Faílde Daniel, Ocampo-Zalvide Victor, Serantes David, Iglesias Òscar
Applied Physics Department, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain.
Galicia Supercomputing Center (CESGA), Santiago de Compostela, Spain.
Nanoscale. 2024 Aug 7;16(30):14319-14329. doi: 10.1039/d4nr02045f.
Careful determination of the heating performance of magnetic nanoparticles under AC fields is critical for magnetic hyperthermia applications. However, most interpretations of experimental data are based on the uniaxial anisotropy approximation, which in the first instance can be correlated with the particle aspect ratio. This is to say, the intrinsic magnetocrystalline anisotropy is discarded, under the assumption that the shape contribution dominates. We show in this work that such a premise, generally valid for large field amplitudes, does not hold for describing hyperthermia experiments carried out under small field values. Specifically, given its relevance for applications, we focus our analysis on the so-called "Brezovich criterion", · = 4.85 × 10 A m s. By means of a computational model, we show that the intrinsic magnetocrystalline anisotropy plays a critical role in defining the heat output, determining also the role of the shape and aspect ratio of the particles on the SLP. Our results indicate that even small deviations from spherical shape have an important impact on optimizing the heating performance. The influence of interparticle interactions on the dissipated heat is also evaluated. Our results call, therefore, for an improvement in the theoretical models used to interpret magnetic hyperthermia performance.
精确测定交流磁场下磁性纳米颗粒的加热性能对于磁热疗应用至关重要。然而，大多数实验数据的解释基于单轴各向异性近似，首先这可以与颗粒的纵横比相关联。也就是说，在形状贡献占主导的假设下，本征磁晶各向异性被忽略了。我们在这项工作中表明，这样一个通常对大场振幅有效的前提，并不适用于描述在小场值下进行的热疗实验。具体而言，鉴于其对应用的相关性，我们将分析重点放在所谓的“布雷佐维奇准则”，即γ = 4.85 × 10⁻⁴ A m² s⁻¹。通过一个计算模型，我们表明本征磁晶各向异性在定义热输出方面起着关键作用，同时也确定了颗粒形状和纵横比对比吸收率（SLP）的作用。我们的结果表明，即使与球形有很小的偏差也会对优化加热性能产生重要影响。还评估了颗粒间相互作用对耗散热的影响。因此，我们的结果呼吁改进用于解释磁热疗性能的理论模型。
