Ferromagnetic properties of Cu- and Fe-codoped nanocrystalline CdO powders: Annealing in hydrogen promote long-range ferromagnetic order

A mixture of cadmium acetate dihydrate, bis(acetylacetonato)copper, and tris(acetylacetonato)iron complexes is thermally co-decomposition to synthesizes Cu and Fe-codoped CdO (CdO:Cu:Fe) powders. The aim of this study is to examine the effect Fe doping on the appearance and development of room temperature ferromagnetism (RT-FM) in the presence of Cu ions as catalyst. X-ray diffraction (XRD) and X-ray fluorescence (XRF) measurements were carried out to study powders purity and crystalline structure. The XRD results show that Cu and Fe ions are incorporated in the ZnO crystal lattice by occupying Zn sites thereby forming ZnO:Cu:Fe solid solution (SS), whereas XRF confirms the purity of the obtained SS. The magnetic properties of the as-prepared and H-annealed (CdO:Cu:Fe–H) SS powders was investigated as a function of %Fe doping level. It was observed that the magnetic behaviour of pure as-synthesised CdO is mainly diamagnetic with slight FM phase. However, its behaviour with Cu and Fe codoping transforms to the mostly paramagnetic overlapped with small FM behaviour. More importantly, it was found that that annealing under H₂ atmosphere induces the reduction of CdO to form pure Cd metal, resulting in total transformation to FM behaviour with strength increases consistently with doping. Furthermore, with hydrogenation a tremendous enhancement of FM parameters takes place so that the M_s increases by about 1230% reaching a very high value of 1.43 emu/g for 1.8%Fe doping level of CdO.     

Room Temperature Ferromagnetismin Co-doped ZnO Bulks

Pure single phase of Zn0.95Co0.05O bulks were successfully prepared by solidstate reaction method.The effects of annealing atmosphere and temperature on the room temperature ferromagnetic behavior were investigated. The results show that the airannealed samples has similar weak ferromagnetic behavior with the assintered samples, but the obvious ferromagnetic behavior is observed for the samples annealed in vacuum or Ar/H2 gas, indicating that the strong ferromagnetism is associated with high oxygen vacancies density. High saturation magnetization Ms=0.73 μB/Co and eoercivity Hc=233.8Oe are obtained for the Ar/H2 annealed samples with pure single phase structure when annealing temperature is 600 ℃.     

二维Fe5GeTe2单晶的大量制备及吸波性能研究

目的 快速制备克量级、高质量的二维磁性Fe₅GeTe₂单晶，并开发具有范德华结构、室温铁磁性及优异微波吸收性能的新型吸波材料。方法 通过调控输运剂的含量，并缩短化学气相传输法的恒温段时长，以探索高质量Fe₅GeTe₂单晶的快速、制备量大的方法。将Fe₅GeTe₂单晶与石蜡按不同质量分数混合后，通过同轴线测试法分析其微波性能。结果 成功制备了克量级、高质量的Fe₅GeTe₂单晶样品。借助矢量分析仪的同轴线测试法研究Fe₅GeTe₂单晶的微波损耗性能发现，当Fe₅GeTe₂的质量分数为30%时，Fe₅GeTe₂的吸波特性较差，最佳反射损耗值仅为-4.8dB；当Fe₅GeTe₂的质量分数达到70%时，Fe₅GeTe_...     

On the possibility of ferromagnetism in CdO:Mn at room temperature

Nanocrystalline samples of Cd_{1? x} Mn _x O (x?=?0.00, 0.02, 0.04 and 0.06) were synthesised by sol–gel method and characterised by X-ray diffraction, Faraday's rotation, Guoy's method and electron paramagnetic resonance (EPR) at room temperature (RT). Results reveal that ferromagnetism at RT for Mn-doped CdO nanoparticles is possible.     

铬掺杂CdS纳米棒室温铁磁性及光学性质

具有室温铁磁性能的Cr掺杂CdS纳米棒用简单的溶剂热法被成功地合成。X-射线衍射(XRD)分析表明产物为六方相CdS。 透射电镜(TEM)分析表明,不同铬含量的CdS均为纳米棒,CdS纳米棒长为100-350 nm,平均直径为20-30 nm,几乎与掺入铬的质量无关。 能量色散谱(EDS)测试表明,合成产物由S、Cd和Cr组成。振动样品磁强计(VSM)表明,Cr掺杂CdS纳米棒在室温下具有铁磁性,而没有Cr掺杂CdS纳米棒具有弱铁磁性。Cr掺杂CdS纳米棒(Cr = 4.17 at%,7.31 at%)的饱和磁化强度Ms分别约为3.907和8.798(10-3 emu/g),Hc的矫顽力约为96.21和 137.15 Oe。 CdS纳米棒室温铁磁性能的产生与CdS晶格中Cd原子被Cr的取代有着密切关系。     

