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Using a combination of resonant soft x-ray scattering, magnetometry, x-ray reflectivity and microscopy techniques we have investigated the magnetic properties and microstructure of a series of perpendicular anisotropy Co/Pt multilayer films with respect to structural disorder tuned by varying the sputtering deposition pressure. The observed magnetic changes in domain size, shape and correlation length originate from structural and chemical variations in the samples, such as chemical segregation and grain formation as well as roughness at the surface and interfaces, which are all impacted by the deposition pressure. All samples exhibited short range "liquid-like" positional ordering over significant portions of their major hysteresis loops, while only the lowest disorder samples showed evidence of a random "gas-like" distribution of magnetic domains, present just after nucleation and as well as prior to saturation. The structural and chemical disorder induced by the higher deposition pressure first leads to an increase in the number of magnetic point defects that limit free domain wall propagation. Then, as the sputtering pressure is further increased, the domain wall energy density is lowered due to the formation of local regions with reduced magnetic moment, and finally magnetically void regions appear that confine the magnetic domains and clusters, similar to segregated granular magnetic recording media.

Articles you may be interested inStructure and magnetoresistance of current-perpendicular-to-plane pseudo spin valves using Co2Mn(Ga0.25Ge0.75) Heusler alloy

Magnetic and magnetotransport properties of current-perpendicular-to-the-plane (CPP) giant-magnetoresistance (GMR) spin-valve sensors containing the Heusler alloy Co2MnGe are presented. The geometrical and head integration constraints which exist for recording head applications are discussed and dictate various design compromises which determine the final device properties. Here we show that even for small total sensor thicknesses 400 Å and anneal temperatures < 250 °C we can obtain CPP-GMR signal levels up to ΔRA = 4 mΩ-μm2 at room temperature when inserting Co2MnGe in both the free layer and reference layers of the spin valve. Output levels increase to 10 mΩ-μm2 when reducing the temperature below 100 K, demonstrating the strong temperature dependence of the spin-dependent scattering in the Co2MnGe-based magnetic layers.

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