSmx)2/3Sr1/3MnO3 (x=0.0,0.2,0.4,0.6,0.7) samples were prepared by traditional solid-phase reaction method. Their structures, magnetoresistances and magnetostrictions were studied. The experimental results indicate that with the increase of the Sm content x, the average ionic radius of the A site 〈rA〉 and the Curie temperature of the samples decrease, the maximum of the zero-field resistivity at TP and corresponding magnetoresistance increase. The magnetostriction measurement shows that the anisotropic magnetostriction coefficient λt are nearly zero, while the volume magnetostriction coefficients are negative for the x=0.6 and 0.7 samples, which implies that the volumes of the samples are contracted at the temperature just below the Curie temperature, and no saturation occurred even under 7 T strong magnetic field. For the x=0.6 sample, the maximum of ω is −550×10−6 in the magnetic field of 7 T at 210 K. These experimental results can be interpreted by the viewpoint of phase separation due to the substitution of Sm3+ with smaller ionic radius for La3+ with larger ionic radius in the samples.