Hidden symmetries and gyromagnetic ratio of Kerr–Newman black holes in f(R) gravity

In this paper, we explore hidden symmetries in electrically charged, four-dimensional rotating Kerr–Newman black hole within [Formula: see text] gravity. By deriving the Killing and Killing-Yano tensors, we establish their role in the spacetime structure. The gyromagnetic ratio is calculated and shown to retain its universal value of [Formula: see text], consistent with all four-dimensional black holes. These findings show that the gyromagnetic ratio remains consistent in this modified gravity setting. Moreover, they highlight the connection between hidden symmetries and the ability to separate the Hamilton–Jacobi equation in [Formula: see text] gravity. This work advances the study of black holes in modified gravity, offering implications for both theoretical frameworks and observational cosmology such as gravitational wave analyses.