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New Materials for High Moment Poles and Shields

Final Report Summary - NU-MATHIMO (New Materials for High Moment Poles and Shields)

The ever-expanding demand of the world market leads to magnetic recording data storage devices advancing toward much smaller dimensions and higher storage capacities. In order to achieve capacities beyond TB/in2, next generation magnetic recording head transducers will require improved high moment magnetic material together with novel write pole and shield structures to preserve the necessary magnetic flux on reduced device dimensions. The implementation of novel high moment magnetic materials and design in manufactured products requires the attainment of new knowledge by the magnetics industry along with the response of the academic industry to the new performance challenges.

To achieve these goals, a strong collaborative programme between industry and academia was required. The aim of NU-MATHIMO, a Marie Curie Industry-Academia Partnership Pathways (IAPP) Project funded by the FP7 People Program, was to study the properties of magnetic materials to enable higher moment than the presently attainable limits. The knowledge was to be transferred through the cross-border secondment of staff and researchers between Seagate Technology Ireland (SEA), University of Duisburg-Essen (UDE) in Germany and Uppsala University (UPP) in Sweden, utilizing the complementary expertise of the three nodes regarding state-of-the-art experimental and computational techniques as well as device fabrication.

Nineteen Marie Curie Early Stage and Experienced Researchers worked on the NU-MATHIMO project. Three researchers were recruited explicitly for the project and the others undertook inter-sectoral secondments of varying lengths. All NU-MATHIMO researchers received training in essential modern disciplines to help enhance their future career prospects in their chosen sector. The newly recruited researchers have brought new knowledge to the separate sectors and helped to drive the system level component of the research programme. The seconded UDE and UPP researchers, which included both theoreticians and experimentalists, have learned about several aspects of the magnetics industry through the training programmes at SEA. It is a particular success of this project that three of the NU-MATHIMO researchers were subsequently hired by SEA.

The scientific achievements of the NU-MATHIMO project include

• The development of Kinetic Monte Carlo code by UPP which is capable of taking input from ab-initio calculations to calculate atomic diffusion across different interfaces of heterostructures comprised of rare earth and transition metal layers.

• The experimental validation of new high moment materials identified as theoretically predicted by UPP. By a combination of first-principles density functional theory and experimental studies, UDE determined the structural, electronic and magnetic properties of Fe/X/Gd heterostructures with X being 3d transition metal as the spacer between Fe and Gd. This systematic study of the magnetic coupling between high critical temperature and high spin magnetic moment ferromagnets may open the route for the realization of a device based on transition metals and rare earth superlattices.

• A simulated comparison of the magnetic switching behaviour of write poles with a high moment-high anisotropy magnetic multilayer (such as Gd/Cr/CoFe) to a write pole without the multilayer structure was carried out at SEA. The switching behaviour of the multilayer write pole is acceptably close to the non-multilayer pole behaviour. This indicates that if these multilayer structures can be engineered to yield at sufficiently high reliability for high volume manufacturing of recording heads then their integration into the recording head structure will not present a huge challenge.

• Designs for recording heads which can incorporate rare-earth materials and industrial demonstration by SEA that addition of rare-earth materials can be reliable in an operating recording head.

As a result of the secondments between the industrial and academic partners and the collaborative research carried out during the NU-MATHIMO project, a major transfer of inter-sectoral knowledge and expertise in nano-magnetics, advanced materials, modelling and hard drive development has been achieved. Fourteen researchers (both early stage and experienced) were seconded from UDE and UPP to SEA. The academic researchers transferred expertise and knowledge on advanced magnetic materials development to SEA whilst receiving training in system design and modelling and gaining exposure to the work environment at SEA. SEA also seconded an Early Stage Researcher to UDE bringing practical industrial experience into the academic research group by informing the academic researchers on the approach and methods of work in the industrial sector whilst receiving training in element specific investigations utilizing Mössbauer spectroscopy at UDE and X-ray magnetic circular dichroism at the synchrotron radiation facility BESSY II.

To encourage and strengthen the transfer of knowledge, two events were organised by the NU-MATHIMO project. In 2015 UPP hosted a Summer School and Workshop where several prominent scientists from Europe and USA presented state-of-the-art topics in magnetism. In 2017 SEA hosted an International Conference / Autumn School focussed on the identification of new functional magnetic materials. Experts from fundamental research and applied technology gathered to present a broad overview of this field. Both events were well attended by external participants as well as the NU-MATHIMO researchers.

The NU-MATHIMO project has contributed to the training of several early stage researchers at UDE and UPP who have disseminated their results through presentations at conferences, publications in Scientific Reports and J. Phys. Condens. Mat. and reports both within SEA, UDE and UPP as well as to the wider hard disk drive and epitaxial thin film and multilayer communities. The dissemination of the results has helped to create a distinct profile for UDE and UPP in this scientific area.

The work carried out as part of NU-MATHIMO has delivered new insights into the understanding and exploitation of new materials featuring high moment pole and shield characteristics. These insights will be used in the future to help improve hard drive areal densities with these materials.

An important outcome of NU-MATHIMO has been to establish the basis for long-term collaboration between the academic and industrial partners. The partners have agreed a plan for future cooperation across several research areas, including alternative data storage, photonic materials and magnetic measurements, and are currently exploring mechanisms to fund this future research. As SEA have recruited two of the UDE NU-MATHIMO researchers, this will also lead to stronger links between UDE and SEA.

For more information about the project and how to contact us, please visit the website at www.nu-mathimo.eu.