Reversible disorder in a room temperature ferromagnet

Spencer L. Tomarken, Daniel M. Silevitch, Gabriel Aeppli, Braden A.W. Brinkman, Jian Xu, Karin A. Dahmen, Thomas F. Rosenbaum

Research output: Contribution to journalArticlepeer-review


Random magnetic fields, varying from site to site in a magnetic material, are a form of disorder that can determine the local architecture and stability of the magnetic state. In a ferromagnet, the application of an external magnetic field can amplify the effects of the internal random fields and, in principle, harden a magnetic domain, without changing temperature and only for as long as the external field is present. Here, the rare-earth compound Nd 2Fe14B, formed with a granular morphology of random-packed, elongated grains, is an experimental realization of the Random Field Ising Model in a room temperature ferromagnet. The application of magnetic fields transverse to the easy axis tunes the coupling between the structural disorder and the magnetic pinning properties. This material both illuminates the intricacies of tunable disorder and serves as a guidepost along the way to developing increased-density magnetic storage media. Application of a transverse magnetic field can reversibly tune the magnetic hardness of a disordered uniaxial, high anisotropy rare earth magnet at room temperature. Random field effects control the effective strength of the material's intrinsic disorder, providing a convenient control knob for rapidly and isothermally switching between different computationally relevant magnetic characteristics.

Original languageEnglish (US)
Pages (from-to)2986-2992
Number of pages7
JournalAdvanced Functional Materials
Issue number20
StatePublished - May 28 2014


  • disorder
  • ferromagnetism
  • ferromagnets
  • Ising model
  • random fields
  • rare earths

ASJC Scopus subject areas

  • Biomaterials
  • Electrochemistry
  • Condensed Matter Physics
  • Electronic, Optical and Magnetic Materials

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