Magnetic domain studies in gadolinium

Abstract

The domain structure of gadolinium has been observed and investigated. The wet colloid techniquehas been used f o r observation at temperatures down to 240K. The dry colloid technique has been used forthe observation of the patterns formed at low temperatures below 240K. Various specimens of gadoliniumof different sizes have been used to investigate the changes of domain structure with crystal shape andsize. All the crystals except one were obtained from the Centre for Materials Science University of Birmingham,and were high purity. At 273K patterns on planes containing the c-axis showed parallel l80 walls, with the development o f reverse domains. The effect of the crystal thickness on the size of the domain structure has been observedon the basal plane at 273K. This is discussed and found to agree with an. expression due to Kaczer. The effect on the patterns of reducing the temperature has been studied. The domain structure has been observed at 77K, where the easy directions lie on a cone around the c-axis, on all prepared surfaces. The zero field basal plane pattern shows complex wall structure, while planes containing the c-axis show a system of domains parallel to the c-axis. The effect of applying a magnetic field on the domain structure has been observed and is discussed. The lengths of daggers of reverse magnetization and the widths of their bases were found to be in direct proportion at both temperatures 77K and 216k.An interpretation of the pattern Is given for the two range of temperature, where the c-axis is easy and for the easy cone region. A model is given for the patterns observed at 77K and its limitations discussed. Possible types of walls and magnetization direction are also discussed on the basis of the known magnetic properties of the material.