Magnetic Characterization of Perpendicular Recording Media

Developing a nanostructured material to fit the design criteria for perpendicular magnetic recording (PMR) media requires a multiple approach, which involves the investigation of structural, microstructural and magnetic properties, analytical and numerical simulations as well as recording tests to evaluate the material's read/write performance. Studying the magnetic properties represents a challenging task as the magnetic behavior of materials for PMR media is governed by a complex interplay among intrinsic material properties, magnetic interactions and various sources of microscopic inhomogeneity, the overall properties being further complicated by thermal effects that lead to time-dependent magnetic phenomena. Moreover, the magnetic behavior of systems with perpendicular anisotropy is significantly affected by the presence of strong demagnetizing fields that, in principle, should be corrected in all magnetic measurements for a proper investigation. This chapter will provide an overview of both basic and advanced magnetic characterization methods, mainly based on magnetometry techniques, commonly used to investigate the magnetic behaviour of materials for PMR media in relation to the requirements for high-density recording. Section I will provide a selection of methodologies for the investigation of granular thin films with perpendicular anisotropy, which are used in currently available PMR media being also at the basis of future recording systems. All the methods discussed in this section are also suitable for the characterization of exchange coupled composite systems and next generation bit patterned magnetic recording media, the analysis of their most relevant magnetic properties being discussed in sections II and III, respectively. Section IV will focus on the energy assisted magnetic recording (EAMR) technology by reporting on some specific measurements needed to verify if a material is able to match the peculiar requirements for the application.