Possible Magnetic separation in Ru doped La0.67Ca0.33MnO3

TL;DR

This study investigates Ru doping in La0.67Ca0.33MnO3, revealing magnetic phase separation and potential for magnetic separation techniques based on distinct magnetic and resistive features.

Contribution

It provides evidence for magnetic phase separation in Ru-doped La0.67Ca0.33MnO3, linking resistivity features to different valence states and magnetic couplings, a novel insight in this material system.

Findings

Magnetic phase separation occurs in Ru-doped La0.67Ca0.33MnO3.

Resistivity shows a broad maximum and a sharp peak linked to different Ru valence states.

Sharp peak corresponds to Ru4+ regions with ferromagnetic coupling; broad peak to Ru3+ regions with antiferromagnetic coupling.

Abstract

X-ray diffraction, resistivity, ac susceptibility and magnetization studies on La0.67Ca0.33Mn1-xRuxO3 (0 x < 0.1) were carried out. A significant increase in the lattice parameters indicated the presence of mixed valance state of Ru: Ru3+ and Ru4+. The resistivity of the doped compounds exhibited two features: a broad maximum 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 maximum. The magnetic moment decreases non linearly from 3.55 to 3 mB over the Ru composition from 0 to 8.5 at.%. Based on the results of the present studies and on existing literature on the 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 region with a ferromagnetic coupling with neighboring Mn ions, the broad peak corresponds to a Ru3+ rich regions, with an antiferromagnetic coupling with neighboring Mn ions.