Structural and physical properties of $SrMn_{1-x}Ru_xO_3$ perovskites

TL;DR

This study maps the structural, magnetic, and transport properties of SrMn$_{1-x}$Ru$_x$O$_3$ perovskites across the entire substitution range, revealing various magnetic phases and transitions driven by Ru substitution and disorder.

Contribution

It provides a comprehensive phase diagram of SrMn$_{1-x}$Ru$_x$O$_3$ perovskites combining neutron diffraction, magnetic, and transport data, highlighting the effects of Ru substitution on magnetic order and lattice distortion.

Findings

Antiferromagnetic C-type order for 0.06 ≤ x ≤ 0.5

First-order magnetic and resistive transitions for 0.06 ≤ x ≤ 0.2

Ferromagnetism in heavily substituted samples due to Ru$^{4+}$ exchange interactions

Abstract

We combine the results of magnetic and transport measurements with neutron diffraction data to construct the structural and magnetic phase diagram of the entire family of SrMn$_{1-x}$Ru$_{x}$O$_3$ ($0 \leqslant x \leqslant 1$) perovskites. We have found antiferromagnetic ordering of the C type for lightly Ru-substituted materials ($0.06 \leqslant x \leqslant 0.5$) in a similar manner to $R_{y}$Sr$_{1-y}$MnO$_3$ ($R$=La, Pr), due to the generation of Mn$^{3+}$ in both families of manganite perovskites by either $B$-site substitution of Ru$^{5+}$ for Mn$^{4+}$ or $A$-site substitution of $R^{3+}$ for Sr$^{2+}$. This similarity is driven by the same ratio of $d^4$ / $d^3$ ions in both classes of materials for equivalent substitution level. In both cases, a tetragonal lattice distortion is observed, which for some compositions ($0.06 \leqslant x \leqslant 0.2$) is coupled to a C-type AF transition and results in a first order magnetic and resistive transition. Heavily substituted SrMn$_{1-x}$Ru$_{x}$O$_3$ materials are ferromagnetic due to dominating exchange interactions between the Ru$^{4+}$ ions. Intermediate substitution ($0.6 \leqslant x \leqslant 0.7$) leads to a spin-glass behavior instead of a quantum critical point reported previously in single crystals, due to enhanced disorder.