Magnetic hysteresis loss (iron loss) is an important magnetic property that determines the efficiency of electric motors and is therefore critical for electric vehicles. It occurs when the magnetic field within the motor core, made up of soft magnetic materials, is repeatedly reversed due to the changing flow of current in the windings. This reversal forces tiny magnetic regions called magnetic domains to repeatedly change their magnetization direction.

However, this change is not perfectly efficient and results in energy loss. In fact, iron loss accounts for approximately 30% of the total energy loss in motors, leading to the emission of carbon dioxide, which represents a pressing environmental concern.

Despite over half a century of research, the origin of iron loss in soft magnetic materials remains elusive. The energy spent during magnetization reversal in these materials depends on complex changes in magnetic domain structures. These have mainly been interpreted visually, and the underlying mechanisms have been discussed only qualitatively.

Lithium-ion batteries (LiBs) remain the most widely used rechargeable batteries worldwide, powering most portable and consumer electronics. LiBs are also used to power most electric and hybrid vehicles, which are predicted to become increasingly widespread over the next decades.

Despite their good performance and large-scale adoption, LiBs still primarily rely on cathode materials based on nickel (Ni) and cobalt (Co). Yet the processes required to source both these metals are known to be destructive for natural environments, while also leaving a high carbon footprint and requiring significant water.

Moreover, most of the cobalt used worldwide originates from the Democratic Republic of the Congo (DRC), where unsafe mining conditions and child labor are still common. Over the past decades, energy researchers have been trying to identify cathode materials that can be sourced safely and sustainably, while matching the performance of Ni and Co-based cathodes.