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 W/Gd/W/MgO heterostructures, the dependence of mechanical stresses in the Gd film on the crystallographic orientation of the MgO substrate was revealed. Variations in the interplanar spacings in MgO in different orientations create tensile elastic stresses up to 0.22 GPa in the Gd film, which are transferred through the damping layer W. It is found that these stresses affect the isothermal magnetization curves, the corresponding change in the magnetic part of the entropy at the Curie point Tc = 293 K, and the relative cooling capacity (RCP). This allows us to consider mechanical stresses as a factor in controlling the magnetocaloric cycle, which increases the efficiency of the refrigeration machine, when mechanical loading is synchronized with the heating-cooling cycles of the ferromagnet.