  We present a method for efficient spin wave guiding within the magnonic
nanostructures. Our technique is based on the anomalous refraction in the
metamaterial flat slab. The gradual change of the material parameters
(saturation magnetization or magnetic anisotropy) across the slab allows
tilting the wavefronts of the transmitted spin waves and controlling the
refraction. Numerical studies of the spin wave refraction are preceded by the
analytical calculations of the phase shift acquired by the spin wave due to the
change of material parameters in a confined area. We demonstrate that our
findings can be used to guide the spin waves smoothly in curved waveguides,
even through sharp bends, without reflection and scattering between different
waveguide's modes, preserving the phase -- the quantity essential for wave
computing.
