Site Preferences and "Coloring Problem" in Cu-doped BiMn7O12 Quadruple Perovskite
Abstract
Lightly Cu-doped BiMn7O12 (x = 0.05, 0.10, and 0.15) was investigated using high-pressure synthesis, single-crystal X-ray diffraction, pair distribution function (PDF) analysis, STEM, magnetic measurements, and first-principles calculations. All compositions retain an average monoclinic I2/m structure, while Cu substitution progressively suppresses the monoclinic distortion and drives the lattice toward a pseudo-cubic metric symmetry. PDF analysis reveals increasing local structural disorder and reduced medium-range coherence with increasing Cu concentration, despite preservation of the overall quadruple-perovskite framework. Single-crystal refinements indicate enhanced electron density at the octahedral Mn B sites, suggesting preferential Cu occupation within the MnO6 network rather than the conventional square-planar sites expected for Cu2+. Magnetic measurements reveal two characteristic anomalies near T1 ~ 100-120 K and T2 ~ 50-60 K, together with pronounced magnetic irreversibility, field-dependent hysteresis, and unsaturated magnetization. Increasing Cu concentration progressively suppresses the low-temperature magnetic state and weakens the field-induced moment. First-principles calculations favor Cu occupation at the square-planar sites, contrasting with the experimental refinements and highlighting strong competitions among local bonding, short-range disorder, and metastability in this highly frustrated quadruple perovskite system.
Versions
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BibTeX
@misc{peng2026site,
title = {{Site Preferences and "Coloring Problem" in Cu-doped BiMn$_7$O$_12$ Quadruple Perovskite}},
author = {Cheng Peng and Mingyu Xu and Yang Zhang and Ismail El Baggari and Jie Li and Weiwei Xie},
howpublished = {arXiv},
year = {2026},
month = jun,
doi = {10.48550/arxiv.2606.12711},
eprint = {2606.12711},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.12711},
}
RIS
TY - UNPB
TI - Site Preferences and "Coloring Problem" in Cu-doped BiMn_7O_12 Quadruple Perovskite
AU - Cheng Peng
AU - Mingyu Xu
AU - Yang Zhang
AU - Ismail El Baggari
AU - Jie Li
AU - Weiwei Xie
PY - 2026
DA - 2026/06/10
PB - arXiv
DO - 10.48550/arxiv.2606.12711
UR - https://arxiv.org/abs/2606.12711
AB - Lightly Cu-doped BiMn_7O_12 (x = 0.05, 0.10, and 0.15) was investigated using high-pressure synthesis, single-crystal X-ray diffraction, pair distribution function (PDF) analysis, STEM, magnetic measurements, and first-principles calculations. All compositions retain an average monoclinic I2/m structure, while Cu substitution progressively suppresses the monoclinic distortion and drives the lattice toward a pseudo-cubic metric symmetry. PDF analysis reveals increasing local structural disorder and reduced medium-range coherence with increasing Cu concentration, despite preservation of the overall quadruple-perovskite framework. Single-crystal refinements indicate enhanced electron density at the octahedral Mn B sites, suggesting preferential Cu occupation within the MnO_6 network rather than the conventional square-planar sites expected for Cu^2+. Magnetic measurements reveal two characteristic anomalies near T_1 ~ 100-120 K and T_2 ~ 50-60 K, together with pronounced magnetic irreversibility, field-dependent hysteresis, and unsaturated magnetization. Increasing Cu concentration progressively suppresses the low-temperature magnetic state and weakens the field-induced moment. First-principles calculations favor Cu occupation at the square-planar sites, contrasting with the experimental refinements and highlighting strong competitions among local bonding, short-range disorder, and metastability in this highly frustrated quadruple perovskite system.
ER -