High-pressure synthesis and structural, transport, and magnetic properties of rutile-type Cr2ReO6 and CrReO4

Abstract

We have synthesized the cation ordered rutile-type $\mathrm{C}{\mathrm{r}}_{2}\mathrm{Re}{\mathrm{O}}_{6}$ and $\mathrm{CrRe}{\mathrm{O}}_{4}$ under high-pressure and high-temperature conditions and performed detailed characterizations on their structural, transport, and magnetic properties via x-ray and neutron powder diffraction, resistivity, magnetic susceptibility, and specific heat measurements. $\mathrm{C}{\mathrm{r}}_{2}\mathrm{Re}{\mathrm{O}}_{6}$ crystallizes in the inverse trirutile structure with lattice parameters $a=b=4.552\phantom{\rule{0.16em}{0ex}}21(5)\phantom{\rule{0.16em}{0ex}}\AA{}$ and $c=8.8934(1)\phantom{\rule{0.16em}{0ex}}\AA{}$ in the space group $P{4}_{2}/mnm$. It undergoes a second-order antiferromagnetic transition at ${T}_{\mathrm{N}}\ensuremath{\approx}67\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ with the magnetic structure described by the propagation vector $\mathbf{k}=[0.5,0,0.5]$. For $\mathrm{CrRe}{\mathrm{O}}_{4}$, it adopts a monoclinically distorted rutile-like structure with unit-cell parameters $a=9.3393(2)\phantom{\rule{0.16em}{0ex}}\AA{}$, $b=5.6869(1)\phantom{\rule{0.16em}{0ex}}\AA{}$, $c=4.6243(1)\phantom{\rule{0.16em}{0ex}}\AA{}$, and $\ensuremath{\beta}=92.043{(8)}^{\ensuremath{\circ}}$ in the space group $C2/m$. It also exhibits an antiferromagnetic order at ${T}_{\mathrm{N}}=98\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ with the magnetic structure described by the propagation vector $\mathbf{k}=[1,0,0.5]$. Interestingly, a large paramagnetic Weiss temperature of ${\ensuremath{\theta}}_{\mathrm{CW}}=\ensuremath{-}478\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ is evidenced from the Curie-Weiss fitting to the inverse magnetic susceptibility. The temperature dependence of resistivity \ensuremath{\rho}($T$) for both compounds can be described with Mott's variable range hopping mechanism in the one-dimensional model for $\mathrm{C}{\mathrm{r}}_{2}\mathrm{Re}{\mathrm{O}}_{6}$ and the three-dimensional model for $\mathrm{CrRe}{\mathrm{O}}_{4}$, respectively. For both compounds, a weak resistivity anomaly can be discerned around ${T}_{\mathrm{N}}$ from the temperature derivative curves, signaling the interplay of charge and spin degrees of freedom for these $3d$(Cr)-$5d$(Re) coupled electron systems.