We have studied a nearly stoichiometric insulating ${\mathrm{Y}}_{0.97\left(2\right)}{\mathrm{Cr}}_{0.98\left(2\right)}{\mathrm{O}}_{3.00\left(2\right)}$ single crystal by performing measurements of magnetization, heat capacity, and neutron diffraction. Albeit that the $\mathrm{Y}\mathrm{Cr}{\mathrm{O}}_3$ compound behaves like a soft ferromagnet with a coersive force of $\sim 0.05$ T, there exist strong antiferromagnetic (AFM) interactions between ${\mathrm{Cr}}^{3+}$ spins due to a strongly negative paramagnetic Curie-Weiss temperature, i.e., $-433.2$(6) K. The coexistence of ferromagnetism and antiferromagnetism may indicate a canted AFM structure. The AFM phase transition occurs at $T_{\text{N}}=141.5\left(1\right)\mathrm{K}$, which increases to $T_{\text{N}}$(5 T) = 144.5(1) K at 5 T. Within the accuracy of the present neutron-diffraction studies, we determined a G-type AFM structure with a propagation vector k = (1 1 0) and ${\mathrm{Cr}}^{3+}$ spin directions along the crystallographic $c$ axis of the orthorhombic structure with space group $Pnma$ below $T_{\text{N}}$. At 12 K, the refined moment size is 2.45(6) ${\mu }_{\text{B}}, \sim 82\%$ of the theoretical saturation value $3{\mu }_{\text{B}}$. The ${\mathrm{Cr}}^{3+}$ spin interactions are probably two-dimensional Ising like within the reciprocal (1 1 0) scattering plane. Below $T_{\text{N}}$, the lattice configuration ($a$, $b$ , $c$ , and $V$ ) deviates largely downward from the Grüneisen law, displaying an anisotropic magnetostriction effect and a magnetoelastic effect. Especially, the sample contraction upon cooling is enhanced below the AFM transition temperature. There is evidence to suggest that the actual crystalline symmetry of $\mathrm{Y}\mathrm{Cr}{\mathrm{O}}_3$ compound is probably lower than the currently assumed one. Additionally, we compared the $t_{2\text{g}}\mathrm{Y}\mathrm{Cr}{\mathrm{O}}_3$ and the $e_{\text{g}}{\mathrm{La}}_{7/8}{\mathrm{Sr}}_{1/8}{\mathrm{MnO}}_3$ single crystals for a further understanding of the reason for the possible symmetry lowering.

中文翻译：

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钇-氧化铬中的晶体和磁性结构，磁化，热容和各向异性磁致伸缩效应

我们研究了一种接近化学计量的绝缘 ${\mathrm{ÿ}}_{0.97（2）}{铬}_{0.98（2）}{\mathrm{Ø}}_{3.00（2）}$通过测量磁化强度，热容和中子衍射来形成单晶。尽管$\mathrm{ÿ}铬{\mathrm{Ø}}_3$ 化合物的行为像软铁磁体，矫顽力为 $〜0.05$ T之间存在强反铁磁（AFM）相互作用 ${铬}^{3+}$ 由于强负顺磁居里-魏斯温度（即 $-433.2$（6）K.铁磁性和反铁磁性的共存可能表明AFM结构倾斜。AFM相变发生在${Ť}_{\text{ñ}}=141.5（\mathrm{1个}）\mathrm{ķ}$，增加到 ${Ť}_{\text{ñ}}$在5 T时（5 T）= 144.5（1）K。在当前中子衍射研究的准确性范围内，我们确定了一种G型AFM结构，其传播矢量k =（1 1 0）并且${铬}^{3+}$ 沿晶体自旋方向 $C$ 具有空间群的正交结构的轴 $Pñ米\mathrm{一种}$ 下面 ${Ť}_{\text{ñ}}$。在12 K时，精确力矩大小为2.45（6）${\mu }_{\text{乙}}， 〜82％$ 理论饱和值的 $3{\mu }_{\text{乙}}$。的${铬}^{3+}$自旋相互作用可能是二维Ising，就像在倒数（1 1 0）散射平面内一样。下面${Ť}_{\text{ñ}}$，晶格配置（$\mathrm{一种}$， $b$ ， $C$ 和 $V$ ）在很大程度上偏离Grüneisen定律，表现出各向异性的磁致伸缩效应和磁弹性效应。尤其是，在低于AFM转变温度时，冷却后的样品收缩会增强。有证据表明实际的晶体对称性$\mathrm{ÿ}铬{\mathrm{Ø}}_3$化合物可能低于当前假定的化合物。此外，我们比较了${Ť}_{2\text{G}}\mathrm{ÿ}铬{\mathrm{Ø}}_3$ 和 ${Ë}_{\text{G}}{啦}_{7/8}{r}_{\mathrm{1个}/8}{\mathrm{二氧化锰}}_3$ 单晶，以进一步了解可能降低对称性的原因。