Enhanced magnetism and suppressed magnetoelastic coupling induced by electron doping in Ca${}_{1-x}$Y${}_x$MnReO${}_6$

Abstract

The Ca${}_2$MnReO${}_6$ double perovskite is a spin-orbit-assisted Mott insulator with exotic magnetic properties, including a largely non-collinear Mn${}^{2+}$ spin arrangement and nearly orthogonal coupling between such spins and the much smaller Re $5d$ magnetic moments. Here, the electron-doped compound Ca${}_{1.7}$Y${}_{0.3}$MnReO${}_6$ is investigated. Neutron and X-ray powder diffraction confirm that nearly full chemical order is maintained at the Mn and Re sites under the Y substitution at the Ca site. X-ray absorption measurements and an analysis of the Mn-O/Re-O bond distances show that the Mn oxidation state remains stable at +2 whereas Re is reduced upon doping. The electron doping increases the magnetic ordering temperature from $T_c=121$ to $150$ K and also enhances significantly the ferromagnetic component of the Mn spins at the expense of the antiferromagnetic component at the base temperature ($T=3$ K). The lattice parameter anomalies at $T_c$ observed in the parent compound are suppressed by the electron doping. The possible reasons for the enhanced magnetism and the suppressed magnetoelastic coupling in Ca${}_{1.7}$Y${}_{0.3}$MnReO${}_6$ are discussed.

Article: 14 pages, 6 figures. Appendix: 5 pages, 5 figures. Submitted to Journal of Physics: Condensed Matter

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