First-order transition in the itinerant ferromagnet CoS 1.9Se0.1

Taku J Sato, J. W. Lynn, Y. S. Hor, S. W. Cheong

Research output: Contribution to journalArticlepeer-review

Abstract

Undoped CoS2 is an isotropic itinerant ferromagnet with a continuous or nearly continuous phase transition at TC = 122 K. In the doped CoS1.9Se0.1 system, the Curie temperature is lowered to TC = 90 K, and the transition becomes clearly first order in nature. In particular we find a discontinuous evolution of the spin dynamics as well as strong time relaxation in the ferromagnetic Bragg intensity and small-angle neutron scattering in the vicinity of the ferromagnetic transition. In the ordered state the long-wavelength spin excitations were found to be conventional ferromagnetic spin waves with negligible spin-wave gap (<0.04 meV), indicating that this system is also an excellent isotropic (soft) ferromagnet. In a wide temperature range up to 0.9TC, the spin-wave stiffness D(T) follows the prediction of the two-magnon interaction theory, D(T) = D(0)(1 - AT5/2), with D(0) = 131.7 ± 2.8 meV Å 2. The stiffness, however, does not collapse as T → T C from below. Instead a quasielastic central peak abruptly develops in the excitation spectrum, quite similar to results found in the colossal magnetoresistance oxides such as (La-Ca)MnO3.

Original languageEnglish
Article number214411
Pages (from-to)2144111-2144118
Number of pages8
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume68
Issue number21
Publication statusPublished - 2003 Dec 1
Externally publishedYes

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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