Aftereffect measurements have been performed on synthetic ferrimagnets showing strong perpendicular magnetic anisotropy, namely (Co/Pt)/Ir/(Co/Pt), by measuring the magnetization of the sample as a function of time for several different applied magnetic fields. Unexpected magnetic relaxation has been observed. Indeed, for some particular applied magnetic fields, the magnetization as a function of time first plummets and then increases. This nonmonotonic aftereffect can be understood by considering the possible magnetic states and the transitions between those states. This understanding has been confirmed and detailed using magneto-optical Kerr effect (MOKE) microscopy. Indeed, the measurements show nucleation and propagation of a transient metastable magnetic configuration. Furthermore, we were able to obtain a good qualitative agreement between a simple one-dimensional model and the experimental observation. We could strongly support the hypothesis that this peculiar nonmonotonic behavior could be a very general feature that should be observed in any antiferromagnetically coupled system (synthetic ferrimagnets, synthetic antiferromagnets) with perpendicular magnetic anisotropy.
Bibliographical noteFunding Information:
H.S.T. thanks the Peruvian Doctoral Scholarship Program of CIENCIACTIVA (CONCYTEC) for financial support under Grand No. 218-2014-FONDECYT. J.Q.-M. and C.V.L. are grateful to CIENCIACTIVA (CONCYTEC) for financial support through the Excellence Centers Program. C.H.W.B. acknowledges financial support from EPSRC (Grant No. EP/J00412X/1). R.M. thanks to Institute Jean Lamour Nancy for financial support of visiting professorship. This work was supported by Ministry of Education and Science of the Russian Federation (grant 3.1992.2017/4.6). This work was also partly supported by the French PIA project “Lorraine Université d’Excellence,” reference ANR-15-IDEX-04-LUE. by the ANR-NSF Project, ANR-13-IS04-0008-01, COMAG. This work was also partly funded by the ANRT, under the CIFRE convention No. 2016/1458.
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