Laser-Induced Magnetization: A Revolutionary Approach in Material Science

A powerful laser pulse, when directed at an iron alloy, momentarily melts the targeted area, creating a small magnetic zone. This finding is credited to HZDR / Sander Münster.

A collaborative study has uncovered that brief, intense laser pulses can induce magnetization in iron alloys. This advancement has significant implications for magnetic sensor technology, data storage, and the field of spintronics.

Traditionally, magnetizing an iron nail involves rubbing it with a bar magnet. However, researchers from the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), in partnership with Laserinstitut Hochschule Mittweida (LHM), have developed an unconventional method: utilizing ultrashort laser pulses on certain iron alloys to induce magnetization. Their research extends to different material classes, potentially widening the scope of applications. These findings are published in the journal Advanced Functional Materials.

Innovations in Magnetization Techniques

This surprising discovery dates back to 2018. The HZDR team found that when an iron-aluminum alloy layer was exposed to ultrashort laser pulses, the non-magnetic material transformed into a magnetic one. The laser pulses rearrange the atomic structure, causing iron atoms to cluster more closely and form a magnet. The researchers could then reverse the magnetization with weaker laser pulses, enabling them to create and erase small magnetic areas on a surface.

The initial experiment raised several questions. Dr. Rantej Bali of HZDR sought to determine whether this effect was exclusive to the iron-aluminum alloy or applicable to other materials. Collaborating with Dr. Theo Pflug of LHM and colleagues from the University of Zaragoza, they expanded their research.

Studying Magnetization with Laser Pulses

Their focus shifted to an iron-vanadium alloy, which, unlike the structured iron-aluminum alloy, has a more disordered, amorphous atomic arrangement. They utilized the pump-probe method to monitor the effects of laser irradiation.

“We magnetize the alloy with a strong laser pulse and simultaneously reflect a weaker pulse off the material surface,” explains Theo Pflug. The reflected pulse analysis helps to ascertain the material’s physical attributes. This process is repeated, extending the interval between the initial and subsequent pulses, creating a sequential reflection data set that illustrates the laser-triggered processes.

Quick Melting and Magnetic Formation

The research revealed that the iron-vanadium alloy, despite its differing atomic structure, could be magnetized through laser exposure. “In both alloys, the laser pulse briefly melts the material at the point of irradiation, erasing the previous structure and forming a small magnetic area,” clarifies Rantej Bali.

This indicates that such magnetic phenomena can occur in various atomic structures.

The team is also analyzing the timing of these processes. “We now understand the timescale of these events,” adds Theo Pflug. Initially, the laser pulse energizes the electrons, which, within picoseconds, transfer energy to the atomic nuclei. This energy transfer leads to the formation of a magnetic structure, which is then stabilized by rapid cooling. Future experiments will focus on observing the atomic rearrangement during magnetization using intense X-rays.

Potential Applications in Sight

Although still in developmental stages, this research suggests potential applications. For instance, using lasers to place tiny magnets on a chip surface could benefit magnetic sensor manufacturing in vehicles and magnetic data storage.

This phenomenon might also play a role in spintronics, where magnetic signals could replace electrons in transistors for digital computing, paving the way for future computer technology.

Reference: “Laser-Induced Positional and Chemical Lattice Reordering Generating Ferromagnetism” by Theo Pflug, Javier Pablo-Navarro, Md. Shabad Anwar, Markus Olbrich, César Magén, Manuel Ricardo Ibarra, Kay Potzger, Jürgen Faßbender, Jürgen Lindner, Alexander Horn and Rantej Bali, 21 November 2023, Advanced Functional Materials.
DOI: 10.1002/adfm.202311951

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