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| 1 | La_(0.4)Ca_(0.6)Mn_(1-x)Ga_xO_3体系的电荷有序相显示文摘用固相反应法制备La0.4Ca0.6Mn1-xGaxO3(x=0,0.08,0.10,0.12,0.15)系列多晶样品。通过X射线衍射(XRD)图谱、电阻率-温度(ρ-T)曲线、磁化强度-温度(M-T)曲线和电子自旋共振(ESR)图谱,研究Ga3+替代Mn3+对La0.4Ca0.6Mn1-xGaxO3体系电荷有序相的影响。结果表明,当Ga掺杂量高达15%时电荷有序相仍然没有被破坏。这是因为Ga3+是非磁性离子,而La0.4Ca0.6MnO3是CE型反铁磁电荷有序相结构,Ga3+替代Mn3+只是仅仅起到把体系中的长程自旋序破坏为短程自旋序的作用,同时随Ga替代量增大,Mn3+与Mn4+的比远离双交换的最佳摩尔配比(Mn3+∶Mn4+=2∶1),不利于双交换,因而非磁性的Ga3+替代Mn3+难以破坏La0.4Ca0.6MnO3的电荷有序相。 | 刘鹏 王桂英 唐永刚 毛强 刘宁 彭振生 | 2014 | 稀有金属2014，38，4： | 6 |
| 2 | Co替代Mn的La_(0.4)Ca_(0.6)Mn_(1-x)Co_xO_3的磁电性质及电荷有序相显示文摘用固相反应法制备La0.4Ca0.6Mn1-xCoxO3(x=0.02,0.04,0.06,0.08,0.10,0.12)系列样品,用X射线衍射(XRD)探测样品的结构,通过电阻率-温度(ρ-T)曲线、磁化强度-温度(M-T)曲线、电子自旋共振(ESR)谱,研究Co替代Mn对La0.4Ca0.6Mn O3磁电性质及电荷有序相的影响。结果表明:XRD图谱显示所有样品均形成良好的单相,没有任何杂相出现,说明Co已经进入Mn位并结晶良好;随Co替代量的增大,电阻率逐渐减小;随Co替代量的增大,反铁磁性减弱,铁磁性增强;x=0.02的样品,电荷有序相已基本融化,还有一些电荷有序相的残留,x=0.06的样品,电荷有序相完全融化。物理机制是,Co3+的电子结构是3d6,符合Oh对称,它不是Jahn-Teller(JT)离子,因为Co3+不是JT离子,所以Co3+替代Mn3+抑制了JT畸变。JT畸变减弱引起的影响:一方面使Mn3+—O2-—Mn4+键长缩短,键角增大,有利于双交换;另一方面,Mn3+的两个eg轨道劈裂产生带隙,Co3+替代Mn3+使带隙减小,提高了材料的导电性,使体系反铁磁性减弱铁磁性增强,从而破坏电荷有序相。 | 王桂英 刘鹏 李莉 叶吾梅 刘宁 彭振生 | 2015 | 稀有金属2015，39，5： | 5 |
| 3 | Temperature stability of magnetoresistance (MR) and MR enhancement in La_(1-x)(Sr_(1-y)Ag_y)_x MnO_3 system显示文摘Polycrystalline samples of La12x(Sr12yAgy)x MnO3 (y = 0.0, 0.2, 0.4, 0.6, 1.0) were prepared by the solid-state reaction method. The temperature stability of magnetoresistance and magnetoresistance enhancement in La1-x(Sr1-yAgy)x MnO 3 system with both univalent and bivalent elements doped at A site and with unchanged value of Mn3+ /Mn4+ ratio were explored through the measurements of X-ray diffraction patterns, magnetiza-tion-temperature (M-T) curves, resistivity-temperature (q-T) curves and magnetoresistance-temperature (MR-T) curves. The results are as follows: there are two peaks in the q-T curves of the samples with Ag doping, one is caused by resistance change during the paramagnetism-ferromagnetism transition, and the other is from boundary-dependent scattering of conduction electrons on the boundaries of grains. The peak value of MR increases with increasing Ag doping content, and it increases from 8.2 % for y = 0.2 to 29.6 % for y = 1.0 under the magnetic field of B = 0.8 T; MR remains a constant of 12 % in the temperature range of 218-168 K for the sample with y = 1.0, and the temperature stability of MR is in favor of the practical application of MR. | Yong-Gang Tang Gui-Ying Wang Guo-Qing Yan Qi-Xiang Song Ming-Yu Zhang Zhen-Sheng Peng | 2013 | Rare Metals2013，32，1： | 1 |
