共查询到19条相似文献,搜索用时 93 毫秒
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利用固相反应法制备了名义成分为Ca(Mn2Cu1)Mn4O12的类钙钛矿锰氧化物.x射线衍射表明,为了获得较为致密的样品和减小杂相含量,可以采用高温烧结再在1073K长时间空气中退火的制备方法.样品在低温下同时存在铁磁相和反铁磁相,由于反铁磁相的存在导致样品在4.5K时的磁化强度显著降低,并在8T的高磁场下仍未达到饱和.样品呈半导体导电性质,在85K和6T磁场下磁电阻比的最大值可达-46%.
关键词:
[AC3](B4)O12类钙钛矿锰氧化物
庞磁电阻效应
铁磁性
反铁磁性 相似文献
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利用固相反应法制备了Nd2-2x Ca1+2x Mn2O7(x=0.0-0.9)多晶样品,通过FULLPROF程序对样品X射线衍射图谱进行了精修,样品的空间群为14/mmm.测量了样品x=0.4,0.5的磁性(5K相似文献
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利用湿化学反应法制备了CaCuxMn3-xMn4O12(x=0.2,0.4,0.6,0.8,1.0,1.2,1.4)系列材料的前驱体,然后加入10wt%的KCL后,在850℃的纯氧中烧结制成样品。X射线衍射表明,CaCuxMn3-xMn4O12样品呈单相立方结构,空间群Im 3-。研究表明:随掺杂浓度x的增加,晶格常数减小,晶体结构发生畸变,从而直接影响材料的电输运性质。实验表明,样品在5T的外磁场下,随x的增大,样品的磁电阻MR呈现先增大后减小的趋势,在x=1.0时磁电阻达到最大,这可能是晶粒边界处粒子的自旋极化散射和双交换作用共同作用的结果。 相似文献
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系统研究了xAg-La0.67(Ca0.65Ba0.35)0.33MnO3和xPd-La0.67(Ca0.65Ba0.35)0.33MnO3(xAg-LCBMO和xPd-LCBMO)两种复合体系的电特性和磁电阻特性. 结果发现,Pd和Ag的掺杂都引起电阻率的大幅降低和峰值电阻率温度的升高,这主要源于晶粒边界/表面良导体金属晶粒的析出. 另外,Pd和Ag的掺杂都引起室温磁电阻的大幅增强. 尤其是27%摩尔比的Ag掺杂诱导了高达70%的室温磁电阻,几乎是未掺杂母体LCBMO的10倍,而27%摩尔比的Pd掺杂诱导产生了更高的磁电阻,约170%. 磁电阻的大幅增强,与良导体金属掺杂引起的样品电阻率的降低有关. 另一方面,晶粒表面/边界Mn离子与Pd离子接近诱导Pd离子的自旋极化对磁电阻的增强起了重要的促进作用. 相似文献
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本文用对靶溅射技术制备了La2/3Ca1/3MnO3/YBa2Cu4O8/La2/3Ca1/3MnO3薄膜.与YBCO单层薄膜相比,由于超导/铁磁系统中的磁性邻近效应,三层薄膜表现出较低的超导转变温度.薄膜的R~T测量曲线显示出超磁阻(CMR)效应和超导转变,预示着超导和铁磁特性共存于LCMO/YBCO/LCMO三文治结构. 相似文献
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采用固相烧结工艺,制备了不同La掺杂量(x=0.00,0.25,0.50,0.75,1.00,1.25和1.50)的(Bi, La)4Ti3O12-Sr(Bi, La)4Ti4O15 (SrBi8-xLaxTi7O27)共生结构铁电陶瓷样品.用x射线衍射对其进行微结构分析,并测量铁电、介电性能.结果发现,La掺杂未改变Bi4Ti3O12-SrBi4Ti4O15共生结构铁电材料的晶体结构.随掺杂量的增加,样品的矫顽场(Ec)略有增加,剩余极化(2Pr)先增大,后减小.在x=0.50时,2Pr达到极大值,为25.6 μC*cm-2,与Bi4Ti3O12-SrBi4Ti4O15相比,2Pr增加了近60%,而Ec仅增加约10%.随La掺杂量的增加,样品的居里温度TC逐渐降低,x=0.50时,TC=556 ℃.在x=1.50时,样品出现弛豫铁电体的典型特征. 相似文献
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The layered manganite Nd2−2x
Sr1+2x
Mn2O7, with x varying between 0 and 0.5, has been synthesized using solid-state reaction method. We have found that Nd2−2x
Sr1+2x
Mn2O7 do not form the single-phase layered compound with A3B2O7 structure. Instead, mixtures of various phases, such as, orthorhombic perovskite, i.e., Nd1−z
Sr
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MnO3, layered manganite and unreacted starting compounds, have been obtained. Except for x=0.4, which is found to be an antiferromagnetic insulator, all other x values yielded metal-insulator transition and ferromagnetic ordering. 相似文献
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采用溶胶凝胶工艺在p-Si衬底上制备了SrBi2Ta2O9/Bi4Ti3O12复合铁电薄膜. 研究了SrBi2Ta2O9/Bi4Ti3O12复合薄膜的微观结构与生长行为、铁电性能和疲劳特性. 研究表明: Si衬底Bi4Ti3O12薄膜易于沿c轴择优生长,并有利于SrBi2Ta2O9/Bi4Ti3O12复合薄膜的生长.合理的SrBi2Ta2O9/Bi4Ti3O12厚度配比能获得较好的铁电性能和优良的抗疲劳特性,SrBi2Ta2O9/Bi4Ti3O12厚度配比为1∶3的复合薄膜的剩余极化强度和矫顽电场分别为8.1 μC/cm2 和 130 kV/cm,其无疲劳极化开关次数达1011以上. 相似文献
