Possible magnetic phase separation in Ru-doped La_0.67Ca_0.33MnO₃

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• 作者：Seetha Lakshmi ; L. ; Sridharan ; V. ; Natarajan ; D.V. ; Chandra ; Sharat ; Sankara Sastry ; V. ; Radhakrishnan ; T.S. ; et. al.
• 关键词：75.30.Vn ; Manganites ; Transport properties ; Mn-site substitution ; Inhomogeneties ; Magnetic phase separation
• 刊名：Journal of Magnetism and Magnetic Materials
• 出版年：2003
• 出版时间：February, 2003
• 年：2003
• 卷：257
• 期：2-3
• 页码：195-205
• 全文大小：642 K

文摘

X-ray diffraction, resistivity, AC susceptibility and magnetization studies on La_0.67Ca_0.33Mn_1−xRu_xO₃ (0≤x<0.085) were carried out. A significant increase in the lattice parameters indicated the presence of mixed valence state of Ru: Ru³⁺ and Ru⁴⁺. 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 3μ_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 Ru⁴⁺-enriched regions with ferromagnetic coupling of Ru with the neighboring Mn ions, the broad peak corresponds to Ru³⁺-rich regions, with antiferromagnetic coupling of Ru with the neighboring Mn ions.