Origin of the non-magnetic phase transition in PrTi2Al20, reported earlier in the macroscopic study, has been asserted microscopically using elastic and inelastic neutron scattering techniques. It has been shown spectroscopically that the crystalline-electric-field ground state is a non-magnetic Γ3 doublet, whereas the excited states are two triplets (Γ4 and Γ5) and a singlet (Γ1). The diffraction experiment under external magnetic field shows that the non-magnetic transition is indeed ferro-quadrupolar ordering, which takes place as a consequence of cooperative removal of the ground-state-doublet degeneracy. It is therefore concluded that PrTi2Al20 is another rare example of Pr compounds exhibiting non-magnetic quadrupolar order.
@article{arxiv.1108.3705,
title = {Ferro-quadrupolar ordering in PrTi$_2$Al$_{20}$},
author = {Taku J Sato and Soshi Ibuka and Yusuke Nambu and Teruo Yamazaki and Akito Sakai and Satoru Nakatsuji},
journal= {arXiv preprint arXiv:1108.3705},
year = {2013}
}