共查询到19条相似文献,搜索用时 62 毫秒
1.
利用磁控溅射和快速热处理的方法制备了Mn,B共掺的多晶硅薄膜(Si0.9654Mn0.0346:B).磁性和结构研究发现薄膜有两个铁磁相.低温铁磁相来源于杂相Mn4Si7,高温铁磁相(居里温度TC~250K)是由Mn原子掺杂进入Si晶格导致.晶化后的薄膜利用射频等离子体增强化学气相沉积系统(PECVD)进行短暂(4min)的氢化处理后发现,薄膜的微结构没有发生变化而饱和磁化强度却随着载流子浓度的增大而增大.样品的饱和磁化强度和载流子浓度密切相关为验证在硅基磁半导体中磁性是以空穴为媒介的这一理论提供了有力的证据. 相似文献
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利用磁控溅射仪制备了高Co含量的Ti1-xCoxO2磁性半导体样品,并对样品分别在200℃,300℃和400℃进行退火研究.使用透射电子显微镜(TEM)对退火前后样品的结构进行表征,并用X射线光电子能谱(XPS)对退火前后样品中Co元素的化学状态进行鉴定.结果表明高Co含量的Ti1-xCoxO2磁性半导体处于一种亚稳状态,300℃以上的温度便使其结构与成分发生巨大变化.利用超导量子干涉磁强计(SQUID)测量退火前后样品的磁特性,结果表明样品的磁性有了明显的变化,这源于磁性产生的不同机理.
关键词:
磁性半导体
退火
磁性 相似文献
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通过往母合金Ni51.5Mn25Ga23.5掺入7种IVA, VA和VIA 过渡族元素得到系列掺杂合金Ni51.5Mn23M2Ga23 .5.M为掺杂元素.实验结果表明,掺杂效应一般引起马氏体相变温度的下降,其中,W 的掺杂是7种元素中唯一使相变温度升高的特例,且出现了中间马氏体相变.同时,在价电子 浓度不变的情况下,相变更敏感于原子的尺度效应.实验发现,Ti,Zr,Hf,V四种非磁性元 素的掺杂使Mn原子磁矩减小,而Nb,Ta,W三种非磁性元素的掺杂却可以明显地增大Mn原子 的磁矩.在考察掺杂效应时,不能忽略马氏体相变引起的晶格变化对材料磁性的影响.
关键词:
NiMnGa
掺杂
马氏体相变
磁性 相似文献
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文章研究了Cu替代部分Ni对铁磁性形状记忆合金Ni50Mn36In14相变和磁性的影响规律. 研究表明,在Ni50-xCuxMn36In14中,随着Cu含量的增加,相变温度逐渐降低. Cu含量低于5%时,奥氏体的磁性强于马氏体的磁性, 母相和马氏体相的饱和磁化强度的差值ΔM随着Cu含量的增加而增大. 当Cu含量x=4.5时, ΔM迅速增加到80 emu/g, 并在该材料中观察到了磁场驱动的马氏体到奥氏体的转变,显示了该材料作为磁驱动磁电阻材料的潜在应用前景.当Cu含量高于5%时,奥氏体保持铁磁状态, 马氏体相由反铁磁状态变为铁磁状态,马氏体的磁性强于奥氏体的磁性, ΔM大大削弱,磁场驱动性质消失. 相似文献
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Ghulam Murtaza Rai Muhammad Azhar Iqbal Yongbing Xu Iain Gordon Will Wen Zhang 《化学物理学报》2011,24(3):353-357
研究Ho3+掺杂对氧化锌半导体材料的微结构和磁学性质影响. 利用热蒸发技术制备了一系列沉积在Si(100)衬底的Zn1-xHoxO(x=0.0、0.04、0.05)薄膜. X射线光谱、表面形貌以及磁性的实验结果表明,Ho3+掺杂对ZnO薄膜材料的性能影响很大. X射线衍射图显示峰位出现高角度转变并且趋向于(101)取向,在ZnO晶格显示Ho3+置换. 扫描电子显微镜和能谱仪对薄膜的表面形貌以及化学 相似文献
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采用建立在经验赝势理论基础上的推广k·p方法及电流密度算符技术,计算了生长在Ge0.3Si0.7(001)衬底上的量子阱Ge0.3Si0.7/Si/Ge0.3Si0.7的导带电子束缚能级.详细地研究了因能谷间相互作用而引起的能级分裂情况,同时也讨论了电子束缚能级在阱平面方向上的色散关系
关键词: 相似文献
11.
