Spatially periodic magnetic structure produced by femtosecond laser-induced crystallization of amorphous Co2MnSi thin film

초록

Femtosecond laser-induced grating was used to form a spatially periodic magnetic structure by selectively crystallizing a paramagnetic Co2MnSi amorphous film which crystallizes into a ferromagnetic phase. The periodic structure was obtained by two-beam interference of laser pulses. The femtosecond laser system used was a regeneratively amplified Ti:Sapphire laser with 800-nm wavelength, 130-fs pulse duration, 1.0-mJ maximum pulse energy, and 1-kHz repetition rate. Transmission electron microscopy showed regularly spaced alternating lines with a periodicity of 2 ㎛. The crystalline region was composed of ~100 nm sized crystals. The main crystalline phase was fcc-Co intermixed with β-Mn. Figure 1 shows the magnetic force microscopy of the sample which reveals the periodic magnetic domains. The periodicity was 1 ㎛ due to the partial crystallization of the low fluence regions. The periodicity of the modulated structure can be reduced to a submicrometer scale and a two-dimensional structure can be also formed by appropriately adjusting the interference pattern and the beam intensity so that the technique could be utilized for a permanent magnetic ID