Magnetic behaviour of the quasi-doublet ground state of TmCuAl studied with the Tm169 Mössbauer pseudo-quadrupole shift

The hexagonal TmCuAl is studied with magnetic specific heat, resistivity and Tm169 Mössbauer spectroscopy measurements. TmCuAl orders antiferromagnetically at TN=1.9  K. The distance between the two levels of the quasi-doublet ground state of TmCuAl, determined with the Tm169 Mössbauer pseudo-quadrupole shift, amounts to 2.8(3) K. Based on the temperature dependence of the Tm169 quadrupole splitting a provisional calculation has been made for the crystal field diagram with a coupling constant α, which is non zero.