Crucial roles of phase competition and spin-lattice relaxation in gigantic switchable optomagnet effect of (Fe_0.875Zn_0.125)₂Mo₃O₈

Yao-Hua Zhuang^1*, H. W. Liu¹, Y. H. Li¹, Y. M. Chang¹, T. Kurumaji², Y. Tokura^3,4, Y. M. Sheu^1,5

¹Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
²Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
³Center for Emergent Matter Science (CEMS), RIKEN, Wako, Saitama, Japan
⁴Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), University of Tokyo, Tokyo, Japan
⁵Center for Emergent Functional Matter Science,, National Yang Ming Chiao Tung University, Hsinchu, Taiwan

* Presenter:Yao-Hua Zhuang, email:jack94319579@gmail.com

It has been discovered that crystal field excitations with spin-flip transition is a key to controlling switchable optomagnet effects in antiferromagnetic (Fe0.875Zn0.125)2Mo3O8. However, when the flipped spins are in excited states to frustrate the balanced spin moments, the photoinduced magnetization has not occurred yet. Only after ultrashort pulses disappears does the gigantic magnetization starts to grow from zero moment. To construct a detailed picture of crystal field excitation, we design the experiment to compare cases between Néel axis perpendicular and parallel to the angular momentum of circularly polarized light. With aids of Kerr effect microscopy and applications of magnetic field, we uncover all indispensable factors for the gigantic optomagnet effect and discern photoinduced switchable magnetization from non-switchable demagnetization. Our experimental designs, while rarely explored, is critical for developments of antiferromagnetic memory devices using insulating oxides.

Keywords: optomagnet effect, phase competition, crystal field excitation