Observation of complete inversion of the hysteresis loop in a bimodal magnetic thin film

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 \mathrm{N}{\mathrm{i}}_{45}\mathrm{F}{\mathrm{e}}_{55}films with 1 to 2 nm thin \mathrm{N}{\mathrm{i}}_{3}\mathrm{Fe}secondary phases at the grain boundaries. The origin of the inverted loop,...