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

Magnetization, ac initial magnetic susceptibility, resistance, magnetoresistance, thermal expansion and magnetostriction measurements are made on R1−xSrxMnO3 (R=Sm, x=0.33, 0.40, 0.45; R=Nd, x=0.33, 0.45) compounds. For all compounds in the TC region we observe a large volume contraction ΔV/V≈0.1% and unusual behavior of the volume magnetostriction ω, namely, a peak of anomalous magnitude of negative volume magnetostriction on the ω(T) curve. We obtain a giant negative volume magnetostriction of ∼5×10−4 at a relatively low magnetic field B=0.9 T and ∼10−3 at a high magnetic field B=13 T for Sm samples. The magnetostriction of Nd compounds is one order of magnitude less. For all compounds the giant magnetostriction is accompanied by colossal negative magnetoresistance 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 the framework of an electronic phase separation model.