Observation of domain expansion and contraction in TbFe films by Lorentz microscopy

Lorentz electron microscopy techniques have been used to study in situ, at room temperature, the expansion and contraction of thermomagnetically written circular domains in Tb₁₉Fe₈₁ and Tb₃₂Fe₆₈ films. Domains expand or contract more or less radially in Tb₁₉Fe₈₁, but with the development of jagged walls. In Tb₃₂Fe₆₈, dendritelike stripe domains with jagged walls form either outside or within the existing domains, leaving the perimeter of the initial circular domains unchanged. The difference in behavior can be understood in terms of the difference in the importance of the local demagnetizing field relative to the local total field. The implications of the nonuniform wall motion for the appearance of domain irregularity during thermomagnetic recording are discussed