Magnetic vortex nucleation/annihilation in artificial-ferrimagnet microdisks

Pavel N. Lapa, Junjia Ding, Charudatta Phatak, John E. Pearson, J. S. Jiang, Axel Hoffmann, Valentine Novosad

Research output: Contribution to journalArticlepeer-review

Abstract

The topological nature of the magnetic-vortex state gives rise to peculiar magnetization reversal observed in magnetic microdisks. Interestingly, magnetostatic and exchange, energies which, drive this reversal can be effectively controlled in artificial ferrimagnet heterostructures composed of rare-earth and transition metals. [Py(t)/Gd(t)]25 (t = 1 or 2 nm) superlattices demonstrate a pronounced change of the magnetization and exchange stiffness in a 10-300 K temperature range as well as very small magnetic anisotropy. Due to these properties, the magnetization of cylindrical microdisks composed of these artificial ferrimagnets can be transformed from the vortex to uniformly magnetized states in a permanent magnetic field by changing the temperature. We explored the behavior of magnetization in 1.5-μm [Py(t)/Gd(t)]25 (t = 1 or 2 nm) disks at different temperatures and magnetic fields and observed that due to the energy barrier separating vortex and uniformly magnetized states, the vortex nucleation and annihilation occur at different temperatures. This causes the temperature dependences of the magnetization in these Py/Gd disks to demonstrate a unique hysteretic behavior in a narrow temperature range. It was discovered that for the [Py(2 nm)/Gd(2 nm)]25 microdisks, the vortex can be metastable within a certain temperature range.

Original languageEnglish (US)
Article number083903
JournalJournal of Applied Physics
Volume122
Issue number8
DOIs
StatePublished - Aug 28 2017
Externally publishedYes

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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