We report a study of the Ca0.73La0.27FeAs2 single crystals. We unravel a monoclinic to triclinic phase transition at 58 K, and a paramagnetic to stripe antiferromagnetic (AFM) phase transition at 54 K, below which spins order 45∘ away from the stripe direction. Furthermore, we demonstrate this material is substantially structurally untwinned at ambient pressure with the formation of spin rotation walls (S-walls). Finally, in addition to the central-hole and corner-electron Fermi pockets usually appearing in Fe pnictide superconductors, angle-resolved photoemission (ARPES) measurements resolve a Fermiology where an extra electron pocket of mainly As chain character exists at the Brillouin zone edge.
@article{arxiv.1505.05881,
title = {Structural and magnetic phase transitions in Ca$_{0.73}$La$_{0.27}$FeAs$_2$ with electron overdoped FeAs layers},
author = {Shan Jiang and Chang Liu and Huibo Cao and Turan Birol and Jared M. Allred and Wei Tian and Lian Liu and Kyuil Cho and Matthew J. Krogstad and Jie Ma and Keith M. Taddei and Makariy A. Tanatar and Moritz Hoesch and Ruslan Prozorov and Stephan Rosenkranz and Yasutomo J. Uemura and Gabriel Kotliar and Ni Ni},
journal= {arXiv preprint arXiv:1505.05881},
year = {2016}
}