78th Magnetic Materials Center Seminar
June 11, 2008, 9:00-
7th floor small seminar room, Sengen

attempt to fabricate CPP-GMR spin valves using Co40Fe40B20 alloy.
C. Y. You
In a current-perpendicular-to-plane (CPP) geometry, giant magnetoresistance (GMR) effect is significantly weakened by the large gparasitich resistance from non-active part of the spin-valve structure, such as antiferromagnetic layer. One of ways to solve this problem is an usage of high resistivity ferromagnetic materials. CoFeB alloy has high resistivity and low anisotropy. Moreover, it was reported that amorphous CoFeB possesses higher spin polarization than CoFe. Due to amorphous structure, CoFeB has also very good structure compatibility. In this seminar, I will present some preliminary results of attempt to fabricate CPP-GMR spin valves using Co40Fe40B20 alloy.

3DAP analysis of high-doped (Ga,Mn)As
M. Kodzuka
3DAP analysis of(Ga,Mn)As has been performed to get the information of Mn distribution in (Ga,Mn)As. In my previous presentation, it was shown that low-doped (Ga,Mn)As, Ga0.95Mn0.05As has uniform distribution of Mn. It is known that the magnetic properties of (Ga,Mn)As depend on Mn concentration. So, I will report the 3DAP analysis results of high-doped (Ga,Mn)As, Ga0.80Mn0.20As in this presentation.

TEM analysis of Co2MnSi/MgO/Co2MnSi magnetic tunneling junctions
T. Nakatani
Magnetic tunneling junctions with well-ordered Heusler alloys can show high tunneling magnetoresistance (TMR) values, however, a consensus on the relationship between the ordering and the spin polarization has not been obtained. The samples composed of CMS/MgO/CMS (CMS=Co2MnSi) epitaxial structure, which were provided by Hokkaido univ, The both CMS electrodes were post-annealed after the each deposition, where 600C for lower CMS and 400C or 550C for upper CMS, and they show deferent TMR values. A nano-beam diffraction analysis has revealed the deferent degrees of ordered in the upper CMS layers, which seems to result in the deference TMR properties. Moreover in the seminar the structures will be discussed relating with the transport properties. In addition nuclear magnetic resonance experiment will be mentioned as my near-future research plan, which is useful method to study ordered structure.