Study On The Effect Of Interfacial Mixture On The Magnetic Properties In Ferromagnetic/Anti-ferromagnetic Film

In recent years, the exchange bias effect has been widely applied in the field of the magnetic memorization, thin film magnetic and the magnetic sensor, the exchange bias effect in ferromagnetic/antiferromagnetic film is one of the foreland fields of spintronics. The exchange bias effect can beat the superparamagnetic limit in ultrahigh density media, so the study on exchange bias effect in ferromagnetic/antiferromagnetic film becomes particularly important, and it will be the foundation of developing practical applications of spintronic devices. The exchange bias in ferromagnetic/antiferromagnetic film is influenced greatly by interfacial roughness, atom mixture and dilution.In this thesis, we use the classical Heisenberg model to establish ferromagnetic (FM)/antiferromagnetic (AFM) bilayers. In this model the spins mixture at interface is taken accout. We perform Monte Carlo method to study the effects of the interface magnetic mixture, the magnetocrystalline anisotropy of antiferromagnetic layer, the exchanging interaction between ferromagnetic layer and antiferromagnetic layer, and the cooling field how to influence thermodynamic property of ferromagnetic/antiferromagnetic film. The calculation results indicate that the transformation temperature of the system will become higher, as the increasing of the interface magnetic mixture. At the same time, the peak of magnetic susceptibility and specific heat will shift right; with the impact of the cooling field, the intensity of ferromagnetic layer magnetization will become larger with the increasing of the cooling field, in antiferromagnetic layer we find a little plateaus, the intensity of the plateaus will become larger with the increasing of the cooling field.The modified Monte Carlo method in which the reversal process of spins is taken into account is used to simulate the hysteresis loops of the system. We investigate the effects of the interface magnetic mixture, the cooling field, the magnetocrystalline anisotropy of antiferromagnetic layer and the interlayer exchange interactions on the magnetization process of ferromagnetic/antiferromagnetic film. Respectively, from the simulated results, we can find that the magnetizing state of interfacial layer determines the exchange bias of the system, the interface magnetic mixture has important influence on the exchange bias and coercivity. With the increasing of the interface magnetic mixture, the exchange bias shows a trend of first increase and then decrease and a peak is founded, but the coercivity first decrease and then increase; when the cooling field is small, the net magnetization of the interfacial layer is negative and the exchange bias field is negative, when the cooling field gets to a value, the net magnetization of the interfacial layer becomes positive and the exchange bias field also becomes positive; the competition between the interfacial coupling and the cooling field is analyzed, when the cooling field is not very strong, big antiferromagnetic interface coupling will play a major role, the net magnetization of the antiferromagnetic layer is negative and the exchange bias field is negative; in addition, exchange bias field increases monotonously towards the negative direction with the increasing of the magnetocrystalline anisotropy of antiferromagnetic layer at low temperature after cooling in weak fields. The phenomena are interpreted by analyzing the energy competition among the exchanging interaction between ferromagnetic layer and antiferromagnetic layer, the magnetocrystalline anisotropy of antiferromagnetic layer, and external magnetic field in the processes of cooling and magnetizing.