Ultrafast photo-magnetic recording in transparent medium (1609.05223v1)

Abstract: Finding a conceptually new way to control the magnetic state of media with the lowest possible production of heat and simultaneously at the fastest possible time-scale is a new challenge in fundamental magnetism [1-4] as well as an increasingly important issue in modern information technology [5]. Recent results demonstrate that exclusively in metals it is possible to switch magnetization between metastable states by femtosecond circularly polarized laser pulses [6-8]. However, despite the record breaking speed of the switching, the mechanisms in these materials are directly related to strong optical absorption and laser-induced heating close to the Curie temperature [9-12]. Here we report about ultrafast all-optical photo-magnetic recording in transparent dielectrics. In ferrimagnetic garnet film a single linearly polarized femtosecond laser pulse breaks the degeneracy between metastable magnetic states and promotes switching of spins between them. Changing the polarization of the laser pulse we deterministically steer the net magnetization in the garnet, write "0" and "1" magnetic bits at will. This mechanism operates at room temperature and allows ever fastest write-read magnetic recording event (< 20 ps) accompanied by unprecedentedly low heat load (< 6 J/cm3).

• The paper introduces a novel all-optical switching method via linearly polarized femtosecond laser pulses in Co-doped YIG.
• It employs time-resolved femtosecond single-shot imaging to capture 20 ps magnetization dynamics with minimal energy dissipation (6 J/cm²).
• The results pave the way for low-thermal-budget magnetic memory devices, offering potential improvements for MRAM and related technologies.

Ultrafast Photo-Magnetic Recording in Transparent Medium

The presented paper explores a cutting-edge method of ultrafast photo-magnetic recording using transparent dielectrics, specifically focusing on Co-doped yttrium iron garnet (YIG:Co). The paper documents a novel, efficient approach for controlling the magnetic state of a medium utilizing linearly polarized femtosecond laser pulses, marking a significant departure from traditional thermally-driven magnetic switching in metallic systems. This research addresses the pressing need for minimizing heat dissipation in high-speed data recording, a critical factor in advancing modern information technologies.

Mechanism and Methodology:

The experiment exploits the photo-magnetic characteristics of a YIG:Co film, an optically transparent ferrimagnetic dielectric with antiferromagnetically coupled spin sublattices of Fe ions, to achieve all-optical switching. The mechanism involves the use of single laser pulses to induce magnetic state transitions while avoiding significant thermal effects. The polarization direction of the laser pulse dictates the resultant switching, enabling deterministic manipulation of the magnetization direction within the garnet substrate.

The research employed time-resolved femtosecond single-shot imaging to monitor the ultrafast dynamics of magnetization switching. This methodology facilitated the evaluation of switching speed and the energy efficiency of the process by capturing magneto-optical images at various time intervals post-laser irradiation.

Key Numerical Results:

The findings reveal that magnetic recording at room temperature can be achieved within 20 ps, with an energy dissipation as low as 6 J/cm². This is in stark contrast to the energy demands of other technologies such as all-optical switching in metals, hard disk drives, and even advanced memory technologies like STT-RAM, where energy requirements are typically orders of magnitude higher. Notably, the minimal heat load accompanying this process is attributed to the low optical absorption of the transparent medium, which circumvents the necessity of heating the material near its Curie temperature.

Implications and Future Prospects:

The implications of this paper are significant in the context of developing new materials and methods for opto-magnetic recording. The low thermal budget and rapid switching capability suggest potential for implementing this technology as a standalone system or as an enhancement to existing methods like Heat Assisted Magnetic Recording (HAMR).

Further investigations could explore the integration of electric field control in combination with this optical approach, potentially resulting in an exceptionally fast and energy-efficient Magnetic Random Access Memory (MRAM). Such advancements would leverage the tunable magnetic anisotropy in garnet films, ultimately fostering innovative, sustainable solutions for high-speed data storage applications.

In conclusion, the paper elucidates a promising avenue for ultrafast, energy-efficient magnetic recording technologies by harnessing the intrinsic properties of Co-doped garnets. The effort to balance speed, energy efficiency, and material integrity embodies a crucial advancement toward overcoming the current limitations in data storage technology.