Thermoelectric Properties Of Ni-wire Nanocontact

The research of ballistic magnetoresistance for Ni nanocontacts has been inconclusive for more than a decade.Due to the nanometer-sized Ni nanocontact,there are many complex effects exist.And the truth of the experimental results is very difficult extracted and purified from the many complex phenomena under the action of the electric and magnetic fields.We found that under certain conditions the voltage across the junction was not monotonic with the current during the studying of magnetoresistance of the Ni nanocontact.The resistance increase as the temperature increase produced a parabolic R-I curve during I-V tests,which equivalent to a general resistance.The bottom of the parabolic line did not appear in the zero point of current under certain conditions.This was attributed to Peltier effect within the nanocontact.By measuring the bottom shift of parabolic line and resistance,We calculated the Peltier coefficient of the Ni nanocontact.The R-I curve of different resistance was studied under different external magnetic field.And we inducted the relationship between the Peltier coefficient,the resistance of Ni nanocontact and the external magnetic field.The Peltier coefficient was influenced by external magnetic field from two aspects:the area of the Ni nanocontact was changed due to magnetostrictive,the magnetic structure of the Ni nanocontact was changed.Seebeck effect as the inverse effect of the Peltier effect can be used to verify the authenticity of the Peltier effect.Therefore,we measured the Seebeck effect of the Ni nanocontact,qualitatively verified the Peltier effect of the Ni nanocontact.In order to remove the thermal electromotive force generated by the electrode and the nickel wire during the test process of Seebeck effect,we tested the thermoelectric effect of"(?)"-shaped nickel wire.And found its thermal electromotive force revealed magnetic anisotropy.The relationship between the thermal electromotive force of"?"-shaped nickel wire,the external magnetic field and temperature difference were discussed in detail.