Magnetization impurity effects

It was discovered by Al shits et al. (1987) that static magnetic fields of order 0.5T affect the motion of dislocations in NaCl crystals. This is not an intrinsic effect but is associated with impurities and/or radiation induced localized defects. Also, magnetic field effects have been observed in semiconductor crystals such as Si (Ossipyan et al., 2004). 

Seccand example - In the production of samariumcobalt permanent magnets impurities have practically only a dilution effect. One can therefore use instead of a 99.9 % pure samarium metal a significantly cheaper 90 %, perhaps even 80 % pure metal vdth the balance other rare earths. In any case, it is necessary in this instance that the conposition of the other rare earth elements be held constant, vdiich is not always quite so siitple. 

Magnetic structure of Ho,Ni,Pb at 5 K taking into account the impurity effect... 

The room temperature 129Xe spectra of the three carbon blacks are shown in Figure 12.17 and, surprisingly, the line width of these Xe resonances is much smaller than that of Xe in the composites. Although it is known that magnetic impurities and susceptibility effects excessively broaden the 13C line width of carbon blacks, these effects clearly are not as serious for Xe adsorbed at the outer and inner surfaces of the carbon black aggregates [20]. 

The Kondo84 effect is a scattering of conduction electrons by magnetic impurities. In the total expression for the electrical resistance R(T) of a 3D metal as a function of the absolute temperature T is given by... 

With the use of the DV-Xa molecular orbital method, electronic structure calculations have been performed to investigate the impurity effect on material properties. Firstly, calculations were done for F atoms substituted for 0 (oxygen) atoms in copper oxide superconductors. It was found that the population of the atomic orbitals of F atoms is small in HOMO (highest occupied molecular orbital) and a small fraction of charge carriers enters the impurity sites. The F impurities are therefore expected to be effective for pinning magnetic flux lines in Cu oxide superconductors. 

Partial replacements of the rare earth sites were also examined. Figure 4 shows the effect of 5% substitution of 4f ions on La sites for the La-Sr-Cu-0 system (17). The lattice parameters and Tc are plotted in the order of atomic number. Since most of these ions possess unclosed 4f orbitals, they are considered to be magnetic impurities. It is interesting to see that Tc first decreases, passes through a minimum for Gd and increases again. This suggests... 

All of the effects of replacements of each metal site so far described can be understood within a framework of a low dimensional nature of conduction mechanisms. More specifically, superconduction takes place through the O-Cu-O bonds of the interconnected CuOft octahedra or CUO4 squares in the La-Sr-Cu-0 and Y-Ba-Cu-0 systems, respectively. The La or Y sites are less sensitive for the presence of magnetic impurities and seem to be rather away from the superconduction path. This tendency is more significant in the Y-Ba-Cu-0 system, because the conduction path would be along the one dimensional chains of O-Cu-O bonds which are most apart from the Y sites. 

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