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1.
采用KKR-CPA-LDA方法研究了CuMnAl,CoMnAl和CuCoMnAl四元合金中磁性原子磁矩和Co-Mn间的交换作用.通过与实验结果对比,揭示了Mn的磁矩和Co的磁矩以及它们的相互作用随成分变化的规律.研究发现,在Cu50Mn25+xAl25-x合金中超过化学配比并占据Al位的Mn原子是反铁磁的,而且由于近邻环境的不同,其磁矩大于原有Mn原子的磁矩.在Co50Mn25+<
关键词:
KKR-CPA-LDA计算
Co-Mn间交换作用 相似文献
2.
利用X射线近边吸收谱对Fe2P,Ni2P及其掺杂物(Fe1-xNix)2P(x=01,025,05)中Fe,Ni,P的K边进行了研究.结合多重散射理论近边计算,讨论了金属原子不同位置格点3f,3g对近边谱特征的贡献,得出当Ni原子取代Fe原子时将优先占据Fe(3f)格点位置;根据第一性原理对能态的计算发现,不考虑磁性时不同格点P的pDOS未占据态电子结构与P-K近边吸收谱实验相符合;与考虑铁磁性Fe2P 的DOS相比较后结果显示Fe2P的磁性主要来源于Fe(3g)格点,铁磁性Ni2P计算的Ni不同格点原子磁矩均接近于0,与它一般显顺磁性结论相一致.
关键词:
X射线近边吸收谱
电子结构
多重散射理论
态密度 相似文献
3.
利用固相反应烧结技术制备La0.1Bi0.9-xEuxFeO3系列化合物. 利用X射线粉末衍射进行物相鉴定和结构分析,确定了材料的相关系:x≤0.05,材料为R3c结构相;0.08≤x≤0.12,材料为赝R3c结构相;x≥0.15是Pbnm相,其中0.15≤x≤0.20区域Pbnm相存在畸变. 磁测量结果表明,材料具有弱铁磁性,对于x≤0.20材料,磁矩在x=0.12成分存在极值. 利用阻抗分析仪测量了室温介电常数随成分的变化关系.讨论了材料的结构与弱铁磁性和室温介电常数间的关系.
关键词:
0.1Bi0.9-xEuxFeO3')" href="#">La0.1Bi0.9-xEuxFeO3
X射线衍射
磁性
介电常数 相似文献
4.
Tb$lt;sub$gt;0.3$lt;/sub$gt;Dy$lt;sub$gt;0.6$lt;/sub$gt;Pr$lt;sub$gt;0.1$lt;/sub$gt;(Fe$lt;sub$gt;1-$lt;i$gt;x$lt;/i$gt;$lt;/sub$gt;Al$lt;sub$gt;$lt;i$gt;x$lt;/i$gt;$lt;/sub$gt;)$lt;sub$gt;1.95$lt;/sub$gt;合金的磁性、磁致伸缩和穆斯堡尔谱研究
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系统研究了室温下Tb0.3Dy0.6Pr0.1(Fe1-xAlx)1.95 (x=0.05,0.1,0.15,0.2,0.25,0.3)合金中元素Al替代Fe对结构、磁性、磁致伸缩性能和自旋重取向的影响.测量结果发现,x<0.2时Tb0.3Dy0.6Pr0.1(Fe1-xAlx)1.95合金基本上是纯的单相,x=0.2时出现其他杂相,杂相随Al替代量的增加不断增多.随Al替代量x的增加,点阵常数a接近于线性增大,Curie温度TC逐渐下降,而矫顽力Hc急剧下降.振动样品磁强计(VSM)测量发现,磁化强度M随Al替代量x的变化较为复杂.VSM计和磁致伸缩效应测量共同表明,少量Al的替代有利于降低磁晶各向异性,而且随着Al替代量x的增多磁致伸缩系数快速减小,x>0.15时巨磁致伸缩效应消失.穆斯堡尔效应研究发现,随Al含量的增加Tb0.3Dy0.6Pr0.1(Fe1-xAlx)1.95合金中易磁化轴可能在{110}面逐渐偏离了立方晶体的主对称轴,发生自旋重取向,从而引起合金宏观磁性、磁致伸缩性能的变化.
