Magnetic properties of sputtered NiFe/IrMn/Co trilayers grown on different seed layers (Cu or Ta) deposited on Si (100) substrates were investigated by magnetometry and ferromagnetic resonance measurements. Exchange bias effect and magnetic spring behavior have been studied by changing the IrMn thickness. As shown by X-ray diffraction, Ta and Cu seed layers provoke different degrees of (111) fcc-texture that directly affect the exchange bias and indirectly modify the exchange spring coupling behavior. Increasing the IrMn thickness, it was observed that the coupling angle between the Co and NiFe ferromagnetic layers increases for the Cu seed system, but it reduces for the Ta case. The results were explained considering (i) different anisotropies of the Co and IrMn layers induced by the different degree of the (111) texture and (ii) the distinct exchange bias set at the NiFe/IrMn and IrMn/Co interfaces in both systems. The NiFe and Co interlayer coupling angle is strongly correlated with both exchange bias and exchange magnetic spring phenomena. It was also shown that the highest exchange bias field occurs when an unstressed L12 IrMn structure is stabilized.
Magnetometry study of magnetron sputtered NiFe/IrMn/Co trilayers reveal that the exchange bias field at the NiFe/IrMn interface decreases with increasing NiFe layer thickness, up to 150 Å. At the IrMn/Co interface, a decrease also occurs when the NiFe layer thickness increases. Ferromagnetic resonance measurements at X and Q-band frequencies reveal that the same dependence at both interfaces, up to a 70 Å thick NiFe, is due to a spiraling interlayer coupling between the NiFe and Co layers. Unexpected increase with thicker NiFe layer is due to domain walls at the NiFe/IrMn interface in the presence of low static magnetic fields.
The magnetism at the interfacial regions of the ͓Fe͑50 Å͒ /Cr͑27 Å͔͒ 20 antiferromagnetic coupled multilayer was studied using the x-ray magnetic circular dichroism ͑XMCD͒ technique. Two experimental approaches were used to reach the interface regions. In the first one, multilayers of the same type, deposited with the Cr capping layer with different thicknesses of 30, 20, 10, and 5 Å, were analyzed and we obtained a magnetic depth profile without removing the layers. In the second approach, the layers of the sample were thinned by several in situ sputtering cycles with Ar + ions, followed by XMCD analysis. We found a strong reduction of the Fe spin magnetic moments in the sputtered sample, which was caused by the erosion of the layers. On the contrary the noneroded samples kept the Fe bulk moment values. The observation of Cr XMCD signal evidenced an induced moment on Cr antiparallel to the Fe moments.
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