Effect of pinning-field distribution on the process of magnetization reversal in Ga1−xMnxAs films

Abstract

The process of magnetization reversal in a Ga 1−x Mn x As film is investigated by using angle-dependent measurements of the planar Hall effect. When a small field (e.g., below 25 Oe) is used, the planar Hall resistance (PHR) displays four stable values arising from the formation of four different multidomain states during the rotation of the external field direction over 360 • . Two of these correspond to the sample being fully magnetized along one of the easy axes. It is shown that there are two intermediate states which form when a fraction of the domains populates one easy direction (say, [100]), and the remaining fraction populates an orthogonal easy axis (with magnetizations, say, along the [010] direction). It is further shown that the relative populations of the magnetic domains corresponding to the two orthogonal easy axes can be controlled by the value of the applied field during the process of magnetization reversal. This phenomenon can be understood by considering the differences in domain-pinning fields and their distributions required for crossing the [110] and the [110] directions in the (001) plane of the Ga 1−x Mn x As film.

Temperature Behavior of Uniaxial Anisotropy along [100] Direction in GaMnAs Films

“…To investigate the details of magnetic anisotropy in GaMnAs films, including H u2 , in this paper, we employ planar Hall effect (PHE) measurements, which are exceptionally sensitive to the effects of both the direction and strength of the external magnetic field on magnetic anisotropy parameters. 11,12) These measurements have revealed a striking asymmetry in the angular dependence of the planar Hall resistance in GaMnAs films. A careful analysis of this feature led us to identify the presence of an additional uniaxial anisotropy, H u2 , along the [100] direction.…”

Exchange bias in ferromagnetic bilayers with orthogonal anisotropies: the case of GaMnAsP/GaMnAs combination

“…(2) that when the field is swept along some direction, the values of the free energy minima change relative to one another. In particular, when the magnetization lies initially along the energy minimum in quadrant, and the energy minimum in the adjacent quadrant is made deeper by the applied field, the magnetization will switch to the lower minimum when the difference between the initial and the final minimum exceeds a domain pinning energy 23,24 . By inserting the switching fields observed for this symmetric results shown in Fig.…”

Magnetization reversal behavior of GaMnAs film grown on Si substrate investigated by planar Hall measurements

“…This observation differs from that of the GaMnAs/GaAs system, in which uniaxial anisotropy is always preferred along either the [110] or ½ 110 direction owing to the different growth dynamics at the surface of the GaAs film. 29) The second and third features are summarized in Fig. 2, which clearly shows systematic behavior with respect to the field strength.…”

“…It seems that such behavior occurs in a slightly larger field region in the GaMnAs/Si system than in the GaMnAs/GaAs system, which was investigated in Ref. 29. Because the area of the pinned domains, which do not experience a magnetization transition during the rotation of the field, is determined by the strength of the pinning field of the domains relative to that of the external field, the domain pinning field seems to be larger in the GaMnAs/Si system than in the GaMnAs/GaAs system.…”