AC susceptibility: a sensitive probe of interlayer coupling

Abstract The temperature-dependent AC susceptibility χ ( T ) of asymmetric perpendicularly magnetized Ni/Cu/Ni/Cu(0 0 1) trilayers is studied in situ via the polar magneto-optic Kerr effect (MOKE). The sublayer magnetizations M ( T ) and the sign and strength of the interlayer exchange coupling J inter are measured. Two maxima χ max are recorded at separate temperatures at the loss of macroscopic M of the two Ni layers for sufficiently small values of the interlayer exchange coupling J inter ≈10–100 neV/atom. With increasing J inter the χ max recorded at the lower temperature shifts progressively to higher temperatures and its intensity decreases. This change is reversed by a small external magnetic field. This shows that J inter affects χ ( T ) and M ( T ) in a similar way as an external field.