42nd Magnetic Materials Center Seminar
April 12, 2007, 9:00
7th floor seminar room, Sengen
Spin polarization results of CoTi1-XMnXSn
B. Varaprasad
Heusler alloys exhibit the possibility for enhanced current magnetoresistive devices. It is theoretically predicted 100% spin polarization is very interesting in terms of applications, but also from fundamental physical point of view. Ordering is one of the most important parameters in Heusler alloys to achieve high spin polarization. Co2TiSn is theoretically predicted to have high L21 ordering. Affect of Mn alloying and annealing on spin polarization is studied.

Comparison between Superconducting tunneling spectroscopy (STS) and point contact spectroscopy (PCAR)
A. Rajanikanth
The present research in spintronics is heading towards realizing 1000% tunneling magneto resistance (TMR) in magnetic tunneling junctions (MTJ) at room temperature (RT). For achieving high TMR, it is necessary to process the material such a way that it retains its intrinsic high spin polarization at RT. Heusler alloys are theoretically predicted to possess high spin polarization at RT. For measuring the spin polarization, point contact Andreev reflection (PCAR) is one of the most practical and easy methods. However, P values extracted from the Julliers formula for TMR and the PCAR method are in some cases not in good agreement with each other. Comparing the Spin polarization values measured by both PCAR and superconducting tunneling spectroscopy (STS) would reveal the intrinsic as well as the interfacial properties, which would provide useful information on the development of MTJs that exhibit very high TMR. I will discuss about my recent attempts on tunneling spectroscopy and some comparisons with the PCAR measurements.

CIPGMR of Co2FeAl0.5Si0.5/Cu/CoFe multi layered films
T. Furubayashi
Giant magnetoresistance (GMR) of three-layered thin films with the FM/NM/FM (FM: ferromagnetic metal, NM: non-magnetic metal) structure has been extensively investigated. It is highly pro misingfor obtaining high MR ratio to use a Heusler alloy Co2FeAl0.5Si0.5 (CFAS), which has the highest polarization ratio desuced from TMR among many kinds of heusler alloys. In this seminar, I describe the magnetic properties and the CIPGMR of multilayer ed films with the structure of CFAS/Cu/CoFe. Recently, a new ULVAC's sputtering machine was moved from Sendai and I started preparing films. I compare properties of the films prepared with the new machine with those prepared with the Eiko's machine in the room 444. Effects of sputtering conditions on the magnetic and MR properties are discussed.