The etch rate of material due to ion bombardment is the amount of material removed per unit time at a given set of beam parameters. Usually the etch rate is given in units of length/time. The length is measured as the depth of the craters formed by the ion/laser beam. With insulating materials a dependence was obtained of the etch rate on charging effects. Crater formation is also influenced by charging, i.e. ‘walls’ are built around the craters. These effects were studied in different oxidic materials, (yttrium-iron-garnets (YIG) and gadolinium-gallium-garnets (GGG)).