注入剂量对300℃下Mn+注入p型GaN薄膜的结构和磁性影响

在(0001)面的蓝宝石衬底上用低压MOCVD法生长p型GaN外延层.对p型GaN薄膜用180keV的Mn 离子注入进行磁性粒子掺杂,注入时GaN薄膜处于300℃,注入剂量分别为5.0×1015、1.0×1016和5.0×1016cm-2.对注入的样品在N2气流中进行快速热退火处理,温度为850℃,时间为30s.用超导量子干涉仪(SQUID)对样品的磁性进行了分析,在5.0×1015cm-2的注入样品中发现了较强的铁磁性;而1.0×1016和5.0×1016cm-2的Mn 离子注入样品中铁磁响应有所减弱.结合用X射线衍射(XRD)和扫描电子显微镜(SEM)对在不同剂量下Mn 注入GaN薄膜的结构、形貌和成分的分析,揭示了不同剂量磁性离子注入给GaN薄膜带来的结构、形貌和相应的铁磁性变化规律,发现只有适当的注入剂量(5.0×1015cm-2)才有利于在300℃下用180keV的Mn 注入对p型GaN薄膜进行磁性离子掺杂.     

Zn_(1-x)Mn_xS稀磁半导体的水热法制备及其性能

以乙二胺为修饰剂,采用水热法合成了不同掺杂比例的Zn_(1-x)Mn_xS(x=0,0.02,0.05,0.07)稀磁半导体材料,并通过XRD、FESEM、HRTEM、XEDS、光致发光光谱(PL)和振动样品磁强计(VSM)对样品的晶体结构、形貌、光学性能和磁学性能进行表征。实验结果表明:本方法制备的所有样品具有结晶良好的纤锌矿结构,没有杂峰出现;样品形貌为一维的纳米棒状,分散性良好;掺杂的Mn2+以替代Zn2+的形式进入到ZnS晶格中,随着Mn掺杂量的增加晶格常数呈现收缩趋势;样品的PL光谱存在明显的紫外发光峰、蓝光发光峰和绿光发光峰,而且峰位发生蓝移;同时一定量的Mn掺杂ZnS纳米晶在室温条件下具有铁磁性。     

Synthesis and Magnetic Properties of L0.5Sr0.5Mn0.5M0.5O3 (L = Y, Pr; M = Cu, Ru)

A new Mn-containing material with nominal composition L_0.5Sr_0.5Mn_0.5M_0.5O₃ (L = Y or Pr; M = Cu or Ru), as well as Y_0.5Sr_0.5MnO₃ for comparison, were synthesized. The results of the XRD and EDX analyses show that the obtained samples are single-phased and isostructural, with L_1–xA_xMnO₃. The L_0.5Sr_0.5Mn_0.5Cu_0.5O₃ material displays a PM behavior down to 8 K where paramagnetic–antiferromagnetic transition begins. The Pr_0.5Sr_0.5Mn_0.5Cu_0.5O₃ sample has a broad transition at 210 K and a magnetoresistance of 34% at 128 K. The Pr_0.5Sr_0.5Mn_0.5Ru_0.5O₃ material has a paramagnetic–ferromagnetic transition beginning at 330 K and a ferromagnetic–antiferromagnetic one at about 160 K. The obtained value of T _c is the highest for the Pr-containing manganites. The roles of Pr/Sr ratio, anisotropy, and intergranular effects in the samples are discussed.     

Review: Ferromagnetism in Undoped ZrO2 Thin Films

未掺杂氧化锆薄膜的铁磁性研究

宁帅,张政军（清华大学材料学院）

创新点说明：1,通过不同的物理气相沉积方法,实现了对未掺杂氧化锆薄膜的物相调控;2,发现了未掺杂氧化锆薄膜室温铁磁性对物相结构的依赖性;3,通过缺陷分析表征,发现四方相氧化锆的室温铁磁性主要由氧空位缺陷调控。

目的：未掺杂氧化锆薄膜的制备、物相和缺陷调控以及室温铁磁性研究。

方法：脉冲电子束沉积、直流反应磁控溅射、电子束蒸镀。

结果：1,通过不同的物理气相沉积方法,实现了未掺杂氧化锆薄膜的物相调控;2,发现了未掺杂氧化锆薄膜室温铁磁性的物相依赖性;3,通过缺陷分析表征,发现四方相氧化锆的室温铁磁性主要由氧空位缺陷调控。

结论： 1,制备了不同物相结构的未掺杂的氧化锆薄膜;2,发现了四方相氧化锆薄膜可以在室温下呈现铁磁性;3,四方相氧化锆薄膜中的室温铁磁性主要由氧空位缺陷引起。

关键词：氧化锆薄膜,物相调控,室温铁磁性,氧空位缺陷