The dimensionality of the electronic and magnetic structure of a given material is generally predetermined by its crystal structure. Here, using elastic and inelastic neutron scattering combined with magnetization measurements, we find unusual magnetic behavior in three-dimensional (3D) Ba2CoO4. In spite of isolated CoO4 tetrahedra, the system exhibits a 3D noncollinear antiferromagnetic order in the ground state with an anomalously large Curie-Weiss temperature of 110 K compared to TN = 26 K. More unexpectedly, spin dynamics displays quasi-2D spin wave dispersion with an unusually large spin gap, and 1D magnetoelastic coupling. Our results indicate that Ba2CoO4 is a unique system for exploring the interplay between isolated polyhedra, low-dimensional magnetism, and novel spin states in oxides.
@article{arxiv.1903.02490,
title = {Anomalous Magnetic Behavior in Ba2CoO4 with Isolated CoO4 Tetrahedra},
author = {Qiang Zhang and Guixin Cao and Feng Ye and Huibo Cao and Masaaki Matsuda and D. A. Tennant and Songxue Chi and S. E. Nagler and W. A. Shelton and Rongying Jin and E. W. Plummer and Jiandi Zhang},
journal= {arXiv preprint arXiv:1903.02490},
year = {2019}
}