73rd Magnetic Materials Center Seminar
April 17, 2008, 9:00-
7th floor small seminar room, Sengen
CPP GMR spin valves using Co2Fe(1-x)Cr(x)Si Heuslar alloy.
H. S. Goripati
In tomorrow's talk I will discuss my recent attempts to make CPP GMR spin valves which include Atomic Force Microscopy (AFM) analysis of Cu spacer and its subseqent effect on CIP MR result in SiO2 and CPP measurement of spin valves deposited on MgO. The highest value obtained by CPP measurement is 0.87%. This gives a direction for my future work.

Halfmetallic anti ferromagnetic Heusler alloys.
A. Rajanikanth
Search for a Halfmetallic anti ferromagnets (HMAF) have recently gained much importace in spintronic materials research. In spintronics as the device size becomes smaller the stray fields deteriorate the properties of the device. For example the vortex formation or magetic domain formation reduces the flow of spin polarized current in the device. Hence in order to avoid such kind of problems half-metallic anti ferromagnets might be potential candidates. Though de Groot has predicted V7MnFe8Sb7In compound there were no experimental reports till date on this alloy. In this context Heusler alloys with Zt < 24 valance electrons might be suitable materials for investigation, since from Slater-Pauling, Mt = Zt-24 (Mt total magnetic moment, Zt total number of valance electrons) < 0. This kind of materials may be potential candidates for spin injection when compared to the Pure Fe. We measured a spin polarization of 55% for this alloy using point contact Andreev (PCAR) technique. Hence in this presentation I will discuss about the point contact spectroscopy of these alloys and the effect of disorder on the magnetization will also be discussed.

Co2FeAl0.5Si0.5 (CFAS) layers annealing temperature dependence of TMR properties for full-epitaxial CFAS/MgO/CFAS MTJs
W. H. Wang
In this presentation, I will show the CFAS layers annealing temperature dependence of TMR properties for the sputter-deposited full-epitaxial CFAS/MgO/CFAS MTJs. We found that the MTJ with L21-ordered CFAS electrodes shows the largest TMR ratio of 150% at RT and 320% at 7 K. However, these values are much lower than expected from the half-metallicity of CFAS. To solve this problem, we further performed in-situ reflective high-energy electron diffraction (RHEED) and cross-section transmission electron microscopy (TEM) observations to investigate the growth process and microstructure of CFAS/MgO/CFAS MTJs. The results indicate that the low TMR ratio may be due to the poor interface/surface of sputtered MgO barrier