Gang JI
,
Shishen YAN
,
Yanxue CHEN
,
Qiang CAO
,
Wei XIA
,
Yihua LIU
,
Liangmo MEI
,
Ze ZHANG
,
null
材料科学技术（英文）
2×(FeNi/CoZnO)/ZnO/(CoZnO/Co) ×2 spin-injection devices were prepared by sputtering and photo-lithography. In the devices, two composite magnetic layers 2×(FeNi/CoZnO) and (CoZnO/Co) ×2 with different coercivities were used to fabricate the ZnO-based semiconductor spin valve. Since the CoZnO ferromagnetic semiconductor layers touched the ZnO space layer directly, the significant spin injection from CoZnO into ZnO was observed by measuring the magnetoresistance of the spin-injection devices. The magnetoresistance reduced linearly with increasing temperature, from 1.12% at 90 K to 0.35% at room temperature.
关键词:
Spin injection
,
磁电阻
,
铁磁性半导体
Baoxin HUANG
,
Yihua LIU
,
Ruzhen ZHANG
,
Chengjian WANG
,
Gang JI
,
Liangmo MEI
材料科学技术（英文）
The Gd substituting effects for La in La0.67Ca0.33MnO3 has been studied. With increasing the substituting amount of Gd, the phase transition temperature of metal-isolator for the samples decreases, the corresponding peak resistivity increases,the Curie temperature decreases monotonically. The substitution of La-Ca-Mn-O with 11% Gd for La improved the magnetoresistance ratio by an order of magnitude. The effects of substituting Gd can be explained in terms of the lattice effects. An irreversible MR behaviour was observed in Gd-substituting compounds. This effect became marked when the substituting amount of Gd was greater than 7%. A maximum irreversible increment of MR ratio as large as 91% was obtained when Gd substituting amount was 11%.
关键词:
Manganese perovskites
,
null
,
null
,
null
Yanxue CHEN
,
Shouguo WANG
,
Liangmo MEI
,
Kungwon Rhie
,
Sangjin Byeun
材料科学技术（英文）
A series of CoFe (4 nm)/ Cu(X nm) Al (Y nm)/ CoFe(6 nm) samples have been prepared at room temperature. An exponential decay of the GMR (Giant Magnetoresistance) with Y was observed for fixed X=2nm. The characteristic decay parameter of Al is obtained to be about 0.26nm, which is rather close to 1 monolayer for Al. A coexistant state of GMR and AMR (anisotropic magnetoresistance) was observed when Y=2 nm. As the Cu spacer is replaced by Al layer, only AMR effect dominates. The experimental data further underline the important role played by the nonmagnetic spacers.
关键词:
CoFe
,
null
,
null
Li CHEN
,
Hua LI
,
Liangmo MEI
材料科学技术（英文）
The electronic structures of new superconducting perovskite MgCNi3 and related compounds MgCNi2T (T=Co, Fe, and Cu) have been studied using MS-Xα method. In MgCNi3, the main peak of density of states is located below the Fermi level and dominated by Ni d. From the results of total energy calculations, it was found that the number of Ni valence electron decreases faster for the Fe-doped case than that for the Co-doped case. The valence state of Ni changes from +1.43 in MgCNi2Co to +3.02 in MgCNi2Fe. It was confirmed that Co and Fe dopants in MgCNi3 behave as a source of d-band holes and the suppression of superconductivity occurs faster for the Fe-doped case than that for the Co-doped case. In order to explain the fact that Co and Fe dopants in MgCNi3 behave as a source of d-band holes rather than magnetic scattering centers that quench superconductivity, we have also investigated the effects of electron (Cu) doping on the superconductivity and found that both electron (Cu) doping and hole (Co, Fe) doping quench superconductivity exist. Comparing with the hole (Co) doping, there was no much difference between Cu and Co doping. This suggests that Co and Fe doping do not act as magnetic impurity.
关键词:
Electronic structure
,
null
,
null
