Precise adjustment of magnetic properties of bubble garnet wafers by etching

Abstract

Chemical etching in phosphoric acid was employed for postgrowth modification of magnetic bubble domain collapse field (H0) of epitaxially grown (YSmCa)a(FeGe)5012 magnetic garnet layers. The dependenee of the etching process on the etching conditions, the etching tate and the magnetic and surfaee features of the layers was investigated. Ir is possible to aehieve a pre-determined ehange in the eollapse field solely by controlling the etching time at a given temperature. For etching at 140 ~ the etehing rate is 3Ho/dt = (0.500 ~ 0.05) Oe ruin -1 for a decrease in thiekness 0.045 #m ruin -1. IntroduetionMagnetic garnet layers grown by the liquid phase epitaxial method have four properties that determine the applicability of the layers for bubble domain memories. For 5 #m domain applications the following values of these properties are required: thiekness: h = (5 ~ 0.5)/~m, collapse field of bubble domains: H 0 = (100 ~-1) Oe, period of stripe domains: Po = (10 • 1) #m, coercivity: He < 0.5 oe.One of the most important magnetie properties affecting the device performance is the collapse field, which must be controlled by the LPE growth process. However, experience shows that in epitaxial films this parameter varies from one layer to another, sometimes over a substantial range, even when the film growth conditions ate controlled to the utmost. The real values vary after growth for 90.2~ of our garnet films between 110 and 90 Oe. Modification is not possible when the collapse field is less than 100 Oe, but we were successfui in finding a technique for modification when 101 < H 0 < 110 Oe.Thermal annealing is one of those techniques in which the collapse field changes asa result of changing the saturation magnetization of the film. ~his method is not suitable, however, for films containing Ge 4+ ions, because of the hindered redistribution of Ge ~+ between tetrahedral and octahedral positions.Acta Physir ~4cademiae Sr