Ga${}^{3+}$-substitution effects in the weak ferromagnetic oxide LaCo${}_{0.8}$Rh${}_{0.2}$O${}_3$

Abstract

Magnetization and x-ray diffraction have been measured on polycrystalline samples of LaCo${}_{0.8-y}$Rh${}_{0.2}$Ga${}_y$O${}_3$ for $0\le y\le 0.15$ in order to understand the spin state of Co${}^{3+}$ through the Ga${}^{3+}$ substitution effect. The ferromagnetic order in LaCo${}_{0.8}$Rh${}_{0.2}$O${}_3$ below 15 K is dramatically suppressed by the Ga${}^{3+}$ substitution, where the ferromagnetic volume fraction is linearly decreased. The normal state susceptibility also systematically decreases with the Ga content, from which we find that one Ga${}^{3+}$ ion reduces 4.6 ${\mu }_{\mathrm{B}}$ per formula unit. We have evaluated how the concentration of the high-spin state Co${}^{3+}$ changes with temperature by using an extended Curie-Weiss law, and have found that the substituted Rh${}^{3+}$ ion stabilizes the high-spin state Co${}^{3+}$ ion down to low temperatures. We find that Ga${}^{3+}$ preferentially replaces the high-spin state Co${}^{3+}$, which makes a remarkable contrast to our previous finding that Rh${}^{3+}$ preferentially replaces the low-spin state Co${}^{3+}$. These results strongly suggest that the magnetically excited state of LaCoO${}_3$ at room temperature is a mixed state of high-spin state Co${}^{3+}$ and low-spin state Co${}^{3+}$.

5 pages, 6 figures

References in corpus (2)

• The spin state transition in LaCoO${}_3$; revising a revision
• Spin-state polaron in lightly hole-doped LaCoO_3

Cited by in corpus (1)

• Unconventional magnetism in the layered oxide LaSrRhO${}_4$