Direct observation of the ground state of a 1/3 quantum magnetization   plateau in SrMn$_3$P$_4$O$_{14}$ using neutron diffraction measurements
  We can directly investigate the ground state in magnetization-plateau fields (plateau ground state) using neutron diffraction measurements. We performed neutron diffraction measurements on the spin-5/2 trimer substance SrMn$_3$P$_4$O$_{14}$ in magnetization-plateau fields. The integrated intensities of magnetic reflections calculated using an expectation value of each spin in a plateau ground state of an isolated-trimer model agree well with those obtained experimentally in the magnetization-plateau fields. We succeeded in direct observation of a plateau ground state in SrMn$_3$P$_4$O$_{14}$. 
Masashi Hase, Vladimir Yu. Pomjakushin, Andreas Doenni, Tao Yang,   Rihong Cong, and Jianhua Lin
cond-mat.str-el