Mechanisms of AC losses in magnetic fluids based on substituted manganites

Abstract

The ability to controllably tune the heating efficiency of magnetic nanoparticles in an AC magnetic field is highly desirable for their application as mediators of magnetic hyperthermia. Traditional approaches to understand and govern the behavior of hyperthermia mediators include a combination of quasistatic and high-frequency (∼100 kHz) magnetic measurements with subsequent simulation of underlying processes. In this paper, we draw attention to the frequently overlooked fact that for an ensemble of magnetic nanoparticles, there is no straightforward complementarity between the dynamic characteristics obtained under different experimental conditions, as well as between corresponding underlying processes. This paper analyzes mechanisms of AC losses in a fluid based on magnetic nanoparticles, with special emphasis on the domains of their validity, and shows that the mechanisms may become qualitatively different as experimental conditions change from magnetostatic to high-frequency ones. Further, the work highlights new important features which can result from the employment of the refined approaches to interpret experimental results obtained on magnetic fluids based on La1-xSrxMnO3 (x = 0.22) nanoparticles. The gained knowledge provides necessary guidelines for tailoring the properties of magnetic nanoparticles to the needs of self-controlled magnetic hyperthermia.

Effect of Synthesis Temperature on Structure and Magnetic Properties of (La,Nd)0.7Sr0.3MnO3 Nanoparticles

“…It is shown in [36, 37] that the temperature behavior of particle ensembles can be satisfactory as described by the average Curie temperature concept. In this case, it is expected that the behavior of the ensembles’ magnetization will obey the law M(T) .…”

Iron-Doped (La,Sr)MnO3 Manganites as Promising Mediators of Self-Controlled Magnetic Nanohyperthermia

“…Many scientific papers have stressed high potential of their application in different fields of science and technology [1–3]. One of the most promising directions of magnetic nanoparticle investigations is the opportunity to use them in engineering, medicine, and biology, particularly for creation of new magnetic recording systems, for biological fluid purification, for drug and gene delivery, and for hyperthermia [4–6].…”

“…To be applicable as mediators of nanohyperthermia, the nanoparticles have to satisfy a number of requirements: they have to be single domain, weakly agglomerated, and small in size and display superparamagnetic properties [6]. In addition, they have to demonstrate high heating efficiency under an alternating magnetic field to be able to heat the tumor area to 42–45 °C (optimal for destroying the tumors) [3, 8]. …”

“…One more essential drawback of magnetite is the fact that the transition temperature from magnetically ordered to non-magnetic state (Curie temperature) is quite high: T C  = 585 °C [11]. Since magnetic-field-induced heating is only operative in magnetically ordered state [3], high Curie temperature may give rise to uncontrolled and non-uniform heating of tumors to high temperatures, which, in turn, may lead to destroying the healthy tissues.…”

Synthesis, Properties and Applications of some Magnetic Oxide Based Nanoparticles and Films

“…According to theoretical estimations [15], the heating efficiency of magnetic nanoparticles may be significantly enhanced by finding ways to shift T b close to room temperature. In this case, the mechanism of high-frequency losses transforms from the Néel-Brown relaxation to the StonerWohlfarth-model-based remagnetization, which results in the strong increase of AC energy dissipation [15]. These data were taken into account for the development of magnetic nanoparticles, which may be used in medicine, particularly in hyperthermia treatment.…”