Optical Observation of Stress-Induced Spin Flop inCr2O3

It has been observed that applying sufficiently large uniaxial stress to ${\mathrm{Cr}}_2$ ${\mathrm{O}}_3$ induces in its ${}_{}{}^4{}_{}{}^{}A_2^{}{}_{}{}^{}\to {}_{}{}^2{}_{}{}^{}E$ optical-exciton absorption spectrum changes that are nearly identical to those observed when magnetic-field—induced spin flop occurs. This is interpreted as evidence that uniaxial stress induces spin flop in ${\mathrm{Cr}}_2$ ${\mathrm{O}}_3$. A phenomenological discussion is given.