The planar triangular S = 3/2 magnet AgCrSe2 : magnetic frustration, short range correlations, and field tuned anisotropic cycloidal magnetic order
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Our studies evidence an anisotropic magnetic order below TN = 32~K. Susceptibility data in small fields of about 1~T reveal an antiferromagnetic (AFM) order for H ⊥ c, whereas for H || c the data are reminiscent of a field-induced ferromagnetic (FM) structure. At low temperatures and for H ⊥ c, the field-dependent magnetization and AC susceptibility data evidence a metamagnetic transition at H+ = 5~T, which is absent for H || c. We assign this to a transition from a planar cycloidal spin structure at low fields to a planar fan-like arrangement above H+. A fully FM polarized state is obtained above the saturation field of H⊥S = 23.7~T at 2~K with a magnetization of Ms = 2.8~μB/Cr. For H || c, M(H) monotonously increases and saturates at the same Ms value at HIIS = 25.1~T at 4.2~K. Above TN, the magnetic susceptibility and specific heat indicate signatures of two dimensional (2D) frustration related to the presence of planar ferromagnetic and antiferromagnetic exchange interactions. We found a pronounced nearly isotropic maximum in both properties at about T* = 45~K, which is a clear fingerprint of short-range correlations and emergent spin fluctuations. Calculations based on a planar 2D Heisenberg model support our experimental findings and suggest a predominant FM exchange among nearest and AFM exchange among third-nearest neighbors. Only a minor contribution might be assigned to the antisymmetric Dzyaloshinskii-Moriya interaction possible related to the non-centrosymmetric polar space group R3m. Due to these competing interactions, the magnetism in AgCrSe2, in contrast to the oxygen based delafossites, can be tuned by relatively small, experimentally accessible, magnetic fields, allowing us to establish the complete anisotropic magnetic H-T phase diagram in detail.
Baenitz , M , Piva , M M , Luther , S , Sichelschmidt , J , Ranjith , K M , Dawczak-Dȩbicki , H , Ajeesh , M O , Kim , S -J , Siemann , G , Bigi , C , Manuel , P , Khalyavin , D , Sokolov , D A , Mokhtari , P , Zhang , H , Yasuoka , H , King , P D C , Vinai , G , Polewczyk , V , Torelli , P , Wosnitza , J , Burkhardt , U , Schmidt , B , Rosner , H , Wirth , S , Kühne , H , Nicklas , M & Schmidt , M 2021 , ' The planar triangular S = 3/2 magnet AgCrSe 2 : magnetic frustration, short range correlations, and field tuned anisotropic cycloidal magnetic order ' , Physical Review. B, Condensed matter and materials physics .
Physical Review. B, Condensed matter and materials physics
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DescriptionFunding: Deutsche Forschungsgemeinschaft (DFG) through the SFB 1143 and the Wurzburg-Dresden Cluster of Excellence on Complexity and Topology in Quantum Matter–ct.qmat (EXC 2147, Project No. 390858490), as well as the support of the HLD at HZDR, a member of the European Magnetic Field Laboratory (EMFL). We gratefully acknowledge support from the European Research Council (through the QUESTDO project, 714193), the Leverhulme Trust, and the Royal Society. We thank the Elettra synchrotron for access to the APE-HE beamline under proposal number 20195300. The research leading to this result has been supported by the project CALIPSOplus under Grant Agreement 730872 from the EU Framework Programme for Research and Innovation HORIZON 2020. Part of this work has been performed in the framework of the Nanoscience Foundry and Fine Analysis (NFFA-MUR Italy Progetti Internazionali) project (www.trieste.NFFA.eu).
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