As discussed in this chapter, we develop a mean-field mathematical method to calculate the ground states of antiferromagnets and better understand the applied magnetic-field induced exotic properties. Within antiferromagnetic materials competitive and cooperative interactions exist leading to substance extraordinary magnetic states. Our calculations predict that applying a magnetic field to antiferromagnets can switch it from one magnetic state to another. These include antiferromagnetic ground state, spin-flop transition, spin-flopped state, spin-flip transition and spin-flipped state. Our framework successfully demonstrates these phase changes. With this, a map of all equilibrium magnetic ground states, as well as the respective equilibriumphase conditions, are derived. Our study provides insight into the origins of the various magnetic states.