In GdFeCo/Ir/GdFeCo heterostructures with amorphous GdFeCo layers, three critical points were found in the temperature dependences of the magnetization. In the neighborhood of 100 K, the temperature of compensation for the magnetizations of the Gd and FeCo sublattices is observed, which is found in the form of a magnetization minimum and does not depend on the magnetic field. As the temperature decreases, a sharp stepwise transition is observed, which corresponds to the switching of the mutual magnetization’s orientation of the GdFeCo layers between their parallel and antiparallel configurations. This transition depends on the magnetic field in which the measurement is made. Its critical temperature shifts in the range of 70–300 K with a change in the field in the range of 0.5–5 T. At low temperatures < 50 K, a transition to the spin glass state is observed, which is accompanied by a decrease in the magnetic moment to zero and disappears when the field is applied.

In synthetic ferrimagnets with perpendicular anisotropy GdFeCo/Ir/GdFeCo, the dependence of the hysteresis loops of the anomalous Hall resistance and the characteristics of the loops on the angle between the magnetic field and the plane of the sample are analyzed. The part of the anomalous Hall resistance corresponding to the spin-orbit torque has been identified. The field dependences of the resistance are sensitive to switching between the magnetic states of the two-layer ferrimagnet and they reproduce the shapes of the magnetization hysteresis loops, calculated with the interlayer exchange interaction, crystal anisotropy, and Zeeman energies at different angles between the field and sample. A slow (~30 min) magnetic relaxation of resistivity hysteresis after reorientation of the sample in magnetic field was found. Specific domain dynamics inherent in two-layer samples was revealed by Kerr microscopy. It was found that slow restoration of the resistivity hysteresis loop is due to domain propagation.