Eu2CuO4: An anisotropic Van Vleck paramagnet

Abstract

Magnetic susceptibility measurements have shown anisotropic Van Vleck paramagnetism in Eu~Cu04 single crystals. This behavior is associated with the singlet ground state (Fo) of Eu'+ ions, and the measured anisotropy is related to a crystal-field splitting of the excited multiplets (F&). From the experimental data at low temperatures (T~50 K) a crystal-field parameter A2(r) =-93(5) cm ' and a spin-orbit coupling constant /=303(15) cm ' have been estimated. The temperature dependence of the magnetic susceptibility is predicted in terms of the Boltzmann population of the excited multiplets, and a comparison with experimental data up to 350 K is made. The possibility of a magnetic contribution arising from the Cu ions is discussed in connection with some discrepancies observed between the experimental and calculated magnetic susceptibilities.

Spin-order-dependent Raman scattering inRuSr2GdCu2O8<

“…We have also discarded alternative explanations to this peak which involved: ͑i͒ a structural phase transition associated with T C that could explain the apperance of a ''soft''-phonon mode, simply because this seems unlikely according to x-ray and neutron-scattering data, 30,31 and ͑ii͒ a more complex magnetic structure, as, e.g., a ferrimagnetic phase or a canted antiferromagnetic lattice which could more naturally explain the observation of two magnon scattering, 12 because this is incompatible with the published magnetic data. 3,4 Measurements in a sample where Gd is replaced by Eu 3 ͑which is a van-Vleck paramagnet with temperature independent magnetic susceptibility of the order of 1/20 that of Gd 3 at 40 K͒, 36 where the Ru-rare-earth coupling should be strongly reduced, show a smaller ''magnon'' peak, as seen in the inset of Fig. 2.…”

Ferromagnetic correlations and mixed Ru valence in the magnetic superconductorRuSr2(Eu,Gd)Cu

“…Because of the proximity of excited J multiplets to the Jϭ0 ground state the susceptibility is usually described using the Van Vleck formula. 7 At low temperatures the Van Vleck susceptibility is temperature independent and M vs H curves remain linear at 5 K with fields of 50 kOe. ͑ii͒ Core diamagnetism: This correction is specially important at high temperatures.…”

“…The only free parameter in the calculation of the Van Vleck susceptibility ͓(T ϭ0 K)ϳ7.1ϫ10 Ϫ3 emu/mol Eu 3ϩ ͔ was taken from the measurements in Eu 2 CuO 4 . 7 The susceptibility of Eu123 ( Eu123 ) can be very well described as Eu123 ϭ Eu 3ϩϩ 0 with 0 ϭ8.7ϫ10 Ϫ4 emu/mol. Below 250 K this correction was used instead of performing the direct subtraction of Eu123 .…”

Dzyaloshinsky-Moriya spin canting in the low-temperature tetragonal phase ofLa2−x−yEuySrxHücker1, Kataev2, Pommer3 et al. 2004Phys. Rev. B

“…The Van Vleck magnetism (solid lines) was calculated using a similar approach as in Ref. 52, which we have improved so that χ V V (Eu) is correctly described at higher temperatures which was a major problem in Ref. 52 and 53.…”