Abstract
The existence of inverted hysteresis loops (IHLs) in magnetic materials is still in debate due to the lack of direct evidence and convincing theoretical explanations. Here we report the direct observation and physical interpretation of complete IHL in films with 1 to 2 nm thin secondary phases at the grain boundaries. The origin of the inverted loop, however, is shown to be due to the exchange bias coupling between and , which can be broken by the application of a high magnetic field. A large positive exchange bias is observed in the NiFe composite material giving novel insight into the formation of a noninverted hysteresis loop (non-IHL) and IHL, which depend on the loop tracing field range (). The crossover from non-IHL to IHL is found to be at 688 Oe.
- Received 19 August 2016
- Revised 1 February 2017
DOI:https://doi.org/10.1103/PhysRevB.95.100401
©2017 American Physical Society