Abstract
Using an ultrafast laser pulse as a substitution of continuous-wave laser to excite a magnetic film leads to high spin temperature and fast demagnetization, beneficial to the rapid and efficient photo-assisted magnetization (M) reversal. Here, ultrafast laser induced M reversal in perpendicular magnetic anisotropy L10 FePt films with different chemical ordering parameter (from S<0.6 to S>0.9) was investigated using magneto-optical Kerr effect (MOKE). It was found that the coercive field (Hc) without laser excitation increases from ∼0.8 to ∼4 kOe with increasing S, but Hc becomes smaller for enhanced laser fluence (F) and reaches an analogous small value of ∼0.2 kOe for F>12 mJ cm-2. Despite such a significant softening in films with high S, the laser induced M reversal rate is slightly less than 1 even for the applied field (H) much larger than 0.2 kOe. This reveals a small portion of spins are photo inactively pinned, as confirmed by magnetic force microscopy measurements. Such pinning sites may be reduced with improved chemical order and morphology. We also found an approximately inverse linear relation between the H and the corresponding threshold F to induce the M reversal in the film of high S, which can be described by an ultrafast thermal activated spin flip model.
Highlights
The increasing demand for higher density, faster speed, and more stable magnetic recording intrigues exploration of effective methods to reverse the magnetization (M) in high perpendicular magnetic anisotropy (PMA) materials.1–3 As one of the leading candidates for the next-generation recording materials, L10FePt with high PMA (>4×107 erg cm-3) has received extensive research
Using an ultrafast laser pulse as a substitution of continuous-wave laser to excite a magnetic film leads to high spin temperature and fast demagnetization, beneficial to the rapid and efficient photo-assisted magnetization (M) reversal
We found an approximately inverse linear relation between the H and the corresponding threshold F to induce the M reversal in the film of high S, which can be described by an ultrafast thermal activated spin flip model
Summary
The increasing demand for higher density, faster speed, and more stable magnetic recording intrigues exploration of effective methods to reverse the magnetization (M) in high perpendicular magnetic anisotropy (PMA) materials. As one of the leading candidates for the next-generation recording materials, L10FePt with high PMA (>4×107 erg cm-3) has received extensive research. The increasing demand for higher density, faster speed, and more stable magnetic recording intrigues exploration of effective methods to reverse the magnetization (M) in high perpendicular magnetic anisotropy (PMA) materials.. As one of the leading candidates for the next-generation recording materials, L10FePt with high PMA (>4×107 erg cm-3) has received extensive research. The high coercivity (Hc) of L10FePt is a byproduct because a large applied magnetic field (H) is required to control its spin orientation. To reduce H in the M reversal process, the heat assisted magnetic recording technology using continuous-wave (CW) laser has been implemented.. Employing a short laser pulse in this technology demonstrates superiority in terms of reduced thermal diffusion and spot size, it is favorable for higher recording density. To reduce H in the M reversal process, the heat assisted magnetic recording technology using continuous-wave (CW) laser has been implemented. employing a short laser pulse in this technology demonstrates superiority in terms of reduced thermal diffusion and spot size, it is favorable for higher recording density.
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