[14p-B2-1~19] 3.9 Terahertz technologies

[14p-B2-1] [Young Scientist Presentation Award Speech] Coherent control of macroscopic spin order with intense terahertz magnetic nearfields

〇Takayuki Kurihara¹, Makoto Nakajima¹, Tohru Suemoto² (1.ILE, Osaka Univ., 2.Toyota Riken)

Keywords:intense terahertz wave, metamaterial, spintronics

Magnetic field of terahertz wave is known to couple efficiently with the spin precession dynamics in spin ordered substances, and is expected to greatly extend the available timescales of spintronics technologies up to picosecond or less. While this method has been successfully applied to probe magnetic states of various materials in either static- or small perturbation regimes, no reports has been made which realized control of macroscopic orientation in ferromagnetic permanent states, which is one of the most important aspect from the viewpoint of application such as information processing, memory device, and quantum computation.
Here we present what we believe to be the first demonstration of macroscopic control of ferromagnetic states in weak ferromagnet ErFeO₃. We perturbed the initial stage of laser-induced spin reorientation phase transition (SRPT) by applying intense THz magnetic nearfield enhanced around split-ring resonator (SRR) metamaterial, by which means one of the two otherwise degenerate final-state magnetization states (up- and down spin states) was coherently selected at an unprecedented amount of magnetization ever reported. Our results pave way towards realization of future ultrafast spintronics memory devices operating beyond the spin precession timescale and below the sub-diffraction spatial resolution