  Strong, adjustable magnetic couplings are of great importance to all devices
based on magnetic materials. Controlling the coupling between adjacent regions
of a single magnetic layer, however, is challenging. In this work, we
demonstrate strong exchange-based coupling between arbitrarily shaped regions
of a single ferrimagnetic layer. This is achieved by spatially patterning the
compensation temperature of the ferrimagnet by either oxidation or He+
irradiation. The coupling originates at the lateral interface between regions
with different compensation temperature and scales inversely with their width.
We show that this coupling generates large lateral exchange coupling fields and
we demonstrate its application to control the switching of magnetically
compensated dots with an electric current.
