Implementations described herein provide systems and methods for wireless charging. In one implementation, a portable electronic device comprises a housing, a planar inductor coil, and a ferromagnetic shield. The planar inductor coil is disposed in the housing and comprises a conductive wire wound a plurality of turns about a center point and in increasing radii. The ferromagnetic shield is disposed in the housing and overlaps the planar inductor coil. The ferromagnetic shield comprises a first layer comprising a first plurality of iron-based nanocrystalline ribbons arranged in adjacent rows along a first direction and a second layer comprising a second plurality of iron-based nanocrystalline ribbons overlapping the first layer. The second plurality of iron-based nanocrystalline ribbons is arranged in adjacent rows along a second direction different from the first direction.