The realm of f-electron systems, encompassing materials with partially filled felectron shells, presents a captivating landscape for condensed matter physics due to the interplay of various interactions that govern their fascinating properties. These materials exhibit a rich tapestry of magnetic, electronic, and structural orders, often coexisting or competing with one another. Unveiling the theoretical underpinnings of these complex ordering phenomena is crucial for not only comprehending the fundamental physics at play but also for designing novel materials with tailored properties. One prominent theoretical approach to studying multiple ordering in f-electron systems is the use of Heisenberg models. These models capture the magnetic interactions between localized f-electrons via spin exchange terms. By incorporating additional interactions, such as crystal field anisotropy and exchange-striction effects, the model's Hamiltonian can be tailored to represent specific f-electron materials. Diagonalization techniques or Monte Carlo simulations are then employed to solve the model and determine the ground state and low-energy excitations, revealing the nature of the magnetic order that emerges. Another powerful theoretical framework is the coherent potential approximation (CPA).