Ferromagnetism of GaMnAs studied by polarized neutron reflectometry

Abstract

Polarized neutron reflectometry has been used to investigate details of spin ordering in ferromagnetic ͑FM͒ GaMnAs/GaAs superlattices. The reflectivity spectra measured below the Curie temperature reveal additional magnetic contributions to the structural superlattice Bragg peaks, clearly indicating the existence of FM interlayer correlations. Closer investigation of the magnetic reflectivity maxima using a full polarization analysis provides direct evidence that the FM order in the GaMnAs layers is truly long range. Moreover, as shown by the data, the system exhibits a strong tendency of forming a single-domain FM arrangement, even when cooled through T C in zero external field.

Spin-Dependent Phenomena in (Ga,Mn)As Heterostructures

“…In contrast, in the (Ga,Mn)As-based semiconductor ferromagnetic/ nonmagnetic systems interlayer coupling of opposite FM sign was observedby magnetic measurements [13][14][15], neutron diffraction [16], and polarized neutron reflectometry [17]. These structures differ from the previously considered EuS-based ferromagnetic semiconductor multilayers by many aspects, which all can affect the IEC.…”

“…This so-called tunnel anisotropic magnetoresistance (TAMR) effect was observed when the saturation magnetization direction was changed in-plane [9][10][11] as well as when it was turned perpendicular to the magnetic layer [11,12]. It was also shown that the magnetization vectors of consecutive (Ga,Mn)As ferromagnetic layers separated by nonmagnetic spacers in a multilayer structure are correlated by an interlayer coupling [13][14][15][16][17] and structures exhibiting giant magnetoresistance (GMR) were obtained [14].…”

Neutron scattering studies of nanomagnetism and artificially structured materials

“…Preliminary neutron reflectivity studies show long-range ferromagnetic order in (Ga, Mn)As layers across nonmagnetic GaAs spacer layers [132]. The multilayer samples exhibit distinct magnetic Bragg reflections despite the fact that the Mn content in the sample is of trace amount.…”

“…Preliminary neutron reflectivity studies of (Ga, Mn)As/GaAs multilayers indicate that thin ferromagnetic layers may interact across the nonmagnetic GaAs [132].…”

Magnetic coupling in ferromagnetic semiconductor (Ga,Mn)As/(Al,Ga,Mn)As bilayers

“…2,3 The highest Curie temperature (T C ) of this material is around 190 K. [4][5][6] The magnetic properties of (Ga,Mn)Asbased multilayers are highly tunable through manipulation of parameters such as the Mn concentration, epitaxial strain, and doping. For example, while the interlayer exchange coupling is usually ferromagnetic in (Ga,Mn)As/GaAs/(Ga,Mn)As structures, 7,8 antiferromagnetic alignment can be realized by p-type doping of the GaAs spacer. 9 Elsewhere, the coupling between compressive-strained (Ga,Mn)As and tensile-strained (Ga,Mn)(As,P) has been utilized in demonstrations of electricfield controlled magnetic anisotropy.…”