Magnetization Reversal Process Study in Exchange Coupled Synthetic Antiferromagnetic Multilayers and Patterned Structures

FeCo/Ru/FeCo exchange coupled synthetic antiferromagnetic (SAF) multilayers were prepared with two sputtering modes. One is continuous sputtering mode and the other is layer-by-layer sputtering mode. The former mode implies that the growth of the entire FeCo layer has no intervals, while the latter implies that the growth of the entire FeCo has many intervals. It is found that the exchange coupling filed H_ex of sample sputtered by layer-by-layer mode is higher than the one sputtered by continuous mode. Magnetic properties of samples deposited by layer-by-layer mode were studied versus sputtering power. We can conclude that the bilinear exchange constant increases and the biquadratic exchange constant decreases with the increase of the sputtering power. The magnetization reversal process was studied by the magnetic force microscopy (MFM) measurement. We can get that the magnetization reversal process is a domain-wall move process. When the applied magnetic filed is smaller than H_ex, both the two magnetic layers have same domain structure and the domain structure of the two layers are reverse correspondingly. It is also found that when the applied field is smaller than H_ex and changing, the domain wall of the two layers move correspondingly at the same time. From MFM measurement of exchanging coupling square elements, we can conclude that the single domain size of SAF multilayers is larger than 5 μm when the applied magnetic field is smaller than the H_ex.