Despite the absence of an apparent triangular pattern in the crystal structure, we observe unusually well pronounced 1/3 magnetization plateaus in the quasi one-dimensional Ising spin chain compound CoGeO3 which belongs to the class of pyroxene minerals. We succeeded in uncovering the detailed microscopic spin structure of the 1/3 magnetization plateau phase by means of neutron diffraction. We observed changes of the initial antiferromagnetic zero-field spin structure that are resembling a regular formation of antiferromagnetic "domain wall boundaries", resulting in a kind of modulated magnetic structure with 1/3-integer propagation vector. The net ferromagnetic moment emerges at these "domain walls" whereas two third of all antiferromagnetic chain alignments can be still preserved. We propose a microscopic model on the basis of an anisotropic frustrated square lattice to explain the observations.
@article{arxiv.2109.07367,
title = {Emergent 1/3 magnetization plateaus in pyroxene CoGeO$_3$},
author = {H. Guo and L. Zhao and M. Baenitz and X. Fabrèges and A. Gukasov and A. Melendez Sans and D. I. Khomskii and L. H. Tjeng and A. C. Komarek},
journal= {arXiv preprint arXiv:2109.07367},
year = {2021}
}