Origin of recoil hysteresis loops in Sm–Co∕Fe exchange-spring magnets

Abstract

Open recoil loops are often interpreted as a consequence of a breakdown in exchange coupling and attributed to the decoupled soft phase in exchange-coupled permanent magnets. However, in element-specific recoil loop measurements on Sm–Co∕Fe exchange spring magnets, the authors found that the open recoil loops were present not only in the soft (Fe) layer but also in the hard (Sm–Co) layer, and were not a consequence of exchange coupling breakdown between the soft and hard layers. Comparison between the experimental results and micromagnetic calculations reveals that the observed open recoil loops originate from the anisotropy variations in the Sm–Co layer.