关键词:
磁致伸缩
立方Laves相
自旋重取向
穆斯堡尔谱 相似文献
5.
6.
基于密度泛函理论中的广义梯度近似系统研究Mn(SiO2)3(M=Fe,Co,Ni;n=1-3)团簇的几何结构、光电性质和磁学性质.结果表明:Fe,Co原子相对于Ni原子更易于在(SiO2)3团簇上聚集;通过分析团簇的分裂途径及其产物,发现稳定性较好的氧化硅是一种很好的用于负载过渡金属"岛膜"的载体材料;Mn(SiO2)3团簇的能隙恰好位于近红外光谱范围内.通过磁性分析发现,该复合团簇的磁矩主要局域在过渡金属原子周围,而且,Fe2(SiO2)3和Co3(SiO2)3具有相对较大的磁矩,这主要源于过渡金属原子的d轨道间相互耦合.能隙和磁性两方面性质进一步肯定了二氧化硅磁性复合材料在医学界被用作光动力靶向治疗的可观前景. 相似文献
7.
用全势线性缀加平面波方法,考虑局域自旋密度近似研究虚晶掺杂MgCNi3的超导电性和磁性.计算了自旋极化能带结构、体弹性模量和它对压力的导数、原子磁矩m及其变化率.计算结果表明,对于电子掺杂的Mg1-xAlxCNi3(0≤x≤0.5),超导电性和磁涨落随掺杂量的增加逐渐减小.空穴掺杂的Mg1-xNaxCNi3,在x=0.12处出现铁磁相变,超导电性消失.在MgCNi3少量空穴掺杂区域(0≤x<0.12),表现为超导与磁涨落共存的不稳定状态.
关键词:
超导电性
能带结构
态密度
磁性 相似文献
8.
利用第一原理研究了过渡金属元素 Cr 或 Ni 在 Fe3Al合金中的优先占位行为及其合金化效应. 计算结果表明: Cr 或 Ni 的取代有助于Fe3Al 合金体系更稳定, Cr 优先占据 FeI 位, Ni 优先占据 FeII位. Fe2NiAl-II 具有最小的剪切模量G, 杨氏模量E和G/B值, 因此Fe2NiAl-II合金的韧性、延展性最佳. 态密度和电荷密度图表明, 过渡金属元素的取代提高了它们与近邻基体原子之间的相互作用, 削弱了Al和Fe的相互作用. 相似文献
9.
10.
通过对La2-xNdxCuO4+δ(0.1≤x≤1.2)体系中滞弹性弛豫与相变内耗性能的研究发现,当0.1≤x≤1.0时,在250K左右存在一个与间隙氧有关的弛豫内耗峰,并且当0.1≤x≤0.4时,弛豫内耗峰峰高随着x值的增大而升高,此时体系为正交结构;当0.5≤x≤1.0时,体系在宏观上呈现四方结构,此时内耗峰峰高随着x<
关键词:
2-xNd<i>xCuO4+δ')" href="#">La2-xNd<i>xCuO4+δ
间隙氧
弛豫内耗峰
相变内耗峰 相似文献
11.
采用快速液相烧结法制备BiFeO3和Bi0.95Dy0.05Fe1-xCoxO3 (x=0, 0.05, 0.1, 0.15)陶瓷样品. 实验结果表明: 所有样品的主衍射峰与纯相BiFeO3相符合且具有良好的晶体结构, 随着Co3+掺杂量的增大, Bi0.95Dy0.05Fe1-xCoxO3样品的主 衍射峰由双峰(104)与(110)逐渐重叠为单峰(110), 当掺杂量x>0.05时, 样品呈现正方晶系结构; SEM形貌分析可知: Dy3+, Co3+共掺杂使BiFeO3晶粒尺度由原来的3—5 μ减小到约1 μ. 室温下, BiFeO3样品表现出较弱的铁磁性, 随着Dy3+和Co3+掺杂, BiFeO3样品的铁磁性显著提高. 在外加磁场为30 kOe的作用下, Bi0.95Dy0.05Fe1-xCoxO3 (x=0.05, 0.1, 0.15)的Mr分别为0.43, 0.489, 0.973 emu/g; MS分别为0.77, 1.65, 3.08 emu/g. BiFeO3和Bi0.95Dy0.05Fe1-xCoxO3样品磁矩M随着温度T的升高而逐渐减小, Dy掺杂使BiFeO3样品的TN由644 K升高到648 K, 而TC基本没有变化. Dy和Co共掺杂导致BiFeO3样品磁相变温度TC由870 K降低到780 K, 其TC变化主要取决于Fe-O-Fe反铁磁超交换作用的强弱和磁结构的相对稳定性.