Effect of hydrogenation time on magnetic and electrical properties of polycrystalline Si0.956Mn0.044:B thin films 下载免费PDF全文
This paper reports that polycrystalline Si 0.956 Mn 0.044 :B films have been prepared by cosputtering deposition followed by rapid thermal annealing for crystallization. The polycrystalline thin films were treated by hydrogen plasma excited with approach of radio-frequency plasma enhanced chemical vapour deposition for different time of 10 minutes, 15 minutes and 40 minutes. After hydrogenation, the structural properties of the films do not show any change, while both the saturation magnetization and the hole concentration in the films increase at first, then decrease with the increase of hydrogenation time. The obvious correlation between the magnetic properties and the transport properties of the polycrystalline Si 0.956 Mn 0.044 :B films suggests that a mechanism of hole-mediated ferromagnetism is believed to exist in Si-based diluted magnetic semiconductors. 相似文献
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Enhancement of ferromagnetism in polycrystalline Si0.965Mn0.035:B films by boron plasma treatment 下载免费PDF全文
This paper reports that the polycrystalline Si0.965Mn0.035:B films have been prepared by cosputtering deposition followed by rapid thermal annealing for crystallization. The polycrystalline thin films consist of two ferromagnetic phases. The low temperature ferromagnetic phase with Curie temperature (Tc) of about 50 K is due to the Mn4Si7 phase in the films, while the high temperature one (Tc~250 K) is resulted from the incorporation of Mn into silicon. The films are treated by boron plasma excited with the approach of microwave plasma enhanced chemical vapor deposition for 40 minutes. After plasma treatment, it is observed that no extra magnetic phases or magnetic complexes exist in the films, while both the high temperature saturation magnetization and the hole concentration in the films increase. The obvious correlation between the magnetic properties and the electrical properties of the polycrystalline Si0.965Mn0.035:B films suggests that the hole carriers play an important role in Si:Mn diluted magnetic semiconductors. 相似文献
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采用直流磁控溅射方法在玻璃基底上制备了不同Fe掺杂浓度的TiO2薄膜, 并对其晶体结构和磁特性进行了研究.在所有掺杂样品中,均观察到了室温铁磁性, 磁性源于Fe离子与其近邻空间分布的空穴相互作用. 在掺杂量为7%的锐钛矿相薄膜中观察到了最大的磁化强度. 随着Fe掺杂浓度的进一步增加, TiO2的晶体结构逐渐由锐钛矿相向金红石相转变,并且磁性减弱. 不同结构的TiO2中Ti–O键长不同,导致替代的磁性Fe离子与空穴的作用强度发生改变, 进而使其磁性发生变化.
关键词:
稀磁半导体
结构相变
铁磁性 相似文献
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Luyan Li Hui Liu Xiaoguang Luo Xiao Zhang Weihua Wang Yahui Cheng Qinggong Song 《Solid State Communications》2008,146(9-10):420-424
Room-temperature ferromagnetism is found in polycrystalline CrxZn1−xO (0≤x≤0.091) films prepared by magnetron sputtering. The saturated magnetization is 0.58 μB/Cr with x=0.012, and decreases with increased Cr dopant. The Curie temperatures of the samples are above 400 K. First principles calculations based on density functional theory predict that the electrons of Cr-doped ZnO films at Fermi level are 100% spin polarized when two Zn sites are substituted by Cr atoms in the nearest neighbour configuration. The spin polarized carriers and the p–d hybridization between Cr and its four neighbouring O atoms are responsible for observed ferromagnetism. 相似文献
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X. Marti A. Cattoni V. Laukhin C. Ferrater M. Varela J. Fontcuberta 《Journal of magnetism and magnetic materials》2009,321(11):1719-1722
Epitaxial orthorhombic YMnO3 thin films, (0 0 1) oriented, have been grown by pulsed laser deposition on (0 0 1)SrTiO3 substrates. Their crystal structure and magnetic response have been studied in detail. Although bulk o-YMnO3 is antiferromagnetic, our magnetic measurements reveal intriguing thermal hysteresis between the zero-field-cooled and field-cooled curves below the onset of the antiferromagnetic ordering temperature, thus signaling a more complex magnetic structure with net ferromagnetic moments. We discuss on the possible origin of this net magnetization and we have found a correlation of the magnetic response with the strain state of the films. We propose that substrate-induced strain modifies the subtle competition of magnetic interactions and leads to a non-collinear magnetic state that can thus be tuned by strain engineering. 相似文献
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对定向凝固方法制备的Ni47Mn32Ga21多晶合金,通过扫描电镜、金相、电子能谱等手段研究其组份和组织形貌,通过对合金磁化强度与温度关系、等温磁化曲线及磁感生应变曲线等的测量分析,研究了合金结构相变和磁相变过程中的磁熵变及不同压力下的磁感生应变. 研究结果表明:合金组份与设计组份基本一致,室温下合金大部分为马氏体相. 升温过程中合金的磁熵变在居里温度(365 K)附近有最大值,并有较大的磁熵变峰值半高宽,747 kA/m的磁场下该磁熵变最大值为-1.45 J/kg ·K,磁熵变峰值的半高宽为21 K. 合金在室温(298 K)下有较好的双向可恢复磁感生应变,480 kA/m磁场下,无压力时合金的磁感生应变值达到-670×10-6,并趋饱和;而在与磁场方向平行的27.3 MPa外压力作用下合金的磁感生应变值增大到-1300×10-6,且未饱和.
