纳米Dy_(0.15)Fe_(1.85)O_3磁颗粒的低温磁特性研究

Study on Magnetic Properties of Dy_(0.15)Fe_(1.85)O_3 Magnetic Nanoparticles at Low Temperature

采用共沉淀–相转化法制备了纳米Dy0.15Fe1.85O3磁颗粒,研究了低温条件下温度变化对其磁学特性的影响.采用XRF、TEM、XRD和超导量子磁强计(SQUID)对样品的化学成份、形貌、晶型结构和磁学性能进行了表征.结果表明:样品中的金属离子主要是Dy3+、Fe3+,含量分别为12.17wt%、51.88wt%.形貌为类球形,平均粒径约15 nm,且结晶性完全,晶型为面心立方尖晶石结构.在56.5～200.2 K范围内,样品的饱和磁化强度(MS)、矫顽力(HC)均随温度的降低呈现出增大的变化规律,当温度T≥142.8 K时,呈超顺磁性状态;当T<142.8 K时,由超顺磁性状态转化为铁磁性状态.

Dy0.15Fe1.85O3 magnetic nanoparticles were prepared by coprecipitation-phase transfer method, and the effect of temperature variation on the magnetic properties of the nanoparticles at low temperature were investigated. The chemical composition, morphology, crystalline structure and magnetic properties of the samples at low tem- perature were characterized by X-ray fluorescence spectrometer（XRF）, transmission electron microscope （TEM）, X-ray diffraction （XRD） and super-conducting quantum magnetometer （SQUID）. The results show that metal ions in the sample are mainly Dy3＋ and Fe3＋ whose mass fractions are 12.17% and 51.88%, respectively. The average diameter of the samples is ca. 15 nm. The magnetic particles are spherical with face-centered cubic spinel structure and complete crystalline. The saturation magnetization （Ms） and coercivity （Hc） of the samples increase with the decrease of temperature in the range of 56.5 K and 200.2 K. When the temperature exceeds or is equal to 142.8 K, the magnetic properties of the samples is at the superparamagnetic state. While the temperature is below 142.8 K, the superparamagnetic state is converted to ferromagnetic state.