关键词:
铁磁电材料
磁滞回线
磁相变温度 相似文献
12.
K. Yoshimura Y. Yoshimoto M. Mekata T. Sakakibara T. Goto 《Journal of magnetism and magnetic materials》1987,70(1-3):147-148
High field magnetization measurements have been performed to examine the existence of itinerant metamagnetism in exchange-enhanced systems related to YCo2 together with Fe1−x CoxSi. In the Y(Co−xFex)2 system, the meta magnetism inherent in YCo2 has been observed in 0.04 x0.07. The transition is not as sharp as in the Y(Co1−xAlx)2 system. Other exchange-enhanced paramagnets Y(Co−xCux)2 and Y1−xLaxCox2 and weakly itinerant ferromagnet Fe1−xCoxSi exhibit no metamagnetic transition up to 430 kOe. 相似文献
13.
M. Motokawa S. Kawarazaki H. Nojiri T. Inoue 《Journal of magnetism and magnetic materials》1987,70(1-3):245-246
Magnetization measurements are made in pulsed magnetic fields up to 200 kOe at 4.2 K and up to 100 kOe at various temperatures on the alloys Fe1−xCoxSi. In the paramagnetic region of x<0.05 or x0.7, we expected a metamagnet transition at high field but no remarkable change of magnetization is observed. 相似文献
14.
Magnetic transitions in La(Fe1−xCox)11.4Si1.6 compounds with x=0–0.08, have been studied by DC magnetic measurements and Mössbauer spectroscopy. The temperature dependence of the Landau coefficients has been derived by fitting the magnetization, M(μ0H), using the Landau expansion of the magnetic free energy. For x0.02 there is a strongly first-order magnetic phase transition between ferromagnetic and paramagnetic (F–P) states in zero external field and a metamagnetic transition from paramagnetic to ferromagnetic (P–F) above Tc. Increasing the cobalt content drives the F–P transition towards second order and eliminates the metamagnetic transition. 相似文献
15.
Phonon anomalies have been reported in iron-pnictide superconductors indicating a diverse interplay between different orders in the materials.Here,we report Raman scattering measurements on Sr(Fe1-xCox)2As2(x=0 and x=0.04)single crystals in the B;symmetry with respect to a 1 Fe unit cell.Upon cooling,we observe a larger split(13 cm;)of Eg Raman phonon modes pertaining to in-plane Fe and As displacements as the crystals undergo the tetragonal-toorthorhombic structural phase transition,although a considerable split(9 cm;)has been reported in BaFe1-xCox)2As2.Furthermore,the splitting of E;phonon modes is strongly reduced upon doping.We perform an order-parameter analysis revealing a similar doping dependence of E;phonon splitting as reported in other compounds of the 122 family,indicating these phonon anomalies widely exist in 122 iron-based superconductors and might share the same mechanisms. 相似文献
16.
本文采用高温有机溶剂法制备了(Fe1-xCox)3BO5纳米棒, 通过控制反应物中乙酰丙酮钴的含量合成了不同Co含量的(Fe1-xCox)3BO5. 利用高分辨透射电子显微镜(HRTEM)、超导量子干涉磁强计(SQUID)对其形貌和磁性能进行了表征. 高分辨透射电子显微镜结果表明制备出的纳米(Fe1-xCox)3BO5为多晶棒状, 且具有多折孪晶结构; 磁性测量的结果表明,(Fe1-xCox)3BO5纳米棒在室温下表现出铁磁性, 随着Co含量的增加, 纳米棒的铁磁性逐渐增加, 该纳米棒有望用来研究生物大分子的机械性能. 相似文献
17.
