| The giant magnetoresistance (GMR) of melt-spun Cu-Co alloys is similar with magnetic multilayer film that the current direction is perpendicular to the surface of the film (CPP), it result from mainly the spin-dependent scattering of the conduction electrons against the magnetic particles and the interface between the magnetic particles and the nonmagnetic matrix. GMR can be affected by the structure parameters of the magnetic particles, such as the size, distribution, interface roughness, crystal defects and impurities in the alloys, in which the effection of the size and distribution of the magnetic particles are most remarkable. The giant magnetoresistance can be improved by change the alloy's microstructure, which can be controlled by changing heat treatment conditions. It is also found that the GMR can be improved by doped a certain amount of Ni in Cu-Co alloy.Since the GMR of Cu-Co alloy ribbons was found, many relative researches were performed. They mainly concentrated their attention on the works of the Cu-Co alloy, including the magnetoresistance at circumstances of room temperature and low temperature; TEM reaserches for the sample surface; and the element content reaserches in the different regions of the samples by EDS with the TEM, and so on. However, we have not founnd the report about the effect of the temperature in the region between the room temperature and the high temperature on resistance and magnetoresistance. We also have not founnd the report about the effect of the Co content on the magnetoresistance of Cu/Co/Ni alloy. Therefore, in this paper we investigate the following problems:(1) We prepared melt-spun Cu95-xCo)xNi)5 (x=0,7,13,15,19,25,31) ribbons to study Co content influence of the GMR. We found that the Cu95-xCoxNi5 (x=0,7,13,15,19,25,31) ribbons possess a single fcc phase, its crystal lattice is bigger than Ni, a little smaller than Cu. There are many small particles which diameter size is about 10 - 20 nm on the sample surface. The content of Co in the grain region is higher than that of grain-free region. It means that Cu-Co-Ni alloy was formed, but the distribution of the Co elements in the sample was not uniform. Co content in the grain region is higher than in the background region.The resistivity of the sample increases almost-linearly with the temperature increasing. The resistivity increase the Co content increasing, when the cobalt content x≤25%。However, The resistivity with x=31% is a little smaller than x=25%. The magnetoresistance of the all most of sample is increases approximate linearly with the temperature increasing. The magnetoresistance reached maximize when the cobalt content x= 13%, it reached 2.12% when the measurement temperature is at 300K, and it reached 6.13% when the temperature is at 375K.(2) The influence of the heat treatment temperature on the magnetoresistance of the melt-spun ribbon samples Cu80Co15Ni5 + Nd was investigated, after the samples were heat treated for 1 hour in the low vacuum at the the temperature from 300℃to 700℃.The special saturation magnetizationσS of all of the samples are close each other, except the sample after heat treatment at 400°C, which is obviously greater than other samples, including the sampls after heat treatment at other temperature and before heat treatment.When the heat treatment temperature is at 300°C and 400°C, the resistivity of the samples is 4 to 5 times of the sample before heat treatment. The changing rate of resistivity with the temperature increase slightly. When the heat treatment temperature is at 500°C and 600°C, the resistivity of the samples is about 7 times of the sample before heat treatment. The change rate of resistivity with the temperature increases further.There is no obvious influence of annealling treatment on magnetoresistance near the room temperature. However, there is obvious influence of annealling treatment on the change rate of magnetoresistance with the temperature. When the annealling treatment is in the region between 400°C～600°C, the magnetoresistance increases with the temperature increasing. When the heat treatment temperature is at 400°C, its GMR can reach 8.7% at mesurement temperature of 367K. When the annealling treatment is at 600°C, there is no obvious change of the magnetoresistance with the the measurement temperature, GMR of the sample increases only from 1.58% to 1.62%, when the measurement temperature increases from 292K to 367K.(3) The influence of doping different rare earth elments on the magnetoresistance of Cu80Co15Ni5 alloy.There are the differences of lattice parameter of the samples with doping different rare earth elements, which results from the sort and content of the rare earth elements.The saturated magnetizing field of the sample can be redued with doping rare earth elments, which is advantageous to expand the field of the sample application.There are the different effects of doping different rare earth on the magnetoresistance of the samples: doping rare earth Nd can enhance the sample`s magnetoresistance in room temperature, and doping rare earth La, Ce can enhance the sample`s magnetoresistance in the high temperature. |
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