Crucial roles of phase competition and spin-lattice relaxation in the gigantic switchable optomagnet effect of (Fe0.875Zn0.125)2Mo3O8

It was discovered that crystal-field excitations involving spin-flip transitions play a crucial role in controlling switchable optomagnet effects in antiferromagnetic ${({\mathrm{Fe}}_{0.875}{\mathrm{Zn}}_{0.125})}_{2}{\mathrm{Mo}}_{3}{\mathrm{O}}_{8}$. However, when the flipped spins are in excited states to frustrate the balanced spin moments, the photoinduced magnetization has not occurred yet. Only after the ultrashort pulses disappear does the gigantic magnetization start to grow from a zero moment. In this study, we demonstrate that the gigantic optomagnetic effect is triggered by a two-step spin-flip process. Through the use of Kerr-effect microscopy and applications of the magnetic field, we discern between photoinduced switchable magnetization and nonswitchable demagnetization. Our experimental designs uncover all indispensable factors for the development of antiferromagnetic memory devices using insulating oxides.