Magnetic interlayer coupling and magnetization switching characteristics have been investigated in synthetic antiferromagnetically coupled [Pt/CoFeB]N1/Ru/[CoFeB/Pt]N2 structures with perpendicular anisotropy. We observe an oscillatory behavior of the antiferromagnetic coupling with a period of 0.7 nm and a maximum coupling strength of 0.09 erg/cm2. The coupling field is shown to decrease rapidly with the increase of repetition number and measurement temperature. Depending on the repetition numbers of the two multilayers, magnetic hysteresis loops may or may not display a reversal feature of the net magnetic moment. Samples with large N have a bow-tie loop shape due to the formation of multi-domains. The analysis of magnetic moments and exchange coupling fields show that there exists a ∼0.4 nm thick magnetic dead layer mostly at the CoFeB/Ru interface.
Bibliographical noteFunding Information:
This work was supported by the National Natural Science Foundation of China (Grant Nos. 51222103, 11274113, 11074046, 51171047, and 61078030), and the National Basic Research Program of China (2009CB929201). Zhang thanks for the support from the Program for New Century Excellent Talents in University (NCET-12-0132). B. Ma thanks for the support from the NSFC (Grant Nos. 51071046 and 11174056).
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