Moreover, the effective anisotropy constant (Keff) of the different MNP@PMAO serie was estimated from the formula 𝐾𝐾𝐾𝐾𝐴𝐴𝐴𝐴 = 𝑀𝑀𝑀𝑀 * 𝐻𝐻𝐻𝐻 2 , MS and HK being measured at 5 K following Stoner and Wohlfarth model . The obtained values (Table ) confirmed a decrease in Keff from 3.9 to 2.7 x 10 5 J/m 3 as Mn 2+ content increased up to xEmpiric = 0.60 and an increase for samples with x ≥ 0.60, confirming the direct correlation between HC and Mn 2+ content. It is noticeable that Keff for Mn0.60Fe2.40O4 is close to the values reported for MnFe2O4 MNPs (1-2 × 10 5 J/m 3 ) , which highlights the increasing impact of Mn 2+ content on the effective anisotropy of the samples. Aiming to compare both methods, we selected very near low frequencies, 155 kHz for the calorimetric method and 150 kHz for AC magnetometry at a fixed H of 16.8 kA/m. Considering our best nanoheater