摘要:

To explore the optimized colossal magnetoresistance (MR), i.e., higher MR with lower field, magnetotransport properties of single-crystalline perovskite manganites have systematically been investigated. Nearx=1/2with intrinsic instability of charge ordering (a1/1ordering ofMn3+/Mn4+), the one-electron bandwidth (W) is varied by reducing the radius ofR-site cation inR1−xSrxMnO3.ForR=Nd,the MR behavior is rather canonical, while forR=Sm,the field-induced nonmetal-to-metal transition of the first order shows up accompanying a change in resistivity by several orders of magnitude as a result of an enhanced antiferromagnetic interaction. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119248

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A method to simultaneously determine both the wall-motion speed and the nucleation probability of magnetic films is presented, where the domain reversal patterns are modelized by time-dependent circular domains formed by the nucleation process and then, expanded by the wall-motion process. The present method has been applied to understand the contrasting reversal behaviors in the Co/Pd multilayered system and the difference in the nucleation probabilities of the samples was found to be a major origin for the observed contrasting behaviors in this system. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119249

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We investigated the reduction mechanism of surface oxide on aluminum alloy powders containing magnesium, by x-ray photoelectron spectroscopy using synchrotron radiation (SR-XPS). The reduction is the initial reaction in a new aluminum nitridation method developed by one of the authors. In heating the powders to 823 K, magnesium soluted in the powders moves from the inner region to the surface at temperatures below 573 K, and finally, above 773 K, the magnesium reduces the aluminum oxide of powder surfaces by chemical reaction, which breaks the surface oxide films, and metallic aluminum appears on the topmost surface of the powders. These results suggest that the SR-XPS system is very useful for dynamic chemical reaction analysis of the surface viain situmeasurement. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119250

出版商:AIP    

年代:1997

数据来源: AIP

ISSN:0003-6951    

DOI:10.1063/1.119251

出版商:AIP    

年代:1997

数据来源: AIP

ISSN:0003-6951    

DOI:10.1063/1.119257

出版商:AIP    

年代:1997

数据来源: AIP