Abstract: A method of manufacturing ion garnet layers having refractive indices n adjusted in a defined manner and lattice constants a.sub.o adjusted in a defined manner, in which the layers are deposited on a substrate by means of rf cathode sputtering using a target comprising substantially a garnet phase besides residual phases of substantially the same sputtering rates in a noble gas plasma of an ion energy of the ions bombarding the growing layer of smaller than 10.sup.2 eV and at a pressure in the range from 0.1 to 2.0 Pa, the noble gas being doped with up to 5% by volume of at least one reactive gas.