Interlayer coupling in NiFe/Mo multilayers and effect of Fe underlayer

We report our studies of exchange coupling in NiFe/Mo multilayers with and without Fe underlayer. The interlayer coupling of NiFe layers across the Mo spacer as well as the magnetic exchange coupling between Fe underlayer and the NiFe/Mo multilayers were observed: The interlayer coupling in NiFe/Mo multilayers exhibits the typical oscillations as a function of the Mo spacer with a period of about 11 Angstrom, and the magnetic exchange coupling between Fe underlayer and the NiFe/Mo multilayers is strongly dependent on the thickness of the Mo spacer t(Mo) and the bilayer number N of NiFe/Mo multilayers. For the [NiFe(20 Angstrom)/Mo(t(Mo))](30) samples with a 100 Angstrom Fe underlayer, the hysteresis loops with thinner Mo spacer (t(Mo) < 4 Angstrom) are single loops indicating that the Fe underlayer is strongly magnetic exchange coupled with the NiFe/Mo multilayers; whereas hysteresis loops with thicker Mo spacer (t(Mo) greater than or equal to 5 Angstrom) show a two-magnetic-phase feature. For the [NiFe(20 Angstrom)/Mo(10 Angstrom)](30) Sample with 100 Angstrom Fe underlayer, the hysteresis loops are single loops for bilayer number N < 15, while hysteresis loops show the two-phase feature for N greater than or equal to 15. (C) 1997 American Institute of Physics.