Magnetization orientation in materials can be manipulated at extremely short time scales using intense laser pulses. Traditionally, this manipulation is thermally induced, where absorbed laser energy rapidly heats up the material, causing a perturbation of the magnetic order. However, scientists from the Max Born Institute (MBI) and an international team of researchers have introduced a non-thermal method to generate significant magnetization changes. By exposing a ferrimagnetic iron-gadolinium alloy to circularly polarized extreme ultraviolet (XUV) radiation, they observed a strong magnetic response depending on the handedness of the incoming light burst.
The conventional understanding of magnetization manipulation involves the absorption of energy by the material due to the intense laser pulse. This energy excites electrons, leading to changes in electron spin and orbital moments, ultimately affecting magnetization. While this process results in fascinating phenomena like ultrafast demagnetization and laser-induced magnetization switching, it also generates substantial heat in the material, limiting its technological use in applications requiring fast repetition rates.
The research team, led by scientists from MBI, explored a non-thermal approach to magnetism manipulation using a phenomenon called the inverse Faraday effect (IFE). Unlike traditional methods relying on electronic heating from light absorption, the IFE involves a coherent interaction between the light’s polarization and the electronic spins. This novel technique bypasses the electronic heating bottleneck, offering a new pathway for efficient magnetization control.
Most ferro- and antiferromagnetic materials exhibit metallic and absorptive properties that suppress non-thermal effects. To overcome this limitation, the researchers utilized circularly polarized femtosecond XUV radiation from the free-electron laser FERMI. The high photon energy of the XUV radiation enables resonant excitation of core-level electrons in the ferrimagnetic iron-gadolinium alloy, promoting large opto-magnetic effects.
The experimental results demonstrated a substantial IFE-induced magnetization in the FeGd alloy, reaching 20-30% of the ground-state magnetization. This significant magnetization manipulation, measured by the difference in demagnetization for opposite helicities of the circularly polarized XUV pulses, highlights the effectiveness of the non-thermal approach. Moreover, theoretical calculations and simulations support the observed effects, confirming the role of the IFE in generating magnetization changes.
The development of a non-thermal method for generating large magnetization changes on ultrafast time scales holds promise for various fields, including ultrafast magnetism, spintronics, and coherent magnetization control. By harnessing the unique properties of extreme ultraviolet radiation and the inverse Faraday effect, researchers can explore new avenues for manipulating magnetism without the constraints of thermal effects.
The study by the Max Born Institute and collaborators sheds light on a novel approach to controlling magnetization using non-thermal mechanisms. By leveraging circularly polarized XUV radiation and the inverse Faraday effect, researchers have demonstrated an efficient and effective method for generating large magnetization changes in materials. These findings pave the way for future advancements in ultrafast magnetism research and the development of innovative spintronic devices.
Leave a Reply