Identifying the character of ferromagnetic Mn in epitaxial Fe/(Ga,Mn)As heterostructures

Abstract

We demonstrate that the growth of Fe/͑Ga,Mn͒As heterointerfaces can be efficiently controlled by epitaxy and that robust ferromagnetism of the interfacial Mn atoms is induced at room temperature by the proximity effect. X-ray magnetic circular dichroism and x-ray resonant reflectivity data, supported by theoretical calculations, were used to monitor both temperature and magnetic field dependence of the Mn magnetic moment in the semiconducting host. We identify distinct Mn populations, each of them with specific magnetic character.

Reorientation transition of the magnetic proximity polarization in Fe/(Ga,Mn)As bilayers

“…4(d)] and one order of magnitude smaller for Fe/30 nm (Ga,Mn)As with 6% Mn. The evidence of ferromagnetic exchange bias is seemingly in contrast to our observation of an antiparallel alignment (thickness (Ga,Mn)As 15 nm) of the two layers at the interface 12,13 and to the observation of an antiferromagnetic exchange bias effect in recent SQUID measurements of Fe/(Ga,Mn)As bilayer samples.…”

“…The presence of a clear Mn magnetic signal at room temperature indicates that a small part of the (Ga,Mn)As layer, located at the interface, exhibits ferromagnetic order due to the proximity effect of the Fe layer, as already observed in previous experiments. [12][13][14] In Fig Even though the magnitude and the shape of the XMCD of Fe and Mn is in perfect agreement with previous studies the sign of the coupling between the Fe and Mn is opposite to the one observed so far. In fact, an antiparallel alignment has always been observed at the Fe/(Ga,Mn)As interface, while the up-down feature of the XMCD of Fe and Mn in Figs.…”

“…At the interface within a thin layer (d ≈ 1-2 nm) the magnetization of GaMnAs is aligned antiparallel to the Fe magnetization up to a field of 50 kOe, as it was deduced from recent measurements. 12,13 Subsequently, the magnetization of the (Ga,Mn)As is free to rotate toward the global easy axis of (Ga,Mn)As. In the presence of a cubic and uniaxial anisotropy the direction of the bulk (Ga,Mn)As easy axis with respect to the [110] direction is given by (the other easy axis is located symmetrically with respect to the [110] direction):…”

“…In the Fe/(Ga,Mn)As system, the Fe overlayer induces a proximity polarization antiparallel to the Fe moment within a 1-2 nm (Ga,Mn)As region, which is promising for improving the ferromagnetic properties of very thin (Ga,Mn)As films. [12][13][14] In fact, we have recently demonstrated that the proximity effect effectively enhances the operation temperature of Fe/(Ga,Mn)As hybrid spin injection devices when very thin (Ga,Mn)As injector and detector contacts are capped by an iron layer. 15 However, to take full advantage of the control of the magnetization of the (Ga,Mn)As injector/detector contacts, it is of importance to understand the coupling mechanism in this epitaxial FM metal/DMS bilayer system.…”

Thickness-dependent magnetic properties of oxygen-deficient EuO

“…This is due to the enhanced, conduction-electron-mediated RKKY coupling between the Eu 4f spins [8,9]. In thin films and interfaces these fundamental magnetic properties can also be influenced by additional factors, such as surface-induced modification of the crystalline environment and of the band structure [10] as well as magnetic proximity effects [11][12][13]. These interface effects have been studied experimentally mainly in 3d systems, be they itinerant ferromagnets [10] or transition metal oxides [14,15], while interfaces of the 4f compound EuO have only been analyzed theoretically [16,17].…”