The evolution of magnetic domain structures with temperature during magnetic reversal in Co͑4 Å͒ / Pt͑t Pt ͒ multilayers with perpendicular anisotropy has been investigated using magneto-optical Kerr imaging. Relatively large Pt layer thicknesses ͑t Pt = 43 and 63 Å͒ are chosen for this study because the interlayer coupling strength in the multilayers varies from weak at room temperature to strong at low temperatures. A Co/ Pt multilayer with strong interlayer coupling ͑t Pt =11 Å͒ is also studied as a comparison. Kerr imaging during magnetic reversal shows a transformation of domain patterns with temperature which correlates directly with the enhancement of interlayer exchange coupling with decreasing temperature, as well as the conversion from domain-wall-propagation-dominant reversal at room temperature to nucleation-dominant reversal at low temperatures. The enhanced interlayer coupling at low temperatures leads to the entire multilayer switching as a single ferromagnet; while at higher temperatures, when the interlayer coupling weakens, quasi-independent layer-by-layer magnetic reversal is observed. The transformation from propagation-to nucleation-dominant magnetic reversal can be understood by the competition between activation energies for domain nucleation and propagation, Zeeman energy, and thermal energy.

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