The Preparation Of The Perpendicular Magnetization Of The Spin Valve And Its Thermal Stability

Recently, with the rapid development of spintronics, the spin property of electrons have been deeply recognized and widely used in the information storage technology. This thesis focuses on the study of the perpendicularly magnetized spin valves (SVs), exchange bias effect and other related issues in spintronics. The perpendicular anisotropy of [Co/Ni] multilayer is investigated. We firstly successfully produce two kinds of perpendicular spin valves with (biased SV) and without (pseudo SV) antiferromagnetic exchange pinning layer. Then, the influence of exchange bias effect on the thermal stability of the films with perpendicular anisotropy are discussed. The main content of this thesis is as follows:The optimal condition to produce the perpendicularly magnetized [Co/Ni] multilayer structure is obtained in this thesis. We find that some factors including the thickness of Co, Ni or buffer Cu layer as well as the multialyer repetition number N affect the perpendicular anisotropy of [Co/Ni] multilayer. The strong perpendicular anisotropy can be achieved when Co and Ni are in the thickness of 0.25 and 0.59 nm, respectively. Increasing the thickness of the buffer Cu layer and repetition number could also increase the anisotropy, but too thick Cu or large N would reduce the GMR signal.We successfully produce the pseudo and FeMn-based spin valves with the perpendicularly magnetized [Co/Ni] multilayer as the free and reference layers. The GMR signal is over 7%.Furthermore, the thermal stability of the pseudo and based SVs has been discussed. We find that the GMR signal is significantly decreased for the pseudo spin valves when the annealing temperature is higher than 200 C due to the loss of the corcivity difference between the free and reference layers. In contrast, for the FeMn-based SVs, the large GMR signal could be remained until 300 C.Finally, the exchange bias effect of the pinning layer on the thermal stability has been investigated.It is found that the exchange layer could not only generate a hystersis loop shift along the field axis, but also could enhance the perpendicular anisotropy of the Co/Ni multilayer, resulting in the improvement of the GMR stability for the FeMn-biased spin valve..