A planar magnetic core includes multiple ferromagnetic layers including multiple hard ferromagnetic bias layers and multiple soft ferromagnetic layers. Each ferromagnetic layer comprises a soft ferromagnetic layer or a hard ferromagnetic bias layer. Each hard ferromagnetic bias layer is a neighboring ferromagnetic layer of at least one soft ferromagnetic layer. The planar magnetic core also includes a plurality of insulating layers, each insulating layer disposed between adjacent ferromagnetic layers. Each ferromagnetic layer has an easy axis of magnetization parallel to a principal plane of the planar magnetic core, where the easy axes of magnetization are aligned. Each hard ferromagnetic bias layer is magnetized to create an in-plane bias magnetic flux through the hard ferromagnetic bias layer in a first direction that is parallel to the easy axis of magnetization and forms a closed path through a neighboring soft ferromagnetic layer in a second direction parallel to the first direction.