Xu Haitian, Hajisalem Ghazal, Steeves Geoffrey M, Gordon Reuven, Choi Byoung C
Department of Physics and Astronomy, University of Victoria, Victoria V8P 5C2, Canada.
Department of Electrical and Computer Engineering, University of Victoria, Victoria V8P 5C2, Canada.
Sci Rep. 2015 Oct 30;5:15933. doi: 10.1038/srep15933.
Ultrafast laser-induced magnetization dynamics in ferromagnetic thin films were measured using a femtosecond Ti:sapphire laser in a pump-probe magneto-optic Kerr effect setup. The effect of plasmon resonance on the transient magnetization was investigated by drop-coating the ferromagnetic films with dimensionally-tuned gold nanorods supporting longitudinal surface plasmon resonance near the central wavelength of the pump laser. With ~4% nanorod areal coverage, we observe a >50% increase in demagnetization signal in nanorod-coated samples at pump fluences on the order of 0.1 mJ/cm(2) due to surface plasmon-mediated localized electric-field enhancement, an effect which becomes more significant at higher laser fluences. We were able to qualitatively reproduce the experimental observations using finite-difference time-domain simulations and mean-field theory. This dramatic enhancement of ultrafast laser-induced demagnetization points to possible applications of nanorod-coated thin films in heat-assisted magnetic recording.
在泵浦-探测磁光克尔效应装置中，使用飞秒钛宝石激光器测量了铁磁薄膜中超快激光诱导的磁化动力学。通过用尺寸调谐的金纳米棒对铁磁薄膜进行旋涂，研究了等离子体共振对瞬态磁化的影响，这些金纳米棒在泵浦激光的中心波长附近支持纵向表面等离子体共振。在纳米棒面积覆盖率约为4%的情况下，由于表面等离子体介导的局部电场增强，我们观察到在泵浦通量约为0.1 mJ/cm²时，纳米棒涂层样品的退磁信号增加了50%以上，这种效应在更高的激光通量下变得更加显著。我们能够使用时域有限差分模拟和平均场理论定性地重现实验观察结果。超快激光诱导退磁的这种显著增强表明纳米棒涂层薄膜在热辅助磁记录中可能具有应用前景。
