  Accurate knowledge of the heating performance of magnetic nanoparticles
(MNPs) under AC fields is critical for the development of hyperthermia-mediated
applications. Usually reported in terms of the specific loss power (SLP)
obtained from the temperature variation ($\Delta{T}$) vs. time (t) curve, such
estimate is subjected to a huge uncertainty. Thus, very different SLP values
are reported for the same particles when measured on different
equipment/laboratories. This lack of control clearly hampers the further
development of MNP-mediated heat-triggered technologies. Here we report a
device-independent approach to calculate the SLP value of a suspension of MNPs:
the SLP is obtained from the analysis of the peak at the field on/off switch of
the $\Delta{T}(t)$ curve. The measurement procedure, which itself constitutes a
change of paradigm within the field, is based on fundamental physics
considerations: specifically to guarantee the applicability of Newton's law of
cooling, as i) it corresponds to the ideal scenario in which the temperature
profiles of the system during heating and cooling are the same; and ii) it
diminishes the role of coexistence of various heat dissipation channels. Such
an approach is supported by theoretical and computational calculations to
increase the reliability and reproducibility of SLP determination. This is
experimentally confirmed, demonstrating a reduction in SLP variation across 3
different devices located in 3 different laboratories. Furthermore, the
application of this peak analysis method (PAM) to a rapid succession of field
on/off switches that result in a zigzag-like $\Delta{T}(t)$, which we term the
zigzag protocol, allows evaluating possible variations of the SLP values with
time or temperature.