关键词:
Ni-Mn-Ga
铁磁形状记忆合金
磁熵变
磁感生应变 相似文献
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This study investigates the effect of annealing temperature on the Si0.8Ge0.2 epitaxial layers. The Si0.8Ge0.2 epitaxial layers were deposited by using ultrahigh vacuum chemical vapor deposition (UHVCVD) with different annealing temperatures (400-1000 °C). Various measurement technologies, including high-resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM) and interfacial adhesion tester, were used to characterize the materials properties of the SiGe epilayers. The experimental results showed that the SiGe epilayers gradually reduced lattice-mismatch to the underlying substrate as annealing temperature increased (from 400 to 800 °C), which resulted from a high temperature enhancing interdiffusion between the epilayers and the underlying substrate. In addition, the average grain size of the SiGe films increased from 53.3 to 58 nm with increasing annealing temperature. The surface roughness in thin film annealed at 800 °C was 0.46 nm. Moreover, the interfacial adhesion strength increased from 476 ± 9 to 578 ± 12 kg/cm2 with increasing the annealing temperature. 相似文献
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C. Sudakar P. Kharel R. Suryanarayanan J.S. Thakur V.M. Naik R. Naik G. Lawes 《Journal of magnetism and magnetic materials》2008
Thin films of pure TiO2 have been prepared using both spin-coating and sputter-deposition techniques on sapphire and quartz substrates. The structural characteristics of the films have been investigated in detail using Raman spectroscopy and high-resolution transmission electron microscopy (HRTEM). When annealed in vacuum, all films demonstrate room temperature ferromagnetism, while the air-annealed samples show much smaller, often negligible, magnetic moments. The magnetization of the vacuum-annealed sputtered samples depends on film thickness, with the volume magnetization decreasing monotonically with increasing thickness. Furthermore, the magnetization per unit area also decreases slightly with increasing film thickness. These results suggest that ferromagnetism in the vacuum-annealed TiO2 films is mediated by surface defects or interfacial effects, but does not arise from stoichiometric crystalline TiO2. 相似文献
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S. Karamat J.J. Lin P. Lee S.V. Springham R.S. Rawat 《Applied Surface Science》2008,254(22):7285-7289
The structural, magnetic and optical properties of (ZnO)1−x(MnO2)x (with x = 0.03 and 0.05) thin films deposited by pulsed laser deposition (PLD) were studied. The pellets used as target, sintered at different temperatures ranging from 500 °C to 900 °C, were prepared by conventional solid state method using ZnO and MnO2 powders. The observation of non-monotonic shift in peak position of most preferred (1 0 1) ZnO diffraction plane in XRD spectra of pellets confirmed the substitution of Mn ions in ZnO lattice of the sintered targets. The as-deposited thin film samples are found to be polycrystalline with the preferred orientation mostly along (1 1 0) diffraction plane. The UV-vis spectroscopy of the thin films revealed that the energy band gap exhibit blue shift with increasing Mn content which could be attributed to Burstein-Moss shift caused by Mn doping of the ZnO. The deposited thin films exhibit room temperature ferromagnetism having effective magnetic moment per Mn atom in the range of 0.9-1.4μB for both compositions. 相似文献