Growth and Magnetic Oscillatory Exchange Coupling of Mn/Fe(001) and Fe/Mn/Fe(001)

The magnetic ordering and the interlayer exchange coupling in Mn and Fe/Mn wedge structures grown epitaxially on Fe(001) whisker substrates were investigated using scanning electron microscopy with polarization analysis (SEMPA). In bare Mn/Fe(001) samples, the magnetization of the top Mn layer is collinear with the Fe magnetization, and oscillates between ferromagnetic and antiferromagnetic alignment as the Mn thickness increases. The period of the oscillation is two layers of Mn, consistent with the growth of an antiferromagnetic Mn wedge. The bare Mn behaves very much like antiferromagnetic Cr, however the magnetic coupling in the Fe/Mn/Fe(001) sandwich structures is very different. For Mn thicknesses greater than four layers, the coupling between the top Fe layer and the Fe whisker substrate is not collinear. Between 4 to 8 layers of Mn, the direction of the top Fe in-plane magnetization lies at an angle of 60° to 80° relative to the magnetization of the Fe substrate. Beginning at the 9 Mn layer, the direction of the coupling oscillates, with a 2 layer period, between 90 φ and 90 + φ, where φ is sample dependent. Values of φ between 10° to 30° were observed.