77th Magnetic Materials Center Seminar
June 6, 2008, 9:00-
7th floor small seminar room, Sengen
53% TMR using Co75Fe25 as ferromagnetic electrodes and Al-Oxide barriers on a-SiO2 substrates.
S. V. Karthik
We fabricated magnetic tunnel junctions (MTJs) on amorphous SiO2 substrates using Co75Fe25 as ferromagnetic electrodes, Al-Oxide as barrier, IrMn for antiferromagnetic exchange coupling and Ru as capping layer. The sputtering parameters such as power, Ar pressure, temperature were optimized for Co75Fe25 electrodes. The O2/Ar ratio, oxidation time and RF power (Radical oxidation) were optimized for obtaining Al-Oxide barrier without defects, pinholes and good chemical stoichiometry (Al2O3). Using the best optimized conditions, we were able to consistently obtain a TMR of 50-53% which corresponds to a spin polarization of 0.46 using Jullier's model. This TMR value is quite consistent with the experimental results by other research groups using Plasma oxidation. Our results using radical oxidation to obtain high TMR is unique as other scientific reports suggest a lower TMR (<40%) owing to the formation of Fe2O3 at the ferromagnet/barrier interface.

Microstructure and magnetic properties of the NdFeB Films sputtered on Cr buffer layer
K. Suresh
We have investigated micro-structure and magnetic properties of the hard magnetic Nd2Fe14B thin films sputtered on a Cr buffer layer on single crystalline MgO(100) and MgO(111) and amorphous oxidized Si (a-SiO2) substrates. The films were deposited at 650oC. Structural and magnetic studies reveal that NdFeB films deposited on MgO(100) and Mg(111) substrates were highly anisotropic and exhibit excellent combination hard magnetic properties where as films deposited on a-SiO2 exhibit poor magnetic property. In this presentation I will present micro-structure and magnetic properties of the NdFeB films sputtered on Cr buffer layer on MgO(100), MgO(111) and a-SiO2 substrates.

Optimization of growth condition of SmCo5 thin film on MgO(110) substrate
N. Hase
It is well-known that Cu additon to Sm-Co system magnets produces the Hc enhancement. But, the role of Cu for the Hc enhancement is still unclear. Then, the objective of this research is makng clear this problem. In this talk, I'll show the optimized growth condition of SmCo5 thin film.