Under zero magnetic field, a quadrupolar order parameter at q_Q=(1/2,1/2,1/2) in a typical antiferro-quadrupole (AFQ) ordering compound CeB6 has been observed for the first time by means of a resonant X-ray scattering (RXS) te\ chnique. The RXS is observed at the 2p->5d dipole transition energy of the Ce L3-edge. Using this RXS technique to observe the pure order parameter of the AFQ state, the magnetic phase diagram of Phase II is first determined.
@article{arxiv.cond-mat/0106183,
title = {Antiferro-quadrupole Ordering of CeB$_6$ Studied by Resonant X-ray Scattering},
author = {Hironori Nakao and Ko-ichi Magishi and Yusuke Wakabayashi and Youichi Murakami and Kuniyuki Koyama and Kazuma Hirota and Yasuo Endoh and Satoru Kunii},
journal= {arXiv preprint arXiv:cond-mat/0106183},
year = {2009}
}