Computationally Modeling the Magnetization of Ca­­₃Co₂O₆

Magnetic materials play integral roles in emerging technologies including sensors and spintronic devices used in quantum computing. Understanding the thermodynamic properties of magnetic materials is essential to enabling technological advancements. The phase diagram of Ca­­₃Co₂O₆ exhibits several regions of nontrivial competition between nearly-degenerate magnetic orders. This is a consequence of Co₂O₆ chains forming a triangular lattice with ferromagnetic intrachain and antiferromagnetic interchain interactions and two distinct cobalt sites with different local symmetry. The goal of this research project was to investigate the magnetic phase diagram of Ca­­₃Co₂O₆ by modeling its magnetization, and the magnetic plateaus that are present, with Monte Carlo simulations. Ca­­₃Co₂O₆ is reduced to a two-dimensional triangular lattice by representing each chain as a rigid spin with antiferromagnetic Ising interactions since the ferromagnetic intrachain interactions are much stronger than interchain interactions. A random-exchange term was also included to account for defects and inhomogeneities. Including a random-exchange term quantitatively improved agreement with measured magnetization data by rounding magnetic steps. The simulated magnetic phase boundaries quantitatively disagreed with published phase diagrams. This discrepancy is likely caused by representing the chains as rigid spins, which oversimplifies the complex inter and intrachain interactions.