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In this paper, an experimental investigation of current-induced noise in current perpendicular-to-plane spin-valve heads is reported. It is found that the sense current yields excitations of coherent spin waves as well as substantial 1/f-like noise when current exceeds a critical value. The noise is magnetic in nature. The criticality and current directional dependence of the noise excitation clearly show that the spin transfer is the cause. Index Terms--Current perpendicular-to-plane (CPP) spin-valve read heads, spin transfer, 1/f noise.

In this paper, we present a quantitative micromagnetic modeling analysis of head stability in in-stack biased current perpendicular to plane (CPP) spin valve (SV) heads at deep submicron track widths. It is found that sufficient pinning on the in-stack bias layer is the key for stability. The narrower track-width heads have better stability. For in-stack biased bottom SV heads, the conventional structure has serious stability problem due to weakened or reversed bias field at free layer track edge. Controlling CPP edge profile is crucial for stability. We also studied the effect of current field on head performance. Depending on the current direction, current field can either induce instability or assist head stability. Index Terms--CPP spin valve read heads, in-stack longitudinal bias, stability.

A study was conducted to analyze the influence of crystalline orientation and grain size on the switching behavior for patterned face-centered-cubic cobalt film elements. Micromagnetic modeling was utilized to carry out the analysis. Experimental results indicated that the switching field of the cobalt film element is significantly dependent on the crystalline orientation and grain size.

Spin valve memory element biased with a pair of antiparallel (AP) coupled ferromagnetic layer was analyzed and modeled via micromagnetic simulation. In an AP structure, an external field results in a torque, causing the antiparallel magnetization (AP) axis to rotate towards the direction orthogonal to the field. In addition, due to its strength difference between the two AP layers, the magnetostatic field from the free layer of the spin valve can lead to irreversible AP axis flipping. This irreversible flipping can be effectively prevented by applying an AF/F exchange pinning to one of the AP layers to overcome the differential field from the free layer. Index Terms - Spin valve MRAM, synthetic antiferromagnet

Micromagnetic modeling of submicron size pseudo spin valve memory elements is presented. The storage mechanism of the memory system is proposed. For this mechanism, the switching field of the hard layer and the back switching field of the soft layer need to be well separated to ensure the non-destructive read-out. As the size of the element is reduced, the back switching field of the soft layer greatly increases. It is found that this back switching field can be significantly reduced by introducing a transverse anisotropy field in the soft layer. It is also found that the existence of an antiparallel edge domain configuration in the memory element can significantly degrade the performance of the memory cell and cause instability.

This paper presents a systematic micromagnetic analysis on spin valve GMR memory elements. It is found that for submicron size spin valve elements, edge demagnetization field, arising from the pinned layer, results in significant magnetization curling at the end edges of the free layer. This edge demagnetization phenomenon yields significant degradation of device performance. It is proposed that by making the pinned film element slightly longer than the free layer so that the ends of the free and pinned layers are separated, the edge demagnetization in the free layer can be essentially eliminated.

In this paper, we present the vertical magnetoresistive random access memory (VMRAM) design based on micromagnetic simulation analysis. The design utilizes the vertical giant magnetoresistive effect of the magnetic multilayer. By making the memory element into a ring-shaped magnetic multilayer stack with orthogonal paired word lines, magnetic switching of the memory device becomes very robust. The design also adopts the readback scheme in pseudo spin valve MRAM so that only one transistor is needed for each bit line which can connect hundreds of memory elements, yielding a very high area density. It is estimated that the ultimate area density for the VMRAM is 400 Gbits/in.2. It is suggested that this memory design has the potential to not only replace the present semiconductor memory devices, such as FLASH, but also the potential to replace DRAM, SRAM, and even disk drives. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A micromagnetic study of synthetic antiferromagnet (SAF) biased spin valve heads with patterned exchange stabilization is presented. It is found that at deep sub-micron track widths, spin valve heads with the patterned exchange stabilization exhibit significantly higher read sensitivity than that stabilized with permanent magnet abutted junctions. It is also found that the canting of the exchange pinning field for the synthetic anti-ferromagnet layer off the vertical axis yields very different read sensitivity depending on the canting direction. Detailed analysis and explanation of the mechanism for the phenomenon are provided. It is concluded that the patterned exchange stabilization scheme can further extend the track density for the spin valve heads over the currently used stabilization scheme. Index Terms--Patterned exchange stabilization, spin valve heads.