50th Magnetic Materials Center Seminar
July 6, 2007, 9:00
7th floor seminar room, Sengen
Exchange Bias and Factors Effecting it in Co2(CrFe)Si GMR films
H.S. Goripati
As Exchange bias is an important factor in achieving high MR, I made an attempt to tailor the required exchage bias for making CPP GMR junctions. Though exchange bias dpends on many factors, I will make an attempt to present few of them including the discussion on difficulties in achieving exchange. In the end a strong exchange bais of over 500 Oe is achieved on silica substrate with copper under layer deposited at room temperature.

Spin polarization in (Co,Fe)2CrGa Hesuler alloys
T. Nakatani
As a method to overcome the reduction of the spin polarization of Heusler alloys from the half-metallicity, addition of a fourth elemnts may be effective. I attempted a partial substitution of cobalt site with iron in Co2CrGa with an intention to increase the up-spin electron state at the Fermi level.
Co2CrGa and Co1.9Fe0.1CrGa were made by arc melting. Co2CrGa showed a spin polarization of P=0.58-0.60, as well as other Heuler alloys wihch we have ever investigated. On the other hand Co1.9Fe0.1CrGa showed P=0.67, which is the highest value among Heusler alloys ever measured by the PCAR method. This result indicates an apparent efficiency of the iron doping and a prospect how to improve spin polarization.

Towards Si-based spin transistor
K. Inomata
Spintronics devices have many potential applications, and have been commercialized in HDD and MRAM, which utilize the GMR and TMR effects. Spin transistors have been expected as future active devices, which use the heterostructures consisting of magnetic materials and semiconductors. The EFT type spin transistors studied up to now can be classified into two types, i.e., spin- FET proposed by Datta-Das and spin MOSFET. The former is well known, but scaling merits cannot be expected due to the long channel length required. In this seminar I will introduce a Si-based spin MOSFET and propose the two different types of the device structures.