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碩博班專題討論(Colloquium)

Control of magnetism by hydrogen diffusion

演講者 : 林文欽 教授 (師大物理系)
演講時間 : 2021 / 11 / 12 14:10
理學教學新大樓物理系1F 36102教室
理學教學新大樓物理系1F 36102教室 位於....
After catalyzed dissociation and under suitable temperature, hydrogen atoms can easily diffuse in solid materials, because of the very small atomic size (only around 0.1 nm in diameter). The hydrogen atoms can diffuse in the interstitial space between the solid atoms and gradually reach a saturated concentration. In the hydride materials, because of the charge transferring between hydrogen and host-atoms, the presence of hydrogen usually leads to drastic changes in the optical, electrical and magnetic properties. Our previous studies have demonstrated that reversible hydrogenation under suitable hydrogen gas pressure provides an effective method for the manipulation of magnetism in Co-Pd and Fe-Pd alloys.

Lately we focused on the magnetic property of FexPd1-x alloy films in this study, because of the much longer H-desorption time. The survey of FexPd1-x alloy thin films with various Fe concentration, thickness and crystalline structure was conducted with the characterization by magneto-optical Kerr microscopy. The hysteresis loops were measured either in a vacuum or under 1 bar hydrogen gas pressure for comparison. Not only the coercivity but also the magnetic easy axis and magnetic domain structure were changed by hydrogenation. In addition, the desorption time of hydrogen from the FexPd1-x alloy films was also confirmed, so that we can perform MR-measurement with H-content. These results are important for us to figure out the correlation between hydrogen and magnetization in FexPd1-x alloy thin films.