| 4 | RARE METALS显示文摘 | | 2013 | Rare Metals2013，32，1： | 0 |
| 5 | Co替代Mn对Pr_(0.6)Ca_(0.4)MnO_3磁性质及电荷有序的影响显示文摘用固相反应法制备Pr_(0.6)Ca_(0.4)Mn_(1-x)CoxO_3(x=0,0.02,0.04,0.06)系列多晶样品。通过X射线衍射(XRD)图谱检测样品的结构,通过零场冷(ZFC)和加场冷(FC)的磁化强度-温度(M-T)曲线,电子自旋共振(ESR)图谱,研究Co替代Mn对Pr_(0.6)Ca_(0.4)Mn O_3磁性质及电荷有序相的影响。结果表明:母体样品的宏观磁性质随温度的变化而发生多重变化,在238 K出现电荷有序相,TCO=238 K,200~173 K温区的ZFC曲线出现一个平台,173 K为Neel温度,即T_N=173 K,在40 K附近ZFC曲线出现一个尖峰,样品出现自旋玻璃态,自旋玻璃态转变温度T_f=40 K。Co替代Mn对Pr_(0.6)Ca_(0.4)Mn O_3的磁性质及电荷有序相影响明显,所有掺Co样品都没有表现出电荷有序特征,随温度降低从顺磁向铁磁/反铁磁混合相转变。Co替代Mn对电荷有序的破坏非常容易,当Co替代量x=0.02时电荷有序相被完全融化。Co替代Mn对电荷有序相的破坏之所以容易,是因为用非Jahn-Teller(JT)离子Co^(3+)替代JT离子Mn^(3+),削弱了Jahn-Teller畸变,间接证明Jahn-Teller电-声子相互作用是产生电荷有序的主要原因。 | 胡学青 王桂英 刘鹏 罗鹏 李莉 彭振生 | 2016 | 稀有金属2016，40，6： | 0 |
| 6 | Processing stages of Gd_2Sr(Al_(1-x)Fe_x)_2O_7 series显示文摘The continuous series of perovskite-related oxides with the general formula Gd2 Sr(Al1-x Fex)2 O7 0 \ x \ 1 were prepared by conventional ceramic technology in air. The processing stages of Gd2 Sr(Al1-x Fex)2 O7 0 \ x \ 1 phases were investigated by means of X-ray powder diffraction(XRD) and scanning electron microscopy(SEM) with the element phase analysis. The three main stages of Gd2 Sr(Al1-x Fex)2 O7 formation are pointed out. The analysis of the mutual influence of intermediate compounds on the synthesis of the target solid solutions of complex composition, in particular for Gd2 Sr(Al1-x Fex)2 O7 was carried out. It is determined that the closeness of the reactive mixture composition to the composition of individual compounds Gd2 SrAl2 O7 or Gd2 SrFe2 O7 is of importance for the realization of a particular way of Gd2 Sr(Al1-x Fex)2 O7 solid solutions formation. It is shown that at x & 0.2 the reversing in scheme of Gd2 Sr(Al1-x Fex)2 O7 series formation is observed. The formation of the Gd2 Sr(Al1-x Fex)2 O7 continuous series is indicated by the monotonic dependence of molar unit cell volume on the iron content x. | Ekaterina Tugova Victor Gusarov | 2014 | Rare Metals2014，33，1： | 0 |
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