The use of perovskite manganite nanoparticles in magnetic hyperthermia has attracted significant attention due to their tunable magnetic properties and high specific absorption rate (SAR). In this work, we present a combined experimental and theoretical investigation of the frequency- and amplitude-dependent magnetic heating behavior of La_0.51Sr_0.49MnO₃ (LSMO) and Dy-doped La_0.51Dy_0.045Sr_0.445MnO₃ (DLSMO) nanoparticles. The nanoparticles were synthesized via the sol–gel method and characterized by XRD and SEM, while SAR values were experimentally evaluated under varying magnetic field strengths (60–120 Oe) and frequencies (150–300 kHz). In parallel, theoretical modeling based on Néel and Brownian relaxation mechanisms was employed to predict SAR behavior as a function of particle size, magnetic anisotropy, and fluid viscosity. The results reveal that Dy doping enhances magnetic anisotropy, which modifies the relaxation dynamics and leads to a reduction in SAR. The model identifies the optimal nanoparticle size (~18–20 nm) and ferrofluid viscosity to maximize heating efficiency. This combined approach provides a comprehensive framework for designing and optimizing perovskite-based nanoparticles for magnetic hyperthermia applications.

Magnetic hyperthermia is a medical technique based on the generation of therapeutic heat by a magnetic nanoparticle (MNP) system in the presence of a high-frequency electromagnetic field. The temperature developed in the tumoral tissue and the overall heating efficiency strongly depend on the magnetic field parameters (frequency and amplitude), as well as on the intrinsic properties of the MNPs. Nanoparticle clustering due to interparticle dipolar interactions plays an important role in the relaxation dynamics and significantly modifies the energy barriers involved in the Néel–Brown relaxation processes. In this work, the influence of interparticle spacing αnm, particle size dpnm, and crystalline anisotropy constant KJ/m3 on the Specific Absorption Rate (SAR) was analyzed using theoretical models that include dipolar interaction effects. Two relaxation scenarios were considered: the Dormann model, where the dipolar coupling increases the effective energy barrier, and the Mørup model, in which the effective barrier is reduced. The results reveal distinct behaviors of SAR: In the Dormann case SAR1, strong dipolar interactions within the cluster enhance the barrier and produce the maximum SAR for moderate α and K values, followed by a decrease toward a plateau at large interparticle distances. In contrast, the Mørup case SAR2 shows a monotonic increase in the SAR with particle dispersion, stabilizing when interparticle coupling becomes negligible. The optimal therapeutic range was found near dp≈17−18nm, where Néel relaxation is most efficient. Numerical simulation performed using COMSOL Multiphysics demonstrated that the spatial temperature distribution and the thermal damage of the tumoral tissue closely follow the SAR trends: Dormann-related heating Q1 produces higher local temperatures, while Mørup-related heating Q2 leads to smoother but less intense thermal profiles. In addition, the influence of carrier-fluid viscosity on the temperature rise is minimal, confirming the dominance of Néel relaxation in the investigated parameter range. These results show that controlling the particle arrangement, interparticle distance, and magnetic anisotropy enables tunable modulation of energy barriers and heating efficiency, providing valuable guidelines for optimizing nanoparticle-based agents in magnetic hyperthermia.

Magnetic hyperthermia is a promising therapeutic technique in which magnetic nanoparticles (MNPs) generate heat when exposed to a high-frequency alternating magnetic field. The magnetic dipolar interactions between magnetic nanoparticles play an important role in the relaxation dynamics and overall magnetic heating efficiency. In this work, the thermal response of a tumoral tissue was studied considering the dipole–dipole interactions in chain-like nanoparticle assemblies. A 3D space–time model implemented in COMSOL Multiphysics 6.2 is used to investigate the temperature field and thermal damage in tumoral tissue considering magnetic relaxation mechanisms for both (i) parallel and (ii) perpendicular anisotropy configurations with respect to the applied magnetic field. Dipole–dipole interactions significantly modify the effective energy barriers involved in magnetic relaxation mechanisms, when nanoparticles are closely spaced. Interparticle spacing and MNP size are two very important parameters that influence the effective anisotropy barrier and, implicitly, the heating efficiency of magnetic nanoparticles. Moderate dipolar interactions lead to optimal SAR values, while strong interactions reduce heating efficiency due to magnetic locking. This study provides guidelines for the design of magnetic nanoparticles for hyperthermia applications.