Nanoscale Confinement of All-Optical Magnetic Switching in TbFeCo - Competition with Nanoscale Heterogeneity

Abstract

Single femtosecond optical laser pulses, of sufficient intensity, are demonstrated to reverse magnetization in a process known as all-optical switching. Gold two-wire antennas are placed on the all-optical switching film TbFeCo. These structures are resonant with the optical field, and they create a field enhancement in the near-field which confines the area where optical switching can occur. The magnetic switching that occurs around and below the antenna is imaged using resonant X-ray holography and magnetic circular dichroism. The results not only show the feasibility of controllable switching with antenna assistance but also demonstrate the highly inhomogeneous nature of the switching process, which is attributed to the process depending on the material's heterogeneity.

Conditions for thermally induced all-optical switching in ferrimagnetic alloys: Modeling of TbCo

“…This shows that this value, although somewhat arbitrary, is close to the real one for ultrathin metallic films. In the present work the simulations always start at room temperature T room = 300 K. Figure 2 presents an example of simulated magnetization dynamics, in this case for Tb 32 Co 68 and laser pulse duration τ p = 50 fs. Note that this composition does not have a magnetization compensation point.…”

“…At the same time, both TbFe and TbCo present larger anisotropy than GdFe, and thus potentially are more relevant for applications. Recently nanoscale magnetic recording with AOS technology using near-field optics has been reported on TbFeCo thin films [32]. Most of the experimental studies on TbCo have been subject to switching through the use of circularly polarized laser pulses [7,17,20] that confirmed the occurrence of AOS in TbCo, but mainly the inverse-Faraday effect has been speculated as the mechanism.…”

Electric current induced ultrafast demagnetization

“…Laser irradiation of magnetic metals can launch precessional modes at frequencies ranging from a few to hundreds of GHz 2,3 , drive ultrafast magnetic phase transitions 4 , and generate enormous pure spin-currents [5][6][7][8][9][10][11] . Optical irradiation of ferrimagnetic systems such as GdFeCo and TbFeCo can result in an ultrafast reversal of the direction of magnetization [12][13][14] . Several recent studies have observed the response of magnetic metals to free-space THz radiation 15,16 .…”

Photon Beam Transport and Scientific Instruments at the European XFEL

“…Such experiments open up a route to follow the dynamics in complex systems on their relevant length and time scales. The SCS instrument further implements Coherent Diffraction Imaging (CDI) techniques, i.e., X-ray holography [90,91]. A time series of reconstructed CDI images can elucidate excited state dynamics in real space.…”