  Spin-wave based transmission and processing of information is a promising
emerging nano-technology that can help overcome limitations of traditional
electronics based on the transfer of electrical charge. Among the most
important challenges for this technology is the implementation of spin-wave
devices that can operate without the need for an external bias magnetic field.
Here we experimentally demonstrate that this can be achieved using
sub-micrometer wide spin-wave waveguides fabricated from ultrathin films of
low-loss magnetic insulator - Yttrium Iron Garnet (YIG). We show that these
waveguides exhibit a highly stable single-domain static magnetic configuration
at zero field and support long-range propagation of spin waves with gigahertz
frequencies. The experimental results are supported by micromagnetic
simulations, which additionally provide information for optimization of
zero-field guiding structures. Our findings create the basis for the
development of energy-efficient zero-field spin-wave devices and circuits.
