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TT: Fachverband Tiefe Temperaturen
TT 65: Frustrated Magnets: General I
TT 65.6: Talk
Thursday, March 21, 2024, 10:45–11:00, H 2053
Anomalous critical exponents and other peculiarities of Li2CuO42 — •Stefan-Ludwig Drechsler1, Wolfram Lorenz1, Ulrich K. Rößler1, Roman Kuzian2, Waldemar Hergett3, and Rüdiger Klingeler3 — 1IFW-Dresden, Germany — 2Intern. Phys. Center, San Sebastian, Spain — 3Heidelberg University, Germany
We report anomalously small critical exponents for the sublattice magnetization of the critical exponent β for various single crystals of Li2CuO2 including recent data from the literature [1-3]. The obtained reduced values β < 0.37 as compared to the 3d-isotropic Heisenberg model are ascribed to a relevant magneto-elastic coupling especially along the c-axis and to the vicinity of a multicritical point to a non-collinear chiral phase resulting in the presence of Lifshits invariants (LI) in the free energy not yet considered so far for the highly symmetric lattice structure of Li2CuO2. The experimental Néel-temperature TN is analyzed in terms of frustrating interchain couplings derived from a spin-wave analysis of inelastic neutron scattering data [1] leading to a sizable lowering by about 30%. Slightly different values for the coupling constants as compared with [2] are interpreted in terms of a two-phased single crystal there leading to a sharp peak near 9.5 K and a broader shoulder near 9.1 K within a Fisher-plot for d (Tχ(T))/dT. Noteworthy is also a negative cusp near 2.5 K in the context of LI and weak ferromagnetism below 2.3 K.
[1] W.E.A. Lorenz et al., EPL 88 (2009) 37002
[2] E. Zoghlin et al., Phys. Rev. B 108 (2023) 064408
[3] E.M.L. Chung et al., Phys. Rev. B 68 (2003) 144410
Keywords: critical exponents; N\'{e}el-temperature; magneto-elastic coupling; frustration; multicritical point