High bandwidth THz polarization modulation of Inverse Spin Hall emitters exploiting Spin Reorientation Transition of an anisotropic CoFeB layer

We demonstrate an efficient and simple modulation of the polarization in Inverse Spin Hall Effect spintronic Terahertz Emitters (ISHE STE), by rapid switching of the magnetization using a high-frequency magnetic field, enhanced by field induced Spin Reorientation Transition (SRT). The instability of the magnetic layer at this transition allows for a higher sensitivity of the magnetization and for an efficient rotation of the polarization at frequencies up to 10MHz at lower RF powers. The observed modulation bandwidth seems to be merely limited by instrumental limitations. The SRT mechanism is expected to allow ultrafast modulation of spintronic THz emitters well beyond 100MHz.