The magnetic properties and magnetocaloric effect(MCE) in EuTi_(1-x)Co_xO_3(x = 0, 0.025, 0.05, 0.075, 0.1) compounds have been investigated. When the Ti~(4+) ions were substituted by Co2+ions, the delicate balance was changed between antiferromagnetic(AFM) and ferromagnetic(FM) phases in the EuTiO_3 compound. In EuTi_(1-x)Co_xO_3 system, a giant reversible MCE and large refrigerant capacity(RC) were observed without hysteresis. The values of -?S_M~(max) were evaluated to be around 10 J·kg~(-1)·K~(-1) for EuTi_(0.95)Co_(0.05)O_3 under a magnetic field change of 10 kOe. The giant reversible MCE and large RC suggests that EuTi_(1-x)Co_xO_3 series could be considered as good candidate materials for low-temperature and low-field magnetic refrigerant. 相似文献
18.
Xiao-Hong Xu Xiu-Fang Qin Feng-Xian Jiang Xiao-Li Li Ya Chen G.A. Gehring 《Applied Surface Science》2008,254(16):4956-4960
A series of Zn1−xCoxO thin films with the atomic fraction, x, in the range of 0.03–0.10 were deposited on glass substrates at room temperature by magnetron co-sputtering technique and subsequently coupled with the post-annealing treatment for half hour at different temperatures (350 °C and 500 °C) under vacuum. A systematic study was done on the structural, optical and magnetic properties of Zn1−xCoxO thin films as a function of Co concentration and annealing temperature. X-ray diffraction and UV–vis spectroscopy results indicated that there are not any secondary phases and Co2+ substituted for Zn2+ of ZnO host. Magnetic hysteresis loops were observed at room temperature, indicating that both the as-deposited samples and the annealed ones exhibit the room temperature ferromagnetism. It was also found that the magnetic saturation moment per Co atom decreases with increasing Co concentration, while the post-annealing treatment can enhance the magnetic moment of the films effectively. 相似文献
19.
Effects of phosphorus doping on the physical properties of axion insulator candidate EuIn2As2
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Feihao Pan 《中国物理 B》2022,31(5):57502-057502
We report an investigation on the single crystal growth, magnetic and transport properties of EuIn2(As1-xPx)2 (0≤x≤ 1). The physical properties of axion insulator candidate EuIn2As2 can be effectively tuned by P-doping. With increasing x, the c-axis lattice parameter decreases linearly, the magnetic transition temperature gradually increases and ferromagnetic interactions are enhanced. This is similar to the previously reported high pressure effect on EuIn2As2. For x=0.40, a spin glass state at Tg=10 K emerges together with the observations of a butter-fly shaped magnetic hysteresis and slow magnetic behavior. Besides, magnetic transition has great influence on the charge carriers in this system and negative colossal magnetoresistance is observed for all P-doped samples. Our findings suggest that EuIn2(As1-xPx)2 is a promising material playground for exploring novel topological states. 相似文献
20.
Alex Trukhanov Larisa Panina Sergei Trukhanov Vitalii Turchenko Mohamed Salem 《中国物理 B》2016,25(1):16102-016102
The investigations of the crystal and magnetic structures of the Ba Fe12-xAlx O19(x = 0.1–1.2) solid solutions have been performed with powder neutron diffractometry. Magnetic properties of the Ba Fe12-xAlx O19(x = 0.1–1.2) solid solutions have been measured by vibration sample magnetometry at different temperatures under different magnetic fields.The atomic coordinates and lattice parameters have been Rietveld refined. The invar effect is observed in low temperature range(from 4.2 K to 150 K). It is explained by the thermal oscillation anharmonicity of atoms. The increase of microstress with decreasing temperature is found from Rietveld refinement. The Curie temperature and the change of total magnetic moment per formula unit are found for all compositions of the Ba Fe12-xAlx O19(x = 0.1–1.2) solid solutions. The magnetic structure model is proposed. The most likely reasons and the mechanism of magnetic structure formation are discussed. 相似文献