Colloquium
Department of Physics, NCU
Visualizing hydrogen diffusion in Co25Pd75 alloy film through the magneto-optical Kerr effect
Speaker
Prof. Lin, Wen-Chin 林文欽教授
Department of Physics, NTNU
臺灣師範大學 物理學系
Date 2019.03.19(Tue)
Time 14:00-16:00
Place S4-625
Abstract
Hydrogen diffusion in Co25Pd75 alloy film was real-time monitored using a magneto-optical Kerr microscope. Hydrogen absorption increased the remanence (Mr) to saturation (Ms) ratio in the magnetic hysteresis loop of Co25Pd75 film from 20% to 100% when the hydrogen/metal atomic ratio increased from 0% to 5%. The spatially resolved magneto-optical contrasted images thus provided a noninvasive method of monitoring hydrogen movement in a magnetic thin film. Hydrogen absorption and diffusion followed Fick’s diffusion law, and a diffusion coefficient of 4 ± 2 × 10-12 m2/s was obtained by fitting the spatial distribution of hydrogen content. The diffusion velocity of the 2%, 3%, and 4% hydrogen concentration fronts reached 30 ± 15 nm/s in the uniform film area and increased to 50 ± 20 nm/s near a defect site. During hydrogen desorption, the lateral diffusion speed of hydrogen content within the alloy film was measured at 30 ± 15 nm/s. These results demonstrated that hydrogen diffusion in nontransparent Pd-rich magnetic alloy thin films could be monitored, with possible applications in hydrogen-sensing and -storage technology.