This study reports the prediction of half-metallicity in graphene nanoribbons (GNRs) using first-principles calculations. Half-metals are materials where electrical current can be completely spin-polarized due to the coexistence of metallic behavior for one spin orientation and insulating behavior for the opposite. The research demonstrates that applying in-plane homogeneous electric fields across the zigzag edges of GNRs can induce half-metallic behavior, with the magnetic properties controllable by these fields. The results have implications for spintronics, particularly at the nanoscale, based on graphene. Zigzag graphene nanoribbons (ZGNRs) have unique edge states that form a two-fold degenerate flat band at the Fermi energy. These edge states are localized and decay exponentially into the ribbon's center. The study shows that the ground state of ZGNRs has an antiferromagnetic spin configuration, with opposite spin orientations at the ribbon's edges. When external electric fields are applied, the spin states are affected, leading to a bandgap opening for one spin orientation while the other remains metallic. This results in a half-metallic state where one spin is insulating and the other is metallic. The half-metallic nature of ZGNRs is robust against edge defects, as shown by calculations for different types of defects. The critical electric field required for half-metallicity decreases with increasing ribbon width. The study also considers the effect of spin-orbit interactions, finding that they are too small to affect the half-metallic nature but may influence the spatial direction of spin up and down in the ZGNRs. The results suggest that ZGNRs can be used for spin-polarized current generation in nanoscale spintronic devices. The study provides a theoretical foundation for the potential of graphene-based nanoelectronics and highlights the importance of electric fields in controlling the magnetic properties of ZGNRs. The findings contribute to the understanding of the interplay between electric fields and electronic spin degrees of freedom in solids, and open new avenues for exploring spintronics at the nanoscale.This study reports the prediction of half-metallicity in graphene nanoribbons (GNRs) using first-principles calculations. Half-metals are materials where electrical current can be completely spin-polarized due to the coexistence of metallic behavior for one spin orientation and insulating behavior for the opposite. The research demonstrates that applying in-plane homogeneous electric fields across the zigzag edges of GNRs can induce half-metallic behavior, with the magnetic properties controllable by these fields. The results have implications for spintronics, particularly at the nanoscale, based on graphene. Zigzag graphene nanoribbons (ZGNRs) have unique edge states that form a two-fold degenerate flat band at the Fermi energy. These edge states are localized and decay exponentially into the ribbon's center. The study shows that the ground state of ZGNRs has an antiferromagnetic spin configuration, with opposite spin orientations at the ribbon's edges. When external electric fields are applied, the spin states are affected, leading to a bandgap opening for one spin orientation while the other remains metallic. This results in a half-metallic state where one spin is insulating and the other is metallic. The half-metallic nature of ZGNRs is robust against edge defects, as shown by calculations for different types of defects. The critical electric field required for half-metallicity decreases with increasing ribbon width. The study also considers the effect of spin-orbit interactions, finding that they are too small to affect the half-metallic nature but may influence the spatial direction of spin up and down in the ZGNRs. The results suggest that ZGNRs can be used for spin-polarized current generation in nanoscale spintronic devices. The study provides a theoretical foundation for the potential of graphene-based nanoelectronics and highlights the importance of electric fields in controlling the magnetic properties of ZGNRs. The findings contribute to the understanding of the interplay between electric fields and electronic spin degrees of freedom in solids, and open new avenues for exploring spintronics at the nanoscale.