Ferromagnetic materials for use with spin memory and logic devices include a geometry and composition adapted to increase spin injection efficiency and/or reduce fringe fields. The ferromagnetic materials can be oriented to implement a variable spin resistance. The ferromagnetic layers are fabricated to permit the device to have two stable magnetization states, parallel and antiparallel. In the "on" state the device has two settable, stable resistance states determined by the relative orientation of the magnetizations of the ferromagnetic layers. An external magnetic field can change the magnetization state of the device by orienting the magnetization of the ferromagnetic layers to be parallel or antiparallel, thus changing the resistance of the device to a current of spin polarized electrons.