Thermally driven commensurate-incommensurate transition tracked by magnetochromism in chiral polar Ni2In0.9Cr0.1SbO6

Abstract

${\mathrm{Ni}}_{2}{\mathrm{In}}_{0.9}{\mathrm{Cr}}_{0.1}{\mathrm{SbO}}_{6}$ is a trigonal chiral polar helimagnet with multiferroic nature. Here, we perform optical absorption measurements on ${\mathrm{Ni}}_{2}{\mathrm{In}}_{0.9}{\mathrm{Cr}}_{0.1}{\mathrm{SbO}}_{6}$ in magnetic fields. The observed magnetochromism is attributed to the spin-dependent transition probability of the intra-atomic $d\text{\ensuremath{-}}d$ excitation from the ${}^{3}{A}_{2g}$ ground state to the ${}^{1}{E}_{g}$ excited state of ${\mathrm{Ni}}^{2+}$ ions with the $3{d}^{8}$ electronic configuration. Exploiting the magnetodielectric coupling in optical frequencies, we propose that the boundary between ferrimagnetic and incommensurate magnetic phases of ${\mathrm{Ni}}_{2}{\mathrm{In}}_{0.9}{\mathrm{Cr}}_{0.1}{\mathrm{SbO}}_{6}$ in 6 T along the $c$ axis should lie at around 50 K.