AVS 53rd International Symposium
    Magnetic Interfaces and Nanostructures Wednesday Sessions
       Session MI-WeA

Paper MI-WeA4
A Novel Scheme for Pinning Magnetic Layers in Current Perpendicular to the Plane Spin Valve Devices

Wednesday, November 15, 2006, 3:00 pm, Room 2006

Session: Exchange Bias & TMR
Presenter: C. Papusoi, University of Alabama
Authors: C. Papusoi, University of Alabama
Z. Tadisina, University of Alabama
S. Gupta, University of Alabama
H. Fujiwara, University of Alabama
G.J. Mankey, University of Alabama
P. LeClair, University of Alabama
Correspondent: Click to Email
When an antiferromagnetic (AF) film is used to create anisotropy in a ferromagnetic (F) layer, the thickness of the AF is usually chosen to be greater than 5 nm to produce large loop shift of the pinned F layer. In current perpendicular to the plane (CPP) spin valves it is desirable for ancillary layers such as the AF to have a small electrical resistance. This creates a problem, since a fundamental property of antiferromagnets is an intrinsic high resistivity. A possible solution to this problem is to fabricate a device with a thinner AF layer (~2-4 nm) such that the coercivity of the F layer is enhanced while the loop shift is not fully developed. In this regime, the relaxation time of the AF grains is short enough to allow the AF surface moments to follow the F moments in an irreversible manner, due to the AF anisotropy, resulting in a supplementary loss mechanism and a substantial increase in the coercivity of the F layer. If the F layer is then replaced by a synthetic antiferromagnet (SAF), the applied field range where the SAF moments are antiparallel is enhanced with a concurrent increase in the giant magnetoresistance ratio (GMR). The thermal stability of spin valve stacks with the structure Ta(4)/Cu(10)/IrMn(x)/CoFe(3)/Ru(0.8)/CoFe(3)/Cu(2.5)/CoFe(1)/NiFe(3)/Ta(5) with x < 5 nm, is found to increase with increasing x. Magnetization and GMR measurements are compared to Stoner-Wohlfarth simulations which nicely show the applied field dependence of the relative orientations of the F layer magnetizations in the spin valve stack. These results will be compared to those obtained for similar spin valve stacks with thicker AF layers and stacks employing hard F layers to increase the pinned layer anisotropy.