Research on nanoscopic magnet including 3d transition metals

研究了含3d过渡金属纳米粒子的磁性。制备的样品为Co 3 O 4、Mn 3 O 4、Mn 2 O3、Ni铁氧体、NiZn铁氧体、Mn铁氧体、Mg铁氧体和无定形SiO2。1.尺寸为3 nm的Co 3 O 4纳米颗粒在阻断温度Tb以下表现出铁磁性，而块体晶体在TN=33 K以下表现出反铁磁性。对于2.5 nm-样品被认为是有序的周期性比其他样品，虽然尺寸非常小。XAFS的测量结果证实了这一现象。3.在空气中，Ni（OH）_2单层纳米团簇在973 K以上退火制备了NiO纳米颗粒。在磁化强度测试中观察到了超顺磁性或铁磁性，证实了NiO纳米粒子的特征性质。4.制备了无定形SiO2包裹的Ni 1-xZnFe_2 O_4（2<x<1）混合铁氧体纳米粒子。通过热处理将颗粒尺寸控制在2.6 nm至33.7 nm的范围内，并研究了x=0.5区域的饱和磁化强度Ms的颗粒尺寸依赖性。颗粒大小的Ms值突然下降。饱和磁化强度Ms与Zn含量的关系与Ni-Zn铁氧体块体晶体的饱和磁化强度关系基本相似，但Ms的绝对值比块体晶体的Ms的绝对值小30%左右。医学应用功能化是新出现的。

Magnetic properties of nanoparticles including 3d transition metals were investigated. Prepared samples were Co3O4, Mn3O4,Mn2O3, Ni-ferrite, NiZn-ferrite, Mn-ferrite, Mg-ferrite surrounded by amorphous SiO2.1.Co3O4 nanoaprticles with 3 nm in size showed ferromagnetic behavior below blocking temperature Tb, though bulk crystal has antiferromagnetic below TN=33 K.2.Magnetization of Mn3O4 nanoparticles showed drastic change depending on particle sizes. For 2.5 nm- sample was considered to be ordered periodically than other samples though the size was extremely small. This phenomenon could be confirmed by the results of XAFS measurements.3.NiO nanoparticles were produced by annealing Ni(OH)2 monolayer-nanoclusters above 973 K in air. In the magnetization measurements superparamagnetic or ferromagnetic behaviors were observed and characteristic properties of NiO nanoparticles were confirmed.4.Nil-xZnFe2O4(2<x<1) mixed ferrite nanoparticles encapsulated with amorphous SiO2 were prepared. Particle sizes were controlled to range from 2.6 nm to 33.7 nm by heat treatment, and the particle size dependence of saturation magnetization Ms was investigated for the x=0.5 region. The Ms value decreased abruptly for particle sizes. The relationship between saturation magnetizations Ms and the Zn concentration was almost similar to that between the saturation magnetization and Ni-Zn ferrite bulk crystal, however, the absolute values of Ms of the nanoparticles were about 30 % smaller than those of bulk crystal5.XAFS measurements and thermal analysis were also performed for all the samples. Functionalizing of medical application was newly considerd.