Possible magnetic phase separation in Ru-doped La0.67Ca0.33MnO3

Abstract X-ray diffraction, resistivity, AC susceptibility and magnetization studies on La 0.67 Ca 0.33 Mn 1− x Ru x O 3 (0⩽ x 3+ and Ru 4+ . The resistivity of the doped compounds exhibited two features: a broad hump and a relatively sharp peak. While a para- to ferromagnetic transition could be observed for the latter peak, no magnetic signal either in AC susceptibility or in magnetization measurements could be observed for the broad hump. The magnetic moment of Mn per unit cell decreases non-linearly from 3.55 to 3  μ B for the Ru compositions studied. Based on the results of the present studies and existing literature on Mn-site substituted systems, we argue that a magnetic phase separation occurs in the Ru-doped system. While the sharp peak in the resistivity corresponds to Ru 4+ -enriched regions with ferromagnetic coupling of Ru with the neighboring Mn ions, the broad peak corresponds to Ru 3+ -rich regions, with antiferromagnetic coupling of Ru with the neighboring Mn ions.