Single and multidomain characteristics of GaMnAs investigated by magnetotransport measurements

Abstract

We have investigated the magnetization reorientation process of GaMnAs ferromagnetic films by changing external field direction in planar Hall effect (PHE) measurement. While the angular dependences of PHE data taken with clockwise and counterclockwise under strong magnetic field (i.e., above 400Oe) are completely overlapped without hysteresis, they are significantly different under small magnetic field (i.e., below 50Oe) by exhibiting nonabrupt hysteresis. We have analyzed such angular dependence of PHE using the magnetic free energy based on Stoner-Wohlfarth model. The behavior observed under the high field was well understood in terms of coherent rotation of magnetization in the form of single domain. However, the nonabrupt hysteric behavior observed with low field cannot be explained by a single domain picture and requires involvement of multidomain structures.

Distribution of magnetic domain pinning fields inGa1−xMnxAsferromagnetic films

“…The details regarding growth, annealing, and sample preparation are described elsewhere. 18 Curie temperatures T C of 62 and 136 K were estimated for the as-grown and annealed films from the temperature dependences of their respective resistivities. Planar Hall-effect ͑PHE͒ measurements revealed the magnetic easy axes lying in the layer plane in both samples but the magnetic anisotropy within the plane obtained from the angular dependence of PHE is found to be quite different in the two cases.…”

Interface exchange coupling induced fourfold symmetry planar Hall effect in Fe3O4/NiO bilayers

“…α M and α H are angles of magnetization and external magnetic field direction with respect to the current direction (along [100] axis). By using the relation R PHR ¼ ðk=tÞM 2 sin 2α M [14], the α M Àα H curves (not shown) were obtained from the PHRÀ α curves measured in Fig. 3(b) and (d).…”

“…In addition, since the magnetization direction is determined by the competition between the external magnetic field and the magnetic anisotropy of the system, the PHE provides a powerful tool to study the in-plane magnetization rotation [9][10][11][12][13]. The typical example is the presence of strong cubic anisotropy in GaMnAs, resulting in four easy directions in the system [14][15][16][17][18]. Although giant magnetoresistance in the exchange bias based spin valves is fully understood, the effect of exchange coupling at the interface of FM/AFM on the anisotropic magnetotransport in FM layer is still lack of exploration, especially for PHE.…”

Coexistence of magnetic domains with in-plane and out-of-plane anisotropy in a single GaMnAs film

“…Since the second and third terms in Eq. (1) rely on the normal and in-plane components of magnetization, the Hall effect measurements can be used to study the details of magnetic anisotropy of the ferromagnetic film [20][21][22]. The planar Hall resistance (PHR) data taken at 3 K with several different orientations of the external magnetic field within the film plane are shown in Fig.…”