A report of (topological) Hall anomaly two decades ago in Gd2PdSi3, and its relevance to the history of the field of Topological Hall Effect due to magnetic skyrmions

Abstract

The area of magnetic skyrmions, with potential revolution in certain applications, in condensed matter physics is considered about a decade old. In this article, we draw the attention of the community to the recent work of Kurumaji et al [Science 365, 914 (2019)] establishing magnetic skyrmion lattice behavior in Gd2PdSi3. We consider it important to bring out the two decades old history, in particular Hall transport anomalies characterizing magnetic skyrmions. The key experimental data in support of the skyrmion lattice that Kurumaji et al present is the observation of topological Hall resistivity in an intervening field range, following two metamagnetic transitions. In addition, the values are giant, compared to those known for other magnetic skyrmions. We point out here that such features in Hall resistivity data, arising from Gd 4f magnetism, can be found in our publication in 1999 (along with the metamagnetic transitions) and we expressed difficulties in explaining the results at that time. In view of above, we propose to the scientific community that the compound Gd2PdSi3, ex post facto, can be considered as the first experimental demonstration for giant topological Hall effect in this field, discovered about two decades ago. We take this opportunity to share some thoughts, offering clues for further investigations, in particular to identify novel magnetic skyrmions and to find the same to enable applications.