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| 連携融合セミナーNo.2 |
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基礎工学研究科 連携融合事業セミナー No.2
日時：１月７日（木）13:30-
場所：基礎工学部 G508講義室
(基礎工G棟です。D棟と2階渡り廊下で繋がった東の建物です)
講師：Dr.Toshio Miyamachi
所属：Karlsruher Institut für Technologie (KIT), Physikalisches Institut,
Germany
題目：Probing magnetic stability of single atoms and clusters by scanning
tunneling microscope
The magnetic stability of bits in a hard disk relies on the energetic barrier
to reverse the magnetization, which is governed by magnetic anisotropy
energy (MAE). Recent x-ray magnetic circular dichroism study has revealed
a giant MAE of Co atoms on Pt(111) of 9.3 meV [1], raising hope for realizing
ultimate miniaturization of bits. This technique, however, cannot extract
information about the magnetization dynamics, which also plays an important
role for the stability of bits. Here we demonstrate that inelastic tunneling
spectroscopy using scanning tunneling microscope (STM) can investigate
the lifetimes of magnetically excited states in addition to MAE [2]. By
virtue of atomic manipulation capabilities of the STM, these properties
are determined with the highest precision for single atoms, dimers and
trimers of Fe and Co on Pt(111). The obtained values of MAE are found to
strongly depend on the cluster size and correspond well to the ones by
XMCD. The results are also compared to relativistic ab initio calculations
of the MAE of fully relaxed structures. The estimated short lifetimes of
the order of femtoseconds are explained from efficient electron-electron
scattering processes induced by the strong hybridization of the impurity
state and the substrate.
References:
[1] P. Gambardella et al., Science 300, 1130 (2003)
[2] T. Balashov et al., PRL 102, 257203 (2009)
問い合わせ先 大阪大学基礎工学研究科連携融合事業 菅滋正(6493)
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