Dipolar Spin Ice States with a Fast Monopole Hopping Rate in CdEr2X4 (X = Se, S)

Gao, ShangPaul Scherrer Institut, Switzerland; University of Geneva, Switzerland (author)

Foundation under Grants No. 20021-140862, No. 20020- 162626, and the SCOPES project No. IZ73Z0-152734/1.
Excitations in a spin ice behave as magnetic monopoles, and their population and mobility control the dynamics of a spin ice at low temperature. CdEr2Se4 is reported to have the Pauling entropy characteristic of a spin ice, but its dynamics are three orders of magnitude faster than the canonical spin ice Dy2Ti2O7. In this Letter we use diffuse neutron scattering to show that both CdEr2Se4 and CdEr2S4 support a dipolar spin ice state-the host phase for a Coulomb gas of emergent magnetic monopoles. These Coulomb gases have similar parameters to those in Dy2Ti2O7, i.e., dilute and uncorrelated, and so cannot provide three orders faster dynamics through a larger monopole population alone. We investigate the monopole dynamics using ac susceptometry and neutron spin echo spectroscopy, and verify the crystal electric field Hamiltonian of the Er3+ ions using inelastic neutron scattering. A quantitative calculation of the monopole hopping rate using our Coulomb gas and crystal electric field parameters shows that the fast dynamics in CdEr2X4 (X = Se, S) are primarily due to much faster monopole hopping. Our work suggests that CdEr2X4 offer the possibility to study alternative spin ice ground states and dynamics, with equilibration possible at much lower temperatures than the rare earth pyrochlore examples.

Zaharko, OksanaPaul Scherrer Institut, Switzerland (author)
Tsurkan, VladimirUniversity of Augsburg, Germany; Academy of Sciences of Moldova, Moldova (author)
Prodan, LilianAcademy of Sciences of Moldova, Moldova (author)
Riordan, EdvardCardiff University, UK (author)
Lago, JorgeUniversity of the Basque Country, Spain (author)
Fak, BjörnInstitut Laue-Langevin, France (author)
Wildes, Andrew R.Institut Laue-Langevin, France (author)
Koza, Marek M.Institut Laue-Langevin, France (author)
Ritter, ClemensInstitut Laue-Langevin, France (author)
Fouquet, PeterInstitut Laue-Langevin, France (author)
Keller, LukasPaul Scherrer Institut, Switzerland (author)
Canevet, EmmanuelPaul Scherrer Institut, Switzerland; DTU Technical University of Denmark, Denmark (author)
Medarde, MarisaPaul Scherrer Institut, Switzerland (author)
Blomgren, JakobRISE,Acreo(Swepub:ri)JakobBl@ri.se (author)
Johansson, ChristerRISE,Acreo(Swepub:ri)christer.johansson@ri.se (author)
Giblin, Sean R.Cardiff University, UK (author)
Vrtnik, StanislavJozef Stefan Institute, Slovenia (author)
Luzar, JoseJozef Stefan Institute, Slovenia (author)
Loidl, AloisUniversity of Augsburg, Germany (author)
Ruegg, ChristinaPaul Scherrer Institut, Switzerland; University of Geneva, Switzerland (author)
Fennell, TomPaul Scherrer Institut, Switzerland (author)
Paul Scherrer Institut, Switzerland; University of Geneva, SwitzerlandPaul Scherrer Institut, Switzerland (creator_code:org_t)

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