The layered perovskite cobaltite RBaCo2O5.5 (R: rare-earth elements or Yttrium) exhibits an abrupt temperature-induced metal−insulator transition (MIT) and has been attributed to spin-state ordering (SSO) of Co3+ ions. Here we investigated the hole doping member of PrBaCo2O5.5+x (0≤x≤0.24) with multiple techniques. The analysis on crystal and magnetic structures by electron and neutron diffraction confirm the SSO in the insulating phase of undoped PrBaCo2O5.5, which is melted by increasing the temperature across the MIT. In addition, we discovered that hole doping to PrBaCo2O5.5 also melts the SSO in conjunction with an insulator-metal transition. The experimental results from electron/neutron diffraction and soft x-ray absorption spectroscopy (XAS) all lead to the conclusion that hole-doping induced MIT occurs is in the same manner as the temperature-induced MIT. Therefore, we propose a unified mechanism that dominates the temperature- and hole-doping-induced MITs in the PrBaCo2O5.5+x system. Specifically, this mechanism involves symmetry breaking coupled with a SSO in the paramagnetic phase.
@article{arxiv.1602.05687,
title = {Hole-doping-induced melting of spin-state ordering in PrBaCo2O5.5+x},
author = {Ping Miao and Xiaohuan Lin and Sanghyun Lee and Yoshihisa Ishikawa and Shuki Torii and Masao Yonemura and Tetsuro Ueno and Nobuhito Inami and Kanta Ono and Yinxia Wang and Takashi Kamiyama},
journal= {arXiv preprint arXiv:1602.05687},
year = {2017}
}