Interactions in Nanoscale Arrays of Soft Magnetic Bi-Layers
Magnetic bi-layers are becoming increasingly popular as a medium for perpendicular patterned media. In order to understand the net interactions between the layers and between adjacent magnetic elements in an array, we use a coupled Preisach model to model the hysteresis loops we measured for a sample consisting two magnetically soft layers of FeCoTaZr, separated by an 0.8-nm Ru spacer layer. The model reproduces the major hysteresis loop to decent agreement. The model was then decoupled to reveal the reversal behavior of the individual layers. This paper demonstrates that coupled Preisach modeling of the hysteresis loop is an effective tool to analyze such interacting material systems.
Temperature-dependent magnetization reversal in (Co/Pt)/Ru multilayers - eScholarship
Antiferromagnetically coupled (Co/Pt)/Ru multilayers with perpendicular anisotropy have been shown to exhibit both vertically and laterally correlated magnetization reversal modes. In this work, the magnetization reversal of a multilayer film whose layer thicknesses have been tuned to be at the phase boundary between the two reversal modes has been investigated as a function of temperature, using the first-order reversal curve (FORC) method. At high temperatures, reversal via vertically correlated stripe domains throughout the film thickness is observed, similar to that in Co/Pt films without the Ru spacers. At low temperatures, antiferromagnetic (AF) interlayer exchange coupling dominates, and laterally correlated reversal is observed with an AF coupled remanent state. Under magnetic field cycling, dipolar fields can transform the sample back into a vertically correlated domain state, thus leading to an exotic behavior with FORC's existing outside the major hysteresis loop. Calculations show that the laterally correlated reversal mode is indeed slightly more stable, and the crossover to vertically correlated reversal can be induced by temperature as well as magnetic field.
Composite perpendicular magnetic recording media using [Co∕PdSi]n as a hard layer and FeSiO as a soft layer
We fabricated the composite perpendicular magnetic recording (PMR) media successfully for the first time by combining a nanogranular FeSiO soft layer and a [Co∕PdSi]n hard layer. PdSi spacing layer (0–4nm) was used to study the exchange coupling effects between the FeSiO(5nm) and the [Co(0.26nm)∕Pd(1nm)]14 layers in the composite films. Proper coupling occurs when PdSi interlayer is ∼0.5nm. Significant lowering of the coercivity is observed for the composite PMR medium while still maintaining good thermal stability. The results prove the possibility to fabricate a writable PMR medium having an ultrahigh magnetic anisotropy constant Ku value.