Figure 1

(Color online) $300\mathrm{K}$ crystal structure of $\mathrm{Ho}\mathrm{Mn}{\mathrm{O}}_3$ showing layers of distorted $\mathrm{Mn}{\mathrm{O}}_5$ bipyramidal building block units separated by layers of ${\mathrm{Ho}}^{3+}$ ions (Refs. 10, 27). Shading of the $\mathrm{Mn}{\mathrm{O}}_5$ bipyramids indicates tilting with respect to the $c$ axis. $\mathrm{Ho}\mathrm{Mn}{\mathrm{O}}_3$ displays a $P{6}_{3}cm$ space group at $300\mathrm{K}$.Reuse & Permissions

Figure 2

(Color online) (a) $ab$-plane optical conductivity of $\mathrm{Ho}\mathrm{Mn}{\mathrm{O}}_3$ at 300 and $6\mathrm{K}$ extracted from the measured reflectance by a Kramers-Kronig analysis. The inset shows a typical peak fit of the $\mathrm{Mn}d$ to $d$ band at $6\mathrm{K}$. (b) Peak positions of model oscillators, fitted to the on-site excitations, as a function of temperature. Open and closed symbols represent the two sets of independently measured data. Error bars in the fit are on the order of the symbol size. The shaded vertical lines designate the well-known $T_N$ and $T_{SR}$ transitions. (c) Spectral weight of model oscillators as a function of temperature. The symbols in this panel correspond to those in panel (b).Reuse & Permissions

Figure 3

(Color online) (a) Schematic symmetry decent diagram showing the crystal-field splitting of the ${\mathrm{Mn}}^{3+}d$ levels in the high-temperature paraelectric state and the splitting of these energy levels due to the reduced site symmetry around the ${\mathrm{Mn}}^{3+}$ center below $T_{FE}$. (b) Distorted $\mathrm{Mn}{\mathrm{O}}_5$ trigonal bipyramid building block unit highlighting the reduced local symmetry around the ${\mathrm{Mn}}^{3+}$ center.Reuse & Permissions

Figure 4

(Color online) The high-energy dielectric contrast $\Delta {ϵ}_1∕{ϵ}_1$ of $\mathrm{Ho}\mathrm{Mn}{\mathrm{O}}_3$ in the region of the $\mathrm{Mn}d$ to $d$ excitations (a) for $T_2=85\mathrm{K}$, $T_1=65\mathrm{K}$ $(T_2>T_N>T_1)$ and (b) for $T_2=45\mathrm{K}$, $T_1=30\mathrm{K}$ $(T_2>T_{SR}>T_1)$.Reuse & Permissions

Figure 5

(Color online) (a) The $6\mathrm{K}$ normalized magneto-optical response of $\mathrm{Ho}\mathrm{Mn}{\mathrm{O}}_3$, $R\left(H\right)∕R(H=0\mathrm{T})$, in an applied magnetic field from $0\text{to}20\mathrm{T}$ $(H\Vert c)$. Data are shown in $4\mathrm{T}$ steps. (b) $ab$-plane optical conductivity for $H=0$ (solid line) and $20\mathrm{T}$ (dashed line) $(H\Vert c)$ at $6\mathrm{K}$. (c) Dielectric response for $H=0$ (solid line) and $20\mathrm{T}$ (dashed line) $(H\Vert c)$ at $6\mathrm{K}$. The inset shows a close-up view of the high-energy dielectric contrast, $\Delta {ϵ}_1∕{ϵ}_1$, which is the largest in the region of the $\mathrm{Mn}d$ to $d$ excitations.Reuse & Permissions