La-Gd-Ca-Mn-O的磁性、电性和磁电阻效应

在La0 67Ca0 33 MnO3 中进行了掺Gd研究 ,结果发现 ,经 140 0℃烧结的样品 ,获得了最佳的磁电阻效应。随掺Gd量增加 ,材料的相变温度逐渐下降 ,对应的峰值电阻率大幅度增加 ,居里温度逐渐下降 ,磁电阻比明显提高。掺入 11%的Gd后 ,可以使磁电阻比提高一个数量级。这些变化可以用晶格效应来解释。     

Dy和Yb部分替代La0.67Ca0.33MnO3中的La的影响

用Dy和Yb部分替代La0.67Ca0.33MnO3中的La使材料的居里温度单调下降，掺Dy使材料的相变温度单调下降，峰值电阻率迅速增大，磁电阻比急剧增大，掺入13％（原子分数）的Dy可使材料的最大磁电阻比增大近40倍，而掺Yb对磁电阻的影响要小得多，用自旋团簇理论可以解释庞磁电阻的形成。     

CEMS AND COUPLING EFFECT OF INTERLAYERS IN MULTILAYERED FeSi/Si AMORPHOUS FILMS

Multilayered FeSi/Si amorphous films with fixed FeSi layer thickness and different Si layer thicknesses have been studied by conversion electron Mossbauer spectroscopy at room temperature. The results showed that with decreasing the Si layer thickness, the hyperfine field of samples increased and the thickness of interface dead layers arisen from the atomic interdiffusion effect decreased. These are due to the coupling effect between the magnetic layers. When the Si layers are thinner than 0.88 nm, the direction of the magnetization is out of the film plane.     

纳米Fe-In2O3颗粒膜中Fe的晶格结构和尺度效应

采用射频溅射法制备了纳米“铁磁金属-半导体基体”Fe-In2O3颗粒膜，研究了颗粒膜中纳米Fle颗粒的晶格结构和尺度效应．结果表明：Fe-In2O3颗粒膜中纳米Fe颗粒晶格发生畸变，原子间距随颗粒尺寸的减小而增大；纳米Fe颗粒的比饱和磁化强度MS和Curie温度TC随颗粒尺寸减小而降低．探讨分析了Fe-In2O3颗粒膜中纳米Fe颗粒的MS和TC随颗粒尺寸变化的原因．     

Spin Dependent Hopping in Ti Doped La0.67 Ca0.33 MnO3

A systematic investigation of the magnetic and transport properties of Ti doped La0.67Ca0.33MnO3 was reported. The Ti substitution for Mn ions results in a reduction in ferromagnetism and conductivity. The metal-insulator transition temperature is close to Curie temperature which decreases from 274 to 82 K as x increases from 0 to 0.17. The most important effect of Ti doping is to introduce spin clusters in the samples due to the distortion of local lattice and the inhomogeneous magnetic structure induced primarily by the random distribution of Mn ions. A maximum magnetoresistance ratio as large as 90% in 1 T at 122 K was obtained for the sample with x =0. 055, which is four times larger than that obtained for LCMO sample at 272 K. There is a remarkable field-history dependent MR in the cooling process for the doped samples while such phenomenon disappears in the warming run. The resistivity follows well the variable range hopping behavior in paramagnetic state. Both the size effect and spin dependent hopping of carriers between the spin clusters should be considered in this system.     

FeNiCrSiB非晶软磁合金薄带的巨磁阻抗效应

研究了ＦｅＮｉＳｒＳｉＢ非晶软磁合金薄带的磁性和巨磁阻抗效应。磁阻抗比ΔＺ／Ｚｓ不仅与样品的磁特性有关,而且与交变电流频率ｆ和外加直流磁场Ｈ有密切的关。对退火温度为３５０℃,退火时间为９０ｍｉｎ的样品,在交变电流频率为２ＭＨｚ下,磁阻抗比ΔＺ／Ｚｓ＝（Ｚ０－Ｚｓ）／Ｚｓ最高可达５３．７％。     

La0.67Ba0.33MnO3中Cu掺杂对电特性和室温磁电阻的影响

在溶胶-凝胶法制备的La0.47Ba0.38MnO3(LBMO)微粉中掺入CuO粉,制成一系列(LBMO)／／(CuO),(x=0．01～0．1,为摩尔比)掺杂材料,实验结果发现．随着Cu掺杂量的增加,材料的磁化强度和居里温度变化不大,材料的电阻率先快速减小,而后缓慢增大,当x=0．01时在全温范围内电阻率都达到最小值,这与Cu离子的价态变化有关。实验还发现Cu离子的掺入可以使材料的室温磁电阻逐步提高．当掺入10%的Cu时,室温磁电阻比达到-8．4％。比未掺杂的LBMO提高了50％。低电阻率导电陶瓷材料和大的室温磁电阻效应都是应用研究所关注的课题。     

MAGNETIC PROPERTIES AND RELAXATION PROCESS OF AMORPHOUS CoFeNiNbSiB SOFT MAGNETIC FILMS

用射频溅射法系统研究了非晶态CoFeNiNbSiB软磁薄膜的制备工艺,发现在0.5Pa的低氩气压下,可以得到性能优良的软磁薄膜,而且膜的性能受衬底偏压影响很小.经旋转磁场退火热处理后,膜的起始磁导率一直到10MHz都可在3000以上,表现出良好的频率特性.用电阻法研究了非晶膜在退火过程中的结构变化过程,发现高温下非晶膜明显经历了四个连续的阶段。     

Substituting Effect of Y in La0.5Ba0.5 CoO3

La0.5-xYxBa0.5CoO3 polycrystals were prepared by solid state reaction. The substituting effects of Y for La on the magnetic and transport properties of the materials were studied systematically. The results indicate that substitution of Y induces two effects. Firstly, the charge transfer from Y to 3d orbital of Co happens. This causes the molecular magnetic moment to decrease. Secondly, the antiferromagnetic exchange interaction of Co ions appears. When the content of Y is less than or equal to 30%, the non-colinear structure of spins in materials is observed. When the content of Y is greater than 30%, the materials transit from predominant ferromagnetic state to predominant antiferromagnetic one. The conductive mechanism for the materials with different content of Y belongs to the variable range hopping conduction of polarons.The resistivity of materials increases sharply with increasing Y content.     

La0.67 Ca0.33 MnO3和La0.67 Ba0.33 MnO3中Dy的置换作用

在La0.67Ca0.33MnO3和La0.67Ba0.33MnO3中用Dy对La进行了置换研究。结果发现，随掺Dy量的增加，两类材料的居里温度和金属-绝缘体相变温度单调下降，峰值电阻率单调增加。在Ca系样品中，掺入13％的Dy后，在5T的磁场下，最大磁电阻比达到7900％。在Ba系样品中．掺Dy对磁电阻的影响要小得多。掺Dy对材料性质的影响可以用晶格效应来解释，但晶格效应产生的作用与碱土离子的品种有明显关系。