Domain Wall Motion in Multilayered Magnetic Thin Films

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Abstract
In order to determine whether increased domain wall mobility is a possible explanation for the anomalously fast flux reversal observed in laminated films, the details of wall motion have been investigated for multilayer samples with from one to five 350‐Å Permalloy layers separated by 100‐Å layers of SiO, as well as for thick 1500‐Å films. Kerr effect quasistatic wall mobility measurements were made for the one‐ and two‐layer 350‐Å films and the 1500‐Å films, yielding mobilities of 9.2×103, 6.0×103, and 8.6×103 cm/sec·Oe, respectively. Bitter patterns were used to confirm the existence of Néel walls in the single‐layer 350‐Å films. The pulse conditions for these measurements produced locked Néel walls in the double films, as confirmed by Kerr effect observations. Bloch walls occur in the 1500‐Å films. Low‐drive domain‐wall‐motion flux‐reversal experiments were performed for all the laminated films, yielding Sw's of 1.9, 1.7, 1.9, 1.8, and 2.1 Oe·μsec, respectively. For linear switching curves the slopes (1/Sw) are taken to be proportional to the domain‐wall mobility. The measured mobilities for the single and double 350‐Å films and the 1500‐Å films do not differ significantly. The Sw values for all the laminated films are nearly equal. This mobility and switching data indicate that the anomalously fast flux reversal in laminated films can not be attributed to a mechanism involving domain wall motion.