In search of a quantum phase transition between the two-dimensional (2D) ferromagnetism of CaCo2−yAs2 and stripe-type antiferromagnetism in SrCo2As2, we rather find evidence for 1D magnetic frustration between magnetic square Co layers. We present neutron diffraction data for Ca1−xSrxCo2−yAs2 that reveal a sequence of x-dependent magnetic transitions which involve different stacking of 2D ferromagnetically-aligned layers with different magnetic anisotropy. We explain the x-dependent changes to the magnetic order by utilizing classical analytical calculations of a 1D Heisenberg model where single-ion magnetic anisotropy and frustration of antiferromagnetic nearest- and next-nearest-layer exchange are all composition dependent.
@article{arxiv.1904.06444,
title = {Antiferromagnetic Stacking of Ferromagnetic Layers and Doping Controlled Phase Competition in Ca$_{1-x}$Sr$_{x}$Co$_{2-y}$As$_{2}$},
author = {Bing Li and Y. Sizyuk and N. S. Sangeetha and J. M. Wilde and P. Das and W. Tian and D. C. Johnston and A. I. Goldman and A. Kreyssig and P. P. Orth and R. J. McQueeney and B. G. Ueland},
journal= {arXiv preprint arXiv:1904.06444},
year = {2019}
}