Eu2CuO4: An anisotropic Van Vleck paramagnet

Abstract

Magnetic susceptibility measurements have shown anisotropic Van Vleck paramagnetism in ${\mathrm{Eu}}_2$ ${\mathrm{CuO}}_4$ single crystals. This behavior is associated with the singlet ground state ${(}^7$ ${\mathrm{F}}_0$) of ${\mathrm{Eu}}^{3+}$ ions, and the measured anisotropy is related to a crystal-field splitting of the excited multiplets ${(}^7$ ${\mathrm{F}}_{\mathrm{J}}$). From the experimental data at low temperatures (T≲50 K) a crystal-field parameter $A_2^0$〈$r^2$〉=-93(5) ${\mathrm{cm}}^{\mathrm{-}1}$ and a spin-orbit coupling constant ζ=303(15) ${\mathrm{cm}}^{\mathrm{-}1}$ 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.