Thickness effect on ferro/antiferromagnetic coupling of Co/CrMnPt systems

To investigate ferro/antiferromagnetic coupling in Co/CrMnPt layers of spin valve films, spin valve films of glass/Ta/NiFe/CoFe/Cu/Co 30 Angstrom/CrMnPt D Angstrom/Ta 30 Angstrom were made with various CrMnPt thicknesses indicated D. Shift fields of the hysteresis loop indicated H-p and coercivities indicated H-c were evaluated. With the increase of D from 150 to 1000 Angstrom, the blocking temperature increases from RT to 340 degrees C. By increasing the temperature, the coercivity H-c increases, peaks at around the blocking temperature and then decreases. The temperature at which H-c peaks increases with an increase of D. The maximum value of H-c decreases with the increase of D. The grain size distribution of CrMnPt was measured and temperature dependencies of H-p and H-c were calculated based on a thermal fluctuation model using the grain size distribution. Quantitatively, the calculated results agree with the experimental results. The change of temperature dependence of H-p and H-c an explained by the change of the local blocking temperature distribution. With the increase of D, the mean blocking temperature becomes higher and the local blocking temperature shows narrower distributions. The anisotropy constant of the antiferromagnet K-a0, which is a fitting parameter, increases with the increase of D and saturates at above 400 Angstrom. (C) 1998 American Institute of Physics.