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 Ang strom/CrMnPt D Angstrom/Ta 30 Angstrom were made with various CrMnPt t hicknesses indicated D. Shift fields of the hysteresis loop indicated H-p and coercivities indicated H-c were evaluated. With the increase o f 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 decreas es. 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 u sing the grain size distribution. Quantitatively, the calculated resul ts agree with the experimental results. The change of temperature depe ndence 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 t emperature becomes higher and the local blocking temperature shows nar rower 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 Physi cs.