Studies On The Properties Of MgO-based Tunneling Magneto Resistance

In this paper, after a detailed analysis of the history of the development of the magnetoresistance effect, we focused on the systematic study of the output characteristics of the MgO-based tunneling magneto resistance (TMR). The papers mainly include the following three aspects:Ⅰ. TMR transfer curve and the theoretical model:We studied the working mechanism of MTJ, and tested the samples of the MgO-based TMR. Based on the principle of quantum mechanics and statistical mechanics, a new model which can precisely descript the TMR performance has been established and a function which can calculate TMR output has been given. These include:(1)TMR performance is mainly determined by the electron spin, and their behaviors obey the Fermi-Dirac distribution law;(2)Based on the principle of quantum mechanics and statistical mechanics, a new model which can precisely descript the TMR performance has been established and a function which can calculate TMR output has been given;(3)According to the model, the output, sensitivity, offset and their temperature performance can be given with analytical functions.(4)Any values about TMR output could be given analytically with our model.Ⅱ. The studies of the relationship between TMR saturation field, hysteresis and PMBased on the bias field in the perpendicular direction to the sensitivity by PM, we studied the change of TMR transfer curve in the sensitivity direction.(1) With the PM magnetic field increases, the TMR transfer curve is horizontal leveled;(2) With the PM magnetic field increases, the TMR saturation field increases approximately linear;(3) With the PM magnetic field increases, the TMR sensitivity is reduced;(4) With the PM magnetic field increases, the TMR hysteresis decreases rapidly. (5) We used the SW model to explain the impact of hysteresis by PM, and gave the approximate relationship between the hysteresis and the PM magnetic field.III.The studies of TMR temperature performanceBased on the test of MgO-based TMR samples at different temperature, using the model given in chapter I, we quantitatively studied the temperature dependence of the TMR output and established a model about TMR temperature behaviors. These include:(1) Based on the test of the TMR transfer curves at different temperature, we found that with increasing temperature, the TMR transfer curve in the overall decline, and become more "flat";(2) As the temperature increases, the TMR resistance of parallel state RP linearly decreases;(3)As the temperature increases, the TMR resistance of antiparallel state RAP linearly decreases, and faster than form;(4) As the temperature increases, the TMR, the saturation field HS increases linearly;(5) As the temperature increases, the TMR Neel coupling field HO linear decreases;(6) Functions which describe relationship between TMR parameters and temperature have been given;(7)Based on the (6) and the model in chapter I, the output of bridge under different temperature has been given;(8)Compared with the experimental results, our model is fit the test results well, which indicate that our TMR temperature model is good.