Systematic control of stress-induced anisotropy in pseudomorphic iron garnet thin films

M. Kubota, K. Shibuya, Y. Tokunaga, F. Kagawa, A. Tsukazaki, Y. Tokura, M. Kawasaki

Research output: Contribution to journalArticlepeer-review

35 Citations (Scopus)

Abstract

Iron garnets are one of the most well-studied magnetic materials that enabled magnetic bubble memories and magneto-optical devices employing films with a perpendicular easy axis. However, most studies have been conducted on rather thick films (>1 μm), and it has not been elucidated whether it is possible to align the magnetic easy axis perpendicular to the film plane for much thinner (<100 nm) films by overcoming shape anisotropy. We studied the effects of epitaxial strain and film composition on the magnetic properties of 50-nm-thick garnet thin films grown by pulsed-laser deposition. Y 3Fe5O12 was selected as the most prototypical garnet and Sm3-xTmxFe5O12 (x=1, 2, 3) was selected in view of its negatively large magnetostriction constants. We employed (111) planes of single crystalline Gd3Ga5O 12 and (CaGd)3(MgGaZr)5O12 substrates to tune the epitaxial strain. Thin films with a pseudomorphic structure were fabricated with the in-plane strain (ε//) ranging from -1.5% to +0.5%, corresponding to the stress-induced anisotropy field (HA) ranging from -40 kOe to +25 kOe, respectively. The magnetization ratio of the out-of-plane to in-plane component (M/M //) systematically varied in accord with HA, yielding M/M// >1 for thin films with HA values larger than 20 kOe. Among the films grown, Tm3Fe5O 12 on Gd3Ga5O12 showed the largest ε// and HA values of +0.5% and +25 kOe, respectively, to realize an apparently perpendicular easy axis, confirmed by a large M /M// value of 7.8. Further, magnetic force microscope images showed a maze pattern typical of a perpendicularly magnetized film. These results reveal a method for tailoring the magnetic anisotropy of garnet ultrathin films by utilizing epitaxial strain. These thin films may be utilized to obtain nanoscale magnetic bubbles for use in novel devices.

Original languageEnglish
Pages (from-to)63-70
Number of pages8
JournalJournal of Magnetism and Magnetic Materials
Volume339
DOIs
Publication statusPublished - 2013 Aug

Keywords

  • Epitaxial strain
  • Iron garnet
  • Magnetic anisotropy
  • Pulsed-laser deposition (PLD)
  • Thin film

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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