51st Magnetic Materials Center Seminar
July 20, 2007, 9:00
7th floor seminar room, Sengen
Magnetic properties and microstructure of NdFeB/Ta thin film
H. Takeshita
Nd2Fe14B-based thin films are candidate materials for micro-mechanical devices. In order to improve the performance of Nd2Fe14B-based thin films, some technicalproblemes need to be overcome. The one of problem is that the magnets need to be highly anisotropic in order that the increased remanence exhibits in the easy direction of magnetization. This means the Nd2Fe14B must be aligned with the c-axis pointing in a particular direction. M.Uehara reported that the perpendicular anisotropy and hard magnetic prpperties are enhanced in NdFeB/Ta thin films. In this presentation, I would like to discuss the microstructure and magnetic properties of NdFeB/Ta thin films.

Coercivity generation of surface Nd2Fe14B grains and fcc phase formation mechanism at Nd/Nd2Fe14B interface in Nd sputtered NdFeB sintered magnets.
T. Fukagawa
In the previous presentation, the relationship between coercivity of Nd2Fe14B grains and the microstructure of Nd-rich layer adjacent to them has been studied by observing coercivity of surface grains of thin plate Nd-Fe-B sintered magnets with surfaces covered by sputter-deposited Nd fim. Then it has been clarified that formation of an fcc phase is necessary in order to generate the coercivity in Nd2Fe14B grains at the interface.
In this presentation, I want to discuss about formation mechanism of the fcc phase with comparing Nd compounds between near the interface with Nd2Fe14B and in the inner area apart from the interface in Nd film in the thin plate Nd-Fe-B sintered magnets with surfaces covered by sputter-deposited Nd film.

Microstructure, magnetic and transport properties of Co-ferrite thin film.
Y.K. Takahashi
Development of of the highly spin polarized current source is important issuse in the spintronics area. Spin filtering device with ferromagnetic insulator such as Co-ferrite, Ni-ferrite is expected to show the spin filitering effect at RT. Although the spin filtering effect was ovserved at low temperature, that at RT is still very small. The purpose of this work is to obtain the spin filtering effect at RT.
Co ferrite thin film was fabricated by the radical oxidation of CoFe2 film. HREM images and magnetic properties show that the CoFe2 film changes to Co ferrite perfectly at higher than 350C of substrate temperature. However, the transport properties show the metallic nature. In the presentation, I would like to discuss the reason why our Co ferrite does not show the insulator nature.