Figure 1

Schematic illustrations of (a) the cation sublattice and (b) the MnO${}_6$ and TiO${}_6$ octahedra of MnTiO${}_3$. (c) The collinear spin structure along the $c$ axis with $H\parallel c$ and $H<H_c$. (d) A proposed noncollinear spin structure with spins canting to the $a$ axis with $H\parallel c$ and $H>H_c$. (e) The temperature dependence of magnetic susceptibility and specific heat. The inset shows the phase diagram of MnTiO${}_3$ (adapted from Fukata et al.[29]). (f) The magnetic field dependence of magnetization and the derivative of magnetization along the $c$ axis at $T$ $=$ 1.4 K.Reuse & Permissions

Figure 2

The room-temperature SHG spectrum of MnTiO${}_3$ (black line) in the 1.77–3.74 eV range with linearly polarized light (k $\parallel$ $c$ axis). The SHG peaks represent the various optical transitions from the ground state of high-spin Mn${}^{2+}$ cations in a trigonally distorted octahedral crystal field (${}^6{A}_{1g}$) to the excited states as shown in the high-spin 3$d$${}^5$ Tanabe-Sugano energy level diagram. The small SHG peak at 2.19 eV is a background artifact. Absorbance spectra using unpolarized light (k $\parallel$ $c$ axis) at room temperature and 4 K show the ${}^6{A}_{1g}$ to ${}^4{T}_{1g}$ peak at a higher energy compared to the corresponding SHG peak. The inset shows a collective excitation at 2 eV in the 4 K absorbance spectrum.Reuse & Permissions

Figure 3

Circularly polarized (k $\parallel$ $c$ axis) SHG spectra in the (a) paramagnetic phase, (b) AFM phase, and (c) spin-flop phase. (d) Percent change between the left and right circular polarization SHG intensity for the three phases. At a specific point within the resonance, the difference became negligible for the paramagnetic and spin-flop phases, while in the zero-field AFM phase, the circular intensity difference remained nonzero. Error bars show the standard deviation of observations. Small variations in the absolute SHG intensities between (a), (b), and (c) could not be verified and so were removed by normalization. The variation in the line shape of (c) from (a) and (b) was caused by a small, unavoidable change in the spectrum of the exciting fundamental needed to maintain the required power output. Panels (e) and (f) show the temperature and magnetic field dependences of the percent change of circularly polarized SHG intensity, respectively.Reuse & Permissions