Tweaking the spin-wave dispersion and suppressing the incommensurate phase in LiNiPO4 by iron substitution

Jiying Li, Thomas B S Jensen, Niels H. Andersen, Jerel L. Zarestky, R. William McCallum, Jaiho Chung, Jeffrey W. Lynn, David Vaknin

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

Elastic and inelastic neutron-scattering studies of Li (Ni1-x Fex) PO4 single crystals reveal anomalous spin-wave dispersions along the crystallographic direction parallel to the characteristic wave vector of the magnetic incommensurate phase. The anomalous spin-wave dispersion (magnetic soft mode) indicates the instability of the Ising-type ground state that eventually evolves into the incommensurate phase as the temperature is raised. The pure LiNiPO4 system (x=0) undergoes a first-order magnetic phase transition from a long-range incommensurate phase to an antiferromagnetic (AFM) ground state at TN =20.8 K. At 20% Fe concentrations, although the AFM ground state is to a large extent preserved as that of the pure system, the phase transition is second order, and the incommensurate phase is completely suppressed. Analysis of the dispersion curves using a Heisenberg spin Hamiltonian that includes interplane and in-plane nearest- and next-nearest-neighbor couplings reveals frustration due to strong competing interactions between nearest- and next-nearest-neighbor sites, consistent with the observed incommensurate structure. The Fe substitution only slightly lowers the extent of the frustration, sufficient to suppress the incommensurate phase. An energy gap in the dispersion curves gradually decreases with the increase in Fe content from ∼2 meV for the pure system (x=0) to ∼0.9 meV for x=0.2.

Original languageEnglish
Article number174435
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume79
Issue number17
DOIs
Publication statusPublished - 2009 May 1

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Spin waves
wave dispersion
Ground state
magnons
Substitution reactions
Iron
substitutes
frustration
iron
ground state
Phase transitions
Hamiltonians
Inelastic neutron scattering
curves
Dispersions
inelastic scattering
neutron scattering
Energy gap
Single crystals
single crystals

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Electronic, Optical and Magnetic Materials

Cite this

Tweaking the spin-wave dispersion and suppressing the incommensurate phase in LiNiPO4 by iron substitution. / Li, Jiying; Jensen, Thomas B S; Andersen, Niels H.; Zarestky, Jerel L.; McCallum, R. William; Chung, Jaiho; Lynn, Jeffrey W.; Vaknin, David.

In: Physical Review B - Condensed Matter and Materials Physics, Vol. 79, No. 17, 174435, 01.05.2009.

Research output: Contribution to journalArticle

Li, Jiying ; Jensen, Thomas B S ; Andersen, Niels H. ; Zarestky, Jerel L. ; McCallum, R. William ; Chung, Jaiho ; Lynn, Jeffrey W. ; Vaknin, David. / Tweaking the spin-wave dispersion and suppressing the incommensurate phase in LiNiPO4 by iron substitution. In: Physical Review B - Condensed Matter and Materials Physics. 2009 ; Vol. 79, No. 17.
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