Structure and Magnetism in Multilayer Fe/MgO/Cr/MgO/Fe Nanosystems

Layered Fe/MgO/Cr/MgO/Fe nanostructures are an artificial ferromagnetic material, in which the exchange interaction of the magnetic moments of the Fe layers through intermediate dielectric and metal layers can lead to magnetic configurations that are not implemented in well-studied Fe/MgO/Fe and Fe/Cr/Fe systems. The correlation between the structural and magnetic properties of layered nanoheterostructures Fe(10 nm)/MgO(1.5 nm)/Cr( t )/MgO(1.5 nm)/Fe(7 nm) ( t = 0.9, 1.8 nm) is studied. The data of X-ray diffractometry and high-resolution reflectometry confirm the formation of an epitaxial crystal structure and reveal its layered nature with sharp interlayer boundaries. Vibration magnetometry does not reveal substantial differences in the hysteresis loops, which have a characteristic stepped shape. Polarized neutron reflectometry makes it possible to establish that the processes of magnetization reversal in these samples occur in different ways at the level of individual Fe layers. In the sample with Cr interlayers with a thickness of 0.9 nm, the Fe layers are exchange coupled through the MgO/Cr/MgO interlayer, and their rotation is correlated upon applying a magnetic field. There is no exchange interaction between the Fe layers in the sample with a Cr interlayer with a thickness of 1.8 nm, and they undergo magnetization reversal independent of each other. It is found that the magnetization reversal of the Fe/MgO/Cr/MgO/Fe systems is characterized by an intermediate state that can be controlled using a small external field with an intensity of several tens of oersted and a change in the orientation of the sample as well as by varying the thickness of the MgO layer.