  On-chip magnets can be used to implement relatively large local magnetic
field gradients in na- noelectronic circuits. Such field gradients provide
possibilities for all-electrical control of electron spin-qubits where
important coupling constants depend crucially on the detailed field
distribution. We present a double quantum dot (QD) hybrid device laterally
defined in a GaAs / AlGaAs het- erostructure which incorporates two single
domain nanomagnets. They have appreciably different coercive fields which
allows us to realize four distinct configurations of the local inhomogeneous
field distribution. We perform dc transport spectroscopy in the Pauli-spin
blockade regime as well as electric-dipole-induced spin resonance (EDSR)
measurements to explore our hybrid nanodevice. Characterizing the two
nanomagnets we find excellent agreement with numerical simulations. By
comparing the EDSR measurements with a second double QD incorporating just one
nanomagnet we reveal an important advantage of having one magnet per QD: It
facilitates strong field gradients in each QD and allows to control the
electron spins individually for instance in an EDSR experi- ment. With just one
single domain nanomagnet and common QD geometries EDSR can likely be performed
only in one QD.
