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本文通过传统的固相反应法制备了R型六角铁氧体BaFe4-xTi2+xO11 (x= 0, 0.25, 0.5, 0.75, 1), 并且对它的原子价态以及磁性行为进行了研究. X 射线光电子能谱(XPS)结果显示了随着掺杂含量的增加, 体系中Fe3+离子逐渐减少而Fe2+离子逐渐增加. 由于具有非对称结构的阻挫晶格中存在各种关联作用的竞争, 使得BaFe4-xTi2+xO11体系表现出了复杂的磁有序行为, 在T1~250 K和T2~83 K两处存在磁转变. 对这一系列掺杂样品, 在相变温度T1之上表现顺磁行为, 而在相变温度T2前后的磁化强度都表现出低场下随磁场的增加快速增加, 高场下则线性变化且在5×104 Oe时还未达到饱和的行为, 表明这一系列掺杂样品是典型的倾斜反铁磁态(canted antiferromagnetic) 或者亚铁磁态. 相似文献
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We present the temperature-dependent susceptibility and specific heat measurement of spinel ZnV_2O_4.The structural transition with orbital ordering and the antiferromagnetic transition with spin ordering were observed at 50 K and 37 K,respectively.By analysis of the hysteresis behavior between the specific heat curves obtained in warming and cooling processes,the structural transition was confirmed to be the first-order transition,while the antiferromagnetic transition was found to be of the second-order type.At the structural transition,the latent heat and entropy change were calculated from the excess specific heat,and the derivative of pressure with respect to temperature was obtained using the Clausius-Clapayron equation.At the magnetic transition,the width of the critical fluctuation region was obtained to be about 0.5 K by comparing with Gaussian fluctuations.In the critical region,the critical behavior was analyzed by using renormalization-group theory.The critical amplitude ratio A~+/A~- = 1.46,which deviates from the 3D Heisenburg model;while the critical exponent α is-0.011,which is close to the 3D XY model.We proposed that these abnormal critical behaviors can be attributed to strong spin-orbital coupling accompanied with the antiferromagnetic transition.Moreover,in the low temperature range(2-5 K),the Fermi energy,the density of states near the Fermi surface,and the low limit of Debye temperature were estimated to be2.42 eV,2.48 eV~(-1),and 240 K,respectively. 相似文献
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La$lt;sub$gt;0.4$lt;/sub$gt;Ca$lt;sub$gt;0.6$lt;/sub$gt;MnO$lt;sub$gt;3$lt;/sub$gt;中Mn-位Fe和Cr掺杂对磁性质的影响 下载免费PDF全文
研究了Fe和Cr掺杂对La0.4Ca0.6MnO3 中电荷有序反铁磁基态的调控作用. 磁性质的测量结果表明, 两种离子掺杂均能有效抑制原型样品中的长程电荷有序相, 但是Fe离子掺杂样品均具有反铁磁的基态, 而Cr掺杂样品中则出现了显著的铁磁性. 结合电输运测量结果显示, Cr掺杂引起的铁磁态同时具有金属性, 表明其中是电子双交换作用占主导. 对比两种掺杂离子的电子结构发现, Cr离子空的eg电子轨道促进了电子双交换作用, 而Fe掺杂则只是引入了不同的自旋交换作用, 导致自旋无序.
关键词:
磁性氧化物
反铁磁 相似文献
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利用固相反应法制备了Sr14Cu24O41及其系列B位掺杂Sr14(Cu0.97M0.03)24O41(M=Zn,Ni,Co)的样品.X射线衍射分析显示,所有样品均为纯相,晶格常数a与c没有明显的变化;Zn掺杂样品晶格常数b没有明显变化,而Ni,Co掺杂样品晶格常数b分别稍有增加.选区电子衍射研究揭示:磁性元素Ni,Co及非磁性元素Zn掺杂,可能主要替代了Sr14Cu24O41结构中自旋链上的Cu原子,从而影响了自旋链上的dimer排列,破坏电荷有序超结构.电输运测量显示:Zn2+,Ni2+,Co3+离子掺杂样品的电阻率降低,但仍体现半导体行为,所有的掺杂样品都存在一个渡越温度Tρ,当TTρ时,其导电机理是以单空穴热激发导电占主要地位,在TTρ时,配对的局域化空穴的一维变程跳跃导电占主要优势;在相同的掺杂量下,非磁性元素Zn掺杂对电阻率值的影响大于磁性元素Ni,Co掺杂的影响,而磁性元素Ni,Co掺杂对渡越温度Tρ的影响大于非磁性元素Zn掺杂的影响. 相似文献
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Ho and Ti co-doped BiFeO_3 multiferroic ceramics with enhanced magnetization and ultrahigh electrical resistivity 下载免费PDF全文
Bi0.9Ho0.1Fe0.95O3 and Bi0.9Ho0.1Fe0.9Ti0.05O3 ceramics were prepared and compared to reveal the effects of Ho and Ti codoping in BiFeO3. X-ray diffraction indicated that both ceramics had a high rhombohedral perovskite phase content, and microstructural analyses showed that the grains of the Bi0.9Ho0.1Fe0.9Ti0.05O3 ceramics were much smaller than those of Bi0.9Ho0.1Fe0.95O3. An electrical resistivity of more than 1 × 1014?·cm at room temperature, and a magnetic hysteresis loop with a remnant magnetization 2Mr of ~ 0.485 emu/g were obtained for Bi0.9Ho0.1Fe0.9Ti0.05O3; both were much higher than those of Bi0.9Ho0.1Fe0.95O3. Changes in the defect subsystem of BiFeO3 induced by Fe-deficiency and(Ho,Ti) codoping are proposed as being responsible for the improvement in the properties. 相似文献
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Ho and Ti co-doped BiFe03 multiferroic ceramics with enhanced magnetization and ultrahigh electrical resistivity 下载免费PDF全文
Bio.9HOo.lFeo.9503 and Bio.9HOo.lFeo.9Tio.0503 ceramics were prepared and compared to reveal the effects of Ho and Ti codoping in BiFeO3. X-ray diffraction indicated that both ceramics had a high rhombohedral perovskite phase content, and microstructural analyses showed that the grains of the Bio.9HOo.lFeo.9Tio.0503 ceramics were much smaller than those of Bio.9HOo.lFeo.9503. An electrical resistivity of more than 1 × 1014.cm at room temperature, and a magnetic hysteresis loop with a remnant magnetization 2Mr of 0.485 emu/g were obtained for Bi0.9HO0.1Fe0.9Ti0.0503; both were much higher than those of Bio.9Hoo.1Feo.9503. Changes in the defect subsystem of BiFeO3 induced by Fe-deficiency and (Ho,Ti) codoping are proposed as being responsible for the improvement in the properties. 相似文献