BaFe $_{12-x}$ Ga $_x$ O $_{19}$纳米粒子中的Hopkinson峰和超顺磁效应
Hopkinson peak and superparamagnetic effects in BaFe$_{12-x}$Ga$_x$O$_{19}$ nanoparticles
摘要：
本文研究了用球磨法制备的Ga取代钡铁氧体纳米粒子的热磁性能。样品的热磁曲线与x范围从0.0到1.0表现出尖锐的峰值与高磁化强度低于TC（霍普金森峰）。我们样品的峰高与先前观察到的或计算的值相似或更高。对实验数据的理论处理表明，这些峰是由于磁性粒子的超顺磁弛豫效应。这种效果被证实的滞后测量，并刚刚低于峰值发生的温度。因此，使用基于单轴、随机取向、单畴、非相互作用颗粒系统的超顺磁性行为的理论模型，从实验数据计算颗粒直径。11 - 26 nm的计算直径小于由TEM测量确定的物理直径。对计算值偏低的原因进行了讨论。
英文摘要：
In this article, the thermomagnetic properties of a system of Ga-substituted barium hexaferrite nanoparticles ( ) prepared by ball milling were investigated. The thermomagnetic curves for the samples with x ranging from 0.0 to 1.0 exhibited sharp peaks with high magnetization just below TC (Hopkinson peaks). The height of the peak for our samples was similar or larger than previously observed or calculated values. Theoretical treatment of the experimental data demonstrated that the peaks are due to the effect of superparamagnetic relaxations of the magnetic particle. This effect was confirmed by hysteresis measurements at, and just below the temperature at which the peak occurred. Consequently, the particle diameters were calculated from the experimental data using a theoretical model based on the superparamagnetic behavior of a system of uniaxial, randomly oriented, single domain, non-interacting particles. The calculated diameters of 11 - 26 nm are less than the physical diameters determined from TEM measurements. The factors responsible for the low calculated values are discussed.
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