Influence Of Buffer Layer On The Anisotropic Magnetoresistance Of NiCo Films

Materials with anisotropic magnetoresistance (AMR) can be used as the magnetic sensors which can measure the magnetic fields. Compared with other magnetic sensors such as Hall elements, semiconductor magnetoresistance elements, the AMR sensors have advantages of high sensitivity, good temperature stability and small volume. The NiCo soft alloy has larger AMR value than that of NiFe. And it can be used in the broad range of magnetic fields for its high saturation field. So investigation on the NiCo films will be helpful to extend the application of AMR sensors.Ta/Ni1-xCox (x ≈13, 17, 21 , 26, 31at%) films with different thickness have been prepared by using DC magnetron sputtering and the effect of the Co composition on the AMR value of Ni1-xCox films has been investigated. The results show that the AMR value of same thickness films reaches a maximum value at x ≈26at%, then decreases with x increases. XRD results shows that good (1 11) orientations exit in Ta/Ni74Co26 films.(Ni0.81Fe0.19)1-xCrx (45A) /Ni74Co26 (x ≈26, 30, 34, 38, 42at%) films have been prepared by using DC magnetron sputtering and the effect of the Cr composition on the AMR value of the films has been studied. The results show mat the AMR value of same thickness films reaches a maximum value at x ≈34at%, then decreases with x increases.(Ni0.81Fe0.19)66Cr34 (xA) /Ni74Co26 (200A) films have also been prepared and the effect of (Ni0.81Fe0.19)66Cr34 buffer layer thickness on the AMR value of the films has been studied. The results show that the AMR value of the films reaches a maximum value at x ≈60A, then decreases rapidly with x increases.The use of a thin (Ni0.81Fe0.19)66Cr34 buffer layer for obtaining high AMR in Ni74Co26 films is reported. The results show that the AMR value of the films deposited on a 4SA thick (Ni0.81Fe0.19)66Cr34 buffer layer is higher man that of the films deposited on Ta buffer layer. For example, an enhancement of 43% was observed for 125A Ni74Co26 films, compared to the films deposited on Ta buffer layer. XRD results show that the lattice constant of Ni74Co26 is very close to that of (Ni0.81Fe0.19)66Cr34. This would lead to the high AMR value in Ni74Co26 films.The results of the text offer a new way to increase the AMR value in NiCo films and play an important role in the practical applications.