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MA: Magnetismus

MA 5: Spinstrukturen und magnetische Phasenüberg
änge

MA 5.11: Vortrag

Freitag, 4. März 2005, 13:00–13:15, TU EMH225

Neutron Crystal Field Spectroscopy on the Antiferroquadrupolar system TmGa₃ — •Michael Banks¹, Reinhard K Kremer¹, Danny Mannix², and Amir Murani³ — ¹MPI-FKF, 70569 Stuttgart — ²ESRF Grenoble, CEDEX 9 — ³ILL Grenoble, CEDEX 9

At room temperature TmGa₃ crystallizes with the cubic Cu₃Au structure type. At low temperature it undergoes two first order phase transitions, ascribed to a antiferroquadrupole (AFQ) ordering at 4.29K and an antiferromagnetic (AFM) transition at 4.26K. The Crystal Electric Field (CEF) ground state of the trivalent Tm³⁺ (4f¹², J = 6) in the cubic crystal field environment given by an earlier study [1] to ascertain the CEF parameters (in the Lea-Leask-Wolf scheme [2]) arrived at values of x=0.32, W=1.03K with a Γ₅⁽¹⁾ ground state separated by the first excited state Γ₃ at 2.5meV. To investigate possible quadrupolar splittings of the CEF levels we performed inelastic neutron scattering. Surprisingly, our level scheme suggests a Γ₂ singlet CEF ground state with the first excited state being a Γ₁ singlet and Γ₅⁽²⁾ triplet at ∼0.5 meV, which are almost degenerate, adverse to previous findings [1].

[1] P. Morin et al., J. Mag. Mag. Mat., 66, 345 (1987)

[2] K.R. Lea et al., J. Phys. Chem. Solids, 23, 1381 (1962)