Tuning between composition and nanoparticle size of manganites for self-regulated magnetic hyperthermia applications

Abstract

Abstract Self-regulated magnetic hyperthermia is a promising alternative for cancer treatment based on tumor annihilation by heating using appropriate Curie temperature ( T C ) as an internal temperature controller. We successfully prepared strontium-doped lanthanum manganite nanoparticles (LSMO-x) using the sol-gel method. The T C can be adjusted by modifying both the composition and diameter of the particles, that is, varying the Sr content (0.2  ⩽ x ⩽  0.3) and the annealing temperature (600 ∘C, 700 ∘C, and 800 ∘C). Structural, morphological, chemical, and magnetic properties were investigated. The samples exhibit the structure of perovskites with average particle sizes ranging from 17 nm to 27 nm, depending on the annealing temperature. This diameter range ensures that all samples investigated are have negligible remanence at room temperature. Magnetization studies show that T C increases as Sr content and particle size increase, indicating that the T C is governed by both. Thus T C can be adjusted by combining these two parameters for self-regulated magnetic hyperthermia. Magnetic hyperthermia measurements showed that samples with larger particle sizes ( ⩾ 19 nm) were more efficient in promoting heat, that is, presenting a higher specific absorption rate (SAR), probably due to the adequate balance between the Néel and Brownian relaxations behavior. We figure out that the SAR value is essential for this specific finality, but it should also consider the maximum temperature reached during the hyperthermia essays. Finally, we build up a nanoparticle diameter vs. Sr concentration phase diagram, where the SAR values are displayed, which allows for predicting the best sample for the self-regulated hyperthermia.