Development of magnetically switchable high permittivity microwave dielectrics using La(Al1-xFex)O3

Justin Gonzales, Siddhesh Gajare, Nathan Newman

Research output: Contribution to journalArticlepeer-review


The introduction of transition metal doping, particularly Fe3+, into high-performance microwave dielectrics can make “smart” materials that switch between a high-Q, low loss state and a low-Q, high loss state using a small external magnetic field. In this study, the dielectric and magnetic properties of the high permittivity host material LaAlO3r = 22.5), when doped with Fe3+, are reported. Spin losses dominate the loss tangent at cryogenic temperatures and survive up to room temperature. Peaks in the loss tangent versus temperature relation are observed near 40, 75, and 215 K. Additional measurements of samples exposed to annealing in varying environments, combined with Debye analysis and the results of native defect energy predictions from density functional calculations[Phys Rev B. 2009;80:104115], allows us to associate the 40, 75, and 215 K peaks to the following reactions, (Formula presented.), (Formula presented.), and (Formula presented.), respectively.

Original languageEnglish (US)
Pages (from-to)2669-2677
Number of pages9
JournalJournal of the American Ceramic Society
Issue number6
StatePublished - Jun 2021


  • dielectric materials/properties
  • electron paramagnetic resonance loss
  • polaron conduction
  • polaron loss
  • smart material
  • switchable device

ASJC Scopus subject areas

  • Ceramics and Composites
  • Materials Chemistry


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