Ultrafast Spin Dynamics

Ultrafast spin dynamics is one of the key aspects in the realization of ultrafast spintronic devices. Moreover, it has attracted much attention due to important fundamental spin phenomena existing on nano-, pico-, and femtosecond timescales. The most important interaction of magnetism is, of course, an exchange interaction. However, in practice, spin generally exists interacting with a lattice and an electron in the form of solid. Therefore, a fundamental understanding of ultrafast spin dynamics is involved in various physical phenomena, such as spin-orbit interactions and optomagnetism. In this article, recent trends in ultrafast spin dynamics research are discussed. Ultrafast spin dynamics, which started with the observation of ultrafast demagnetization/remagnetization triggered by femtosecond laser pulses, has been intensively investigated so far. The magnetooptical Kerr effect and X-ray magnetic circular dichroism techniques are introduced as two of the main experimental techniques for exploring ultrafast spin dynamics. THz emission and ultrafast magnetic cooling phenomena are briefly introduced as examples of recent topics in the field of ultrafast spin dynamics.