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SUMMARY:Field-Induced Hidden Order in Magnetoelectric TbPO₄
DTSTART:20260112T133000Z
DTEND:20260112T143000Z
DTSTAMP:20260313T075700Z
UID:indico-event-610@indico.frm2.tum.de
CONTACT:Nicolas.Walte@frm2.tum.de\;d.saha@fz-juelich.de
DESCRIPTION:Speakers: Rasmus Toft-Petersen (European Spallation Source)\n\
 nIn magnetic f-electron systems\, unquenched orbital angular momentum can 
 result in the ordering of multipolar moments\, often termed “hidden orde
 r” [1]. Although challenging to observe experimentally\, hidden order ca
 n give rise to novel phases\, such as octupole liquids [2]\, and may even 
 influence the emergence of superconductivity [3].\nFerroquadrupolar order 
 is well established in rare earth orthovanadates\, with TmVO₄ serving as
  a benchmark model system at ambient conditions. This study centers on the
  more intricate compound TbPO₄\, notable for its exceptionally strong ma
 gnetoelectric coupling [4\,5]. TbPO₄’s complex low-energy crystal fiel
 d level scheme and pronounced magnetostriction lead to a rich phase diagra
 m\, and near-degeneracy of the magneto-elastic ground state is hypothesize
 d to be the underlying cause of the soft mode behavior leading to the stro
 ng magnetoelectric effect.\nOur recent investigations reveal a striking fi
 eld-induced ferroquadrupolar phase\, stemming from magnetoelastic interact
 ions. Using synchrotron X-ray and neutron diffraction\, heat capacity meas
 urements\, and mean-field modeling\, we demonstrate that above a critical 
 magnetic field\, ferroquadrupolar order becomes the dominant order paramet
 er\, competing with field-induced magnetic polarization. This is evidenced
  by significant lattice distortion and suppression of dipolar antiferromag
 netic order. Additionally\, magnetoelastic hybrid modes\, explored with th
 e CAMEA spectrometer\, show a multifaceted character and highlight the nec
 essity of studying magnetic dynamics across different phases to fully unde
 rstand such complex materials. I will be discussing our recent diffraction
  results and the magnetoelastic phase diagram\, as well as the status of 
 our ongoing efforts to understand the magnetoelastic dynamics.   \n[1] P
 . Santini et al.\, Rev. Mod. Phys. 81\, 807 (2009).[2] R. Sibille et al.\,
  Nat. Phys. 16\, 546 (2020).[3] C. Pfleiderer\, Rev. Mod. Phys. 81\, 1551 
 (2009).[4] S. Bluck & H. G. Kahle\, J. Phys. 21\, 5193 (1988).[5] J. P. Ri
 vera\, Eur. Phys. J. B 71\, 299–313 (2009).\n\nhttps://indico.frm2.tum.d
 e/event/610/
LOCATION:PH HS 3 (Physics Department)
URL:https://indico.frm2.tum.de/event/610/
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