32nd Magnetic Materials Center Seminar
December 4, 2006, 10:30
7th floor seminar room, Sengen
Microstructure and Magnetic properties of FePt-ZrO2 granular films
H. Takeshita
L10-FePt thin film has received much attention for the high density magnetic recording media, because this alloys has very large magnetocrystalline anisotropy energy(Ku).Nonmagnetism phase surrounds FePt grains in L10-FePt nano-granular films.And control FePt grain size.I chose nonmagnetism phase as ZrO2.ZrO2's diffusion speed is slower than SiO2. So, it can lower FePt grain size.
In this seminar, I will present the reduction of FePt grain size in ZrO2 nonmagnetism phase, and crystal structure of ZrO2.

"Fermi level tuning" in Heusler alloys by fourth elements
T. Nakatani
We have investugated Co2FeAlxSi1-x series. The values of spin polarization for Co2FeSi and Co2FeAl were 0.57 and 0.56, respectively(Co2FeAl by Karthik), whereas, that of Co2FeAl0.5Si0.5, which is the intermidiate compound, showed P=0.60, i.e. we could impove spin polarization by alloying. The reason is possibly due to the change of the position of the Fermi level in the minority gap. Recently C. Felser group and Dr. Gercsi showed calculations to inditate this.
And also, Co2Mn0.5Fe0.5Si was predicted to have the same tendency by C. Felser G, I measured the spin polarization, which showed somehow high spin polarization.
In this semiar, I will show the guidline to get high spin polarization.

Structure and magnetic properties of Co ferrite thin film
Y. K. Takahashi
To obtain high performance in the spintronics devices, a highly spin polarized current source is really desired. A half metal ferromagnet is well known to show the highly spin polarization. Especially, Co-based Heusler alloys have much attention, because it is predicted to have 100% spin polarization and the Curie temperature is enough high for the practical application. The spin filtering device can generate the highly spin polarized current, too.
CoFe2O4 is one of the candidates for the barrier in the spin filtering device, because it has high Curie temperature. I made CoFe2O4 thin film by the radical oxidation method at various temperatures and check the structure and the magnetic properties. In this talk, I will present the preliminary results on the fabrication of CoFe2O4.