Magnetization reversal and anomalous dependence of the coercive field with temperature in MnAs epilayers grown on GaAs

Abstract

The magnetic properties of MnAs epilayers have been investigated for two different substrate orientations: GaAs(100) and GaAs(111). We have analyzed the magnetization reversal under magnetic field at low temperatures, determining the anisotropy of the films. The results, based on the shape of the magnetization loops, suggest a domain movement mechanism for both types of samples. The temperature dependence of the coercivity of the films has been also examined, displaying a generic anomalous reentrant behavior at T>200 K. This feature is independent of the substrate orientation and films thickness and may be associated to the appearance of new pinning centers due to the nucleation of the β-phase at high temperatures.

Fast domain wall dynamics in MnAs/GaAs films

“…1, inset) shows a characteristic increase similar to that of Ref. 18. At 200 K, the MnAs film exhibits a single α-phase structure.…”

“…At 200 K, the MnAs film exhibits a single α-phase structure. The progressive nucleation of the β phase is initiated above 200 K. It remains an unordered phase up to 280-290 K, beyond which it adopts a self-organized stripe pattern, leading to a strong increase of the coercive field [18,28].…”

Stripes in thin ferromagnetic films with out-of-plane anisotropy

“…1,2,3,4,5,6,7,8 Such films possess several magnetic phases in which the magnetization can be uniformly normal to the plane, canted, or periodically modulated in one direction (striped). Magnetization curves exhibit intricate magnetic hysteresis indicating coexistence of phases.…”

Magnetostructure of MnAs on GaAs revisited

“…This was done with the 120 nm thick film. Analysis of all four component images gave tilt angles of Ā of about 40° to the film normal and to the magnetic easy axis of the FM stripes ( [11][12][13][14][15][16][17][18][19][20]). The small XMLD signal and signal-to-noise level in the difference images of the 120 nm thick film cause a large uncertainty in these values, so that they should be considered as preliminary.…”

“…13 Most of the work on the epitaxial MnAs film, however, was concentrated on the ferromagnetic α phase, which is now well understood, mainly due to the many multimethod studies of the Däweritz/Ploog group as documented in an extensive recent review by Däweritz. 14 In nearly all of this work including a very recent study 15 the β phase was considered to be paramagnetic. Only recently, stimulated by the theoretical work to be discussed next, experiments have been interpreted as supporting an AFM β phase.…”