Ferromagnetic thin films with perpendicular magnetic anisotropy (PMA) provide an excellent support to develop media for high-density magnetic recording. To optimize the density of magnetic domains and control the magnetic response of the magnetic film to an applied magnetic field, further understanding of the domain pattern formation and evolution throughout the magnetization process is necessary. Here we study the in-situ morphology of magnetic domains in Co/PtN multilayered thin films with PMA via magnetic force microscopy (MFM). We found that the domain pattern evolves between three distinct topologies: bubble pattern, short stripe pattern, and maze pattern. Previous studies1-4 have demonstrated that the morphology of these patterns at remanence depends on the number of bilayer repeats, layer thickness, and maximum of the previously applied field. Here we extend the remanence study to explore the evolution of the domain patterns under in-situ magnetic field. Domain density and interdomain distance are key metrics for quantifying morphological changes in the domain patterns, as illustrated in Figure 1. Using MFM, we mapped the domain density and interdomain distance in response to the in-situ and maximum applied magnetic field up to 7.2 kOe. We completed these studies for layer repeats of N from 20 down to 10 and Co thicknesses from 30 Å down to 10 Å. We found three main types of in-situ phase transitions, which result in the previously observed remanent phase transitions Additionally, we found that the domain density is maximized with in-situ applied field when N = 20 with Co thicknesses of 30 Å.

References:

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2. K. Chesnel, A. S. Westover, C. Richards, B. Newbold, M. Healey, L. Hindman, B. Dodson, K. Cardon, D. Montealegre, J. Metzner, T. Schneider, B. Böhm, F. Samad, L. Fallarino and O. Hellwig, Physical Review B 98 (22), 224404 (2018).
   
3. Fallarino, A. Oelschlägel, J. A. Arregi, A. Bashkatov, F. Samad, B. Böhm, K. Chesnel and O. Hellwig, Physical Review B 99 (2), 024431 (2019).
   
4. A. Gentillon, C. Richards, L. A. Ortiz-Flores, J. Metzner, D. Montealegre, M. Healey, K. Cardon, A. Westover, O. Hellwig and K. Chesnel, AIP Advances 11 (1), 015339 (2021).