Photon Factory Activity Report 2004 #22 Part B (2005)
Materials Science

NE1B/2004G008

Magnetization and Magnetic Circular Soft x-ray Dichroismof Electrodeposited Nickel Covered with GoldKoh-ichi MARUYAMA1, Etsuo ARAKAWA2, Ko-ichi HIRAKI3, Hirokazu WATANABE1,4514Hitoshi YAMAGUCHI , Hiroo NUMATA , Toshihiko YOKOYAMA , Akiyuki MATSUSHITA ,672
8Koichi Mori , Tsuneharu KOIDE , Kazumichi NAMIKAWA , Osamu NITTONO
1IMS, Okazaki, Aichi 444-8585, Japan, 2Tokyo-Gakugei Univ., Koganei, Tokyo 186-8501, Japan,
3Universite Joseph Fourier Grenoble I, Saint-Martin d'Heres, France, 4NIMS, Tsukuba, Iraraki 3050047, Japan, 5TIT, Meguro, Tokyo 152-8522, Japan, 6IPU, Inashiki, Ibaraki 300-0394, Japan, 7KEKPF, Tsukuba, Ibaraki 305-0801, Japan, 8Fukushima Univ., Fukushima, Fukushima 960-1296, Japan
We have studied nanostructure and its magnetic
properties of the electrodeposited(ED) transition-metal . It
is interesting that the properties link to theelectrochemical behaviour due to the “electrolyticcatalysis” at the initial stage of electrodeposition. We
found the abnormal increase of magnetization for thenickel film electrodeposited on carbon substrate. Themagnetization was measured by SQUID, and however it
might be difficult to separate strictly the components ofthe film and the substrate. On the other hands, MCXD is avery useful probe only for the film magnetization,
because of the element-resolved detection. In addition, it
is very sensitive to the surface oxide layer. We reported
that XAS of ED nickel film was separated into those ofnickel and nickel oxide. The ratio of their parts could becalculated, and lead to the meaningful MCXD intensity,spin- and orbital- magnetic moments. However it wasdifficult to determine the MCXD for the deposits thinnerthan 3 monolayer(ML) in this manner. We havechallenged magnetization detection for the thinnerdeposits covered with gold by the electroless deposition.
Figure 1 shows magnetization versus deposit thickness
for gold-coated and bare nickel. Magnetization saturated
in the field more than 4 tesla. Error bars of data points
denote the obscured ranges due to the magnetic
components of substrate. The magnetization of goldcoated nickel deposits increased with a decrease in thethickness less than 5ML, and reached to twentieth times
as large as that of the bulk nickel. The bare nickel
exhibited similarly to these deposits, except for 0.5MLdeposit, which may be the magnetization reduction due tothe surface oxidation in air after the electrodeposition.
Figure 2 shows XAS and MCXD of Ni L3,2 edge forseveral gold-coated ED nickel(30nm) deposits and theelectron-beam evaporated (BE) gold(2nm)/nickel(15nm)
films on amorphous carbon, used as a reference of purenickel. For Au 1nm sample, the intensity of L3 peaksignificantly increased, and that of the region between L3and L2, and the energy region higher than L2 edge wasdecreased, which is the similar to XAS of the surface
oxidation of bare nickel deposits, and the reduction ofMCXD obtained due to the antiferromagnetic order ofnickel element. For Au 5nm sample, only the enhanced
increase of L3 peak appeared, which may be the change inthe electron hole due to the alloy formation, Au-Ni. Non-164

Users' Report

Fig.1 Magnetization of gold-coated and bare ED nickel on
carbon substrate. Ferromagnetic component saturates
within about 1 tesla field, and super paramagneticcomponents, 4 tesla. The total magnetization means theaddition of both components.

Fig. 2 XAS and MCXD of the gold-coated ED and BE
nickel films. BE one is a reference as non-oxide nickel. XAS
contains Ni, Ni-oxide, and Ni-Au phases for ED samples.

reduction of MCXD intensity of this sample is explainedby the ferromagnetic order of Ni element in alloy.
However it was difficult to determine the ratio of thesurface oxidation, for Au 3nm sample, and for the thinner
nickel deposits covered with gold, in spite of the simple
coating technique.
We are trying to prepare the sample by the othertechniques of gold coating, and to detect the MCXD ofthe thinner nickel deposits.
* maruko@ims.ac.jp