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Shaobo Yang Jianping Zhong Jun Miao Jie Yuan Bo Xu Lixin Cao Xianggang Qiu Bairu Zhao Zhong Xie Lihua Zhao 《Physica B: Condensed Matter》2005,370(1-4):99-103
The electronic and magnetic phase transitions of Pr0.5−xLaxSr0.5MnO3 with x=0.10 and 0.15 were investigated. The M(T) and ρ(T) curves for these samples clearly show transitions from antiferromagnetic insulator to ferromagnetic semiconductor, ferromagnetic metal and finally to paramagnetic semiconductor as the temperature is increased from 5 to 300 K. Especially, two obvious protrudent peaks in the magnetoresistance curves MR(T) for these samples were clearly observed in the relative low magnetic field, 1 T. One peak appears at around the antiferromagnet-ferromagnet transition temperature TN (150 K) with MR≈−23%, another occurs at around the ferromagnet-paramagnet transition temperature TC(275 K ) with MR≈−8.2%. In addition, when the magnetic field was increased, the temperature corresponding to the MR peak at TN shifts to lower temperature while the temperature corresponding to the MR peak at TC is fixed. 相似文献
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Self-assembling conditions for 1O4Ca tetrahedral nanoclusters in ZnTe:(Ca, O) with Ca content up to 0.02 and with the ultradilute limit of oxygen are represented. The causes of self-assembling are a CaO and ZnTe bonding preferential over a CaTe and ZnO one and decrease of the strain energy after nanocluster formation. Self-assembling conditions were studied in the temperature range from 200 °C to 1305 °C. The occurrence of nanoclusters depends only on the Ca content and temperature. The temperature of self-assembling completion when all oxygen atoms are in 1O4Ca nanoclusters is determined by the Ca and oxygen contents. 相似文献
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Magnetic properties and magnetoresistance of HfFe2Ge2-type Dy1-xGdxMn6Ge6 (x=0.1-0.6) compounds 下载免费PDF全文
The magnetic properties and magnetoresistance effects of Dy_{1-x}Gd_xMn_6Ge_6 (x=0.1-0.6) compounds have been studied by magnetic properties and resistivity measurements in applied magnetic fields up to 5T. The compounds with x=0.1, 0.2, 0.4 and 0.5 order antiferromagnetically at 425, 428, 430 and 432K, respectively, and there are second magnetic phase transitions below 100K. The compound with x=0.6 exhibits a transition from ferrimagnetic to antiferromagnetic, then to ferrimagnetic state again with decreasing temperature. Furthermore, it displays a field-induced metamagnetic transition, and its threshold field decreases with increasing temperature. The magnetoresistance curve of the compound with x=0.6 in applied magnetic fields up to 5T is presented and the magnetoresistance effects are related to the metamagnetic transitions. 相似文献