Quadrupolar ordering and magnetic properties of tetragonal TmAu 2

摘要: Magnetic susceptibility, magnetization process, specific heat, ultrasonic velocity, and inelastic neutron scattering experiments were performed on powdered single-crystalline ${\mathrm{TmAu}}_{2}$ samples. with a simple body-centered tetragonal ${\mathrm{MoSi}}_{2}$-type structure undergoes transition to an antiferromagnetic state at ${T}_{N}$ of 3.2 K. An anomaly 7.0 K is observed in the temperature dependence heat magnetic susceptibility. A very large softening beyond 50% from 300 down also elastic constant ${C}_{11}\ensuremath{-}{C}_{12}$ mode. The results reveal clearly that ${(=T}_{Q})$ originates ferroquadrupolar ordering orthorhombic $\ensuremath{\gamma}$-symmetry-lowering Separation between ground first excited singlet states $4f$ levels so small quadrupolar ordered phase probability these extremely there occurs Van Vleck by exchange-induced moments arising states.