Giant volume magnetostriction in CMR manganites R1-xSrxMnO3 (R=Sm, Nd)

Magnetization, ac initial magnetic susceptibility, resistance, magnetoresis tance, thermal expansion and magnetostriction measurements are made on R1-x SrxMnO3 (R=Sm, x=0.33, 0.40, 0.45; R=Nd, x=0.33, 0.45) compounds. For all c ompounds in the T-C region we observe a large volume contraction DeltaV/V a pproximate to0.1% and unusual behavior of the volume magnetostriction omega , namely, a peak of anomalous magnitude of negative volume magnetostriction on the omega (T) curve. We obtain a giant negative volume magnetostriction of similar to 5x10(-4) at a relatively low magnetic field B=0.9 T and simi lar to 10(-3) at a high magnetic field B=13 T for Sm samples. The magnetost riction of Nd compounds is one order of magnitude less. For all compounds t he giant magnetostriction is accompanied by colossal negative magnetoresist ance equal to 78, 72, and 44% at B=0.9 T for Sm compounds with x=0.33, 0.40 , and 0.45, respectively. All of the observed properties are explained in t he framework of an electronic phase separation model. (C) 2001 American Ins titute of Physics.