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

Abstract

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 Å, and the magnetic exchange coupling between Fe underlayer and the NiFe/Mo multilayers is strongly dependent on the thickness of the Mo spacer tMo and the bilayer number N of NiFe/Mo multilayers. For the [NiFe(20 Å)/Mo(tMo)]30 samples with a 100 Å Fe underlayer, the hysteresis loops with thinner Mo spacer (tMo<4 Å) 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 (tMo⩾5 Å) show a two-magnetic-phase feature. For the [NiFe(20 Å)/Mo(10 Å)]30 sample with 100 Å Fe underlayer, the hysteresis loops are single loops for bilayer number N<15, while hysteresis loops show the two-phase feature for N⩾15.