Anisotropy Tuning in Co/Pd Multilayers: For Application in Exchange-Springs

UoM administered thesis: Phd

  • Authors:
  • Craig Barton

Abstract

Exchange-spring systems have been proposed as one method of addressing the media trilemma, where a balance must be maintained between thermal stability, writeability and signal to noise ratio. High anisotropy films coupled to low anisotropy films, in bit patterned media (BPM), via the exchange interaction allow the reversal mechanism to be tailored such that thermal stability is maintained whilst the switching field remains realisable in terms of available write elements. Understanding how the exchange interaction is mediated by through exchange break layers (EBL) is key in successfully creating an optimal exchange spring structure based on Co/Pd thin films for applications such as BPM.The work presented in this thesis shows that the perpendicular magnetic anisotropy (PMA) ofCo/Pd magnetic multilayers can be tuned by varying the Ar ion energy during deposition, usingremote plasma sputtering. This provides a novel method of tailoring the PMA without affecting the film composition and reduces the need for post fabrication processing. It is demonstrated that the reduction in PMA is due to chemical intermixing at the multilayer interface as the Ar ion energy is increased. This provides a method of creating two phase or graded exchange-spring materials for data storage or spin torque applications.In-situ anisotropy tuning was used to create hard and soft magnetic phases using Co/Pd multilayers to explore the effect of an exchange break layer (EBL) on exchange coupling. The relative coupling was investigated using Pd and Ta as the exchange break layer in two-phase anisotropy systems. The exchange-spring effect was found to extend 4 nm in the case of a Pd, whereas in the case of a Ta EBL only a 0.5 nm layer exhibited the same effect. These results highlight the importance of the choice of material for the EBL on the effective performance of the exchange-spring.

Details

Original languageEnglish
Awarding Institution
Supervisors/Advisors
    Award date31 Dec 2014