Study on the Henkel plots applied to novel ferrite-based magnets

Henkel plot constitutes a classical experimental methodology to investigate the strength and/or nature of interparticle/intergranular interactions in magnets and nanomaterials [1,2]. This plot evaluates the differences between the isothermal remanence (IRM) and the DC demagnetization curve (DCD) that exhibit a linear relationship in the case of non-interaction conditions. Basing on the sign of the deviation from the linear relationship, positive or negative, magnetizing and demagnetizing interactions are postulated and often this is also correlated to the presence of exchange or dipolar interactions. In particular the plots are employed to investigate the coupling between the soft and the hard phases in novel spring-magnets. Recently hybrid Cobalt ferrite- CoFe nanostructures with enhanced remanence and apparent spring-magnet behaviour were reported even if different experiments demonstrate the absence of exchange coupling.