Magnetic Domain Structure and Magnetic Anisotropy inGa1−xMnxA

Abstract

Large, well-defined magnetic domains, on the scale of hundreds of micrometers, are observed in Ga1-xMn(x)As epilayers using a high-resolution magneto-optical imaging technique. The orientations of the magnetic moments in the domains clearly show in-plane magnetic anisotropy, which changes through a second-order transition from a biaxial mode (easy axes nearly along [100] and [010]) at low temperatures to an unusual uniaxial mode (easy axis along [110]) as the temperature increases above about T(c)/2. This transition is a result of the interplay between the natural cubic anisotropy of the GaMnAs zinc-blende structure and a uniaxial anisotropy which attribute to the effects of surface reconstruction.

High domain wall velocities in in-plane magnetized (Ga,Mn)(As,P) layers

“…For the subsequent DWP study, the field was therefore aligned along the easy axis of the sample, as well as with the Kerr axis. This configuration led to the observation of 180 • charged DWs, as reported previously 20,21 . The layers were kept unpatterned to understand how the complex in-plane anisotropy of the material interplays with its uniaxial anisotropy in fieldinduced DW dynamics.…”

Spin-orbit coupling effect in (Ga,Mn)As films: Anisotropic exchange interactions and magnetocrystalline anisotropy

“…[11][12][13][14][15][16][17][18] In spite of different experimental conditions, the in-plane uniaxial anisotropy was observed for (Ga,Mn)As films in a thickness range from 25 nm (Ref. 20) to 500 nm, 16 irrelevant with respect to the surface condition.…”

“…So far, however, to the best of our knowledge, there is no consensus in the literature concerning the origin of the in-plane uniaxial anisotropy. Although in some recent theoretical works the origin of the uniaxial in-plane anisotropy is attributed to a trigonal distortion caused by a uniaxial or shear strain within the film plane, 13,18,21 this type of distortion was not observed experimentally. Recently, Werpachowska and Dietl 22 suggested that the anisotropy mechanism in (Ga,Mn)As films originates from Dzyaloshinsky-Moriya interactions, without assuming any in-plane lattice distortion within their model.…”

“…[1][2][3] In the latter case the spin-orbit coupling (SOC) makes the valence states close to E F sensitive to lattice distortions and is in that way responsible for the in-plane MCA due to compressive strains originating from the lattice mismatch between the (Ga,Mn)As film and GaAs substrate. [7][8][9][10][11][12][13][14][15][16][17] As soon as the spin polarization of the valence bands becomes rather small, the MCA in (Ga,Mn)As is discussed in terms of anisotropic exchange interactions of the Mn atoms. 2,3,7 The strength of the MCA depends on the hole concentration introduced by the Mn impurity atoms 2, 11,18,19 as well as on the variation of the equilibrium lattice parameter of (Ga,Mn)As, which increases with increasing Mn content and results thus in a larger lattice mismatch with the GaAs substrate.…”

Advances in magneto‐optical imaging applied to rock magnetism and paleomagnetism

“…These merits suggest that the MOI technique can be very helpful to identify minerals carrying a magnetic moment in geological samples. The technique is, in fact, already widely used in material science for the observation of magnetic domain structures in magnetic materials [Polyanski et al, 1999;Welp et al, 2003] or flux penetration in superconductors [Dorosinskii et al, 1992;Jooss et al, 2002]. This technique has also been recently applied to geological samples [Bobyl et al, 2007].…”