Six magnetization plateau phases in a kagome antiferromagnet with Y₃Cu₉(OH)₁₉Cl₈-type distortion

A recently discovered kagome antiferromagnet Y₃Cu₉(OH)₁₉Cl₈ has attracted significant interest due to its unique kagome lattice structure and magnetic properties. Two separate studies have proposed distinct sets of exchange interaction parameters for this compound. In this study, we investigate the ground state of the spin-1/2 Heisenberg kagome model with three types of nearest-neighbor exchange interactions under a magnetic field by exact diagonalization using the Lanczos method. We reveal that clear magnetization plateaus at M/Mₛₐₜ=1/3, 5/9, and 7/9 are present under both parameter sets, which are identified as magnon crystal states based on their spin structures. Our findings suggest that these plateaus could potentially be experimentally confirmed with magnetization measurements on Y₃Cu₉(OH)₁₉Cl₈ under a magnetic field of approximately 300 T. Due to the uncertainty in the exchange interactions of Y₃Cu₉(OH)₁₉Cl₈, we perform additional calculations by varying these interactions. Consequently, we discover additional plateau phases at M/Mₛₐₜ=1/3, 5/9, and 7/9, each distinctly different from the magnon crystal states.