High-field recovery of the undistorted triangular lattice in the frustrated metamagnet CuFeO2

Pulsed field magnetization experiments extend the typical metamagnetic staircase of CuFeO2 up to 58 T to reveal an additional first order phase transition at high field for both the parallel and perpendicular field configuration. Virtually complete isotropic behavior is retrieved only above this transition, indicating the high-field recovery of the undistorted triangular lattice. A consistent phenomenological rationalization for the field dependence and metamagnetism crossover of the system is provided, demonstrating the importance of both spin-phonon coupling and a small field-dependent easy-axis anisotropy in accurately describing the magnetization process of CuFeO2.