Study on spin-valve type multi-value memory using spin glass/ferromagnetic exchange coupled thin film

点击翻译按钮获取中文摘要

Magnetic anisotropy and the magnetic phase transition temperature in reentrant spin glass NiMn/Cu multilayer and NiMn/Cu/Ni trilayer films were investigated to fabricate a spin valve type memory. For the trilayer film, the field dependent magneto-resistance was measured to discuss the possible contribution from the giant magneto-resistance (GMR) effect.NiMn/Cu multilayer and NiMn/Cu/Ni trilayer film were prepared using the Ar ion-beam sputtering method in an ultra high vacuum chamber. The magnetic anisotropy was estimated using a superconducting quantum interference device (SQUID) magnetometer.The magnetic phase transition temperatures decrease with decreasing the film thickness in NiMn/Cu multilayer sample. When the sample was annealed, however, the ferromagnetic phase transition temperature increased. This indicates that the ferromagnetic magnetization of the annealed NiMn sample is maintained up to a higher temperature compared with the non-annealed sample. In addition, the magnetic anisotropy field was analyzed as a function of the thickness of the Cu layer in the trilayer sample. As a result, we found that a magnetic coupling between NiMn and Ni layers becomes pronounced when the thickness of Cu layer is thinner than a thickness between 30 and 59 AィイD4゜ィエD4. This is an important information to fabricate the GMR trilayer film in which the decoupling between the magnetic layers is required. The GMR effect could not be confined because the contribution from the anisotropic magneto resistance is significant in the trilayer sample, due to the small difference of the resistance among the three layers.