Enhancement of Curie temperature in Ga1−xMnxAs epilayers grown on cross-hatched InyGa1−yAs buffer layers

Maksimov, O.; Sheu, B. L.; Xiang, Gang; Keim, Nathan C.; Schiffer, P.; Samarth, N.

doi:10.1016/j.jcrysgro.2004.05.091

Cited by 7 publications

(5 citation statements)

References 21 publications

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“…Full details of the sample growth by molecular beam epitaxy and post-growth annealing procedures are described elsewhere. 14 The anomalous magneto-transport behavior discussed in this paper is generic to all the samples studied (both as-grown and annealed). We present data from two annealed samples (A and B) and one as-grown sample (C) with T C = 135K, 130K and 125K, respectively.…”

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confidence: 76%

Magnetoresistance anomalies in (Ga,Mn)As epilayers with perpendicular magnetic anisotropy

et al. 2005

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We report the observation of anomalies in the longitudinal magnetoresistance of tensile-strained Ga 1−x Mn x As epilayers with perpendicular magnetic anisotropy. Magnetoresistance measurements carried out in the planar geometry (magnetic field parallel to the current density) reveal "spikes" that are antisymmetric with respect to the direction of the magnetic field. These anomalies always occur during magnetization reversal, as indicated by a simultaneous change in sign of the anomalous Hall effect. The data suggest that the antisymmetric anomalies originate in anomalous Hall effect contributions to the longitudinal resistance when domain walls are located between the voltage probes. This interpretation is reinforced by carrying out angular sweeps of H, revealing an antisymmetric dependence on the helicity of the field sweep.

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confidence: 76%

Magnetoresistance anomalies in (Ga,Mn)As epilayers with perpendicular magnetic anisotropy

et al. 2005

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“…The width of the unreversed stripe domains is a few microns, which is much wider than the typical domain wall width (~15 nm) in (Ga,Mn)As [20]. The anisotropic magnetization reversal process may be attributed to an anisotropy of residual pinning sites after annealing [21], or to uniaxial in-plane magnetocrystalline anisotropy [22]. devices are determined by using PMOKM to be 120±2 K and 122±2 K, respectively.…”

Section: Magnetization Reversal In Thin Filmmentioning

confidence: 98%

Magnetic reversal under external field and current-driven domain wall motion in (Ga,Mn)As: influence of extrinsic pinning

et al. 2008

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We investigate the anisotropy of magnetic reversal and current-driven domain wall motion in annealed Ga 0.95 Mn 0.05 As thin films and Hall bar devices with perpendicular magnetic anisotropy. Hall bars with current direction along the [110] and ] 0 1 1 [ crystallographic axes are studied. The [110] device shows larger coercive field than the ] 0 1 1 [ device. Strong anisotropy is observed during magnetic reversal between [110] and ] 0 1 1 [ directions.A power law dependence is found for both devices between the critical current (J C ) and the magnetization (M), with J C ∝ M 2.6±0.3 . The domain wall motion is strongly influenced by the presence of local pinning centres. Introduction(Ga,Mn)As, a model ferromagnetic semiconductor [1], has attracted much attention for fundamental physics and for its potential applications in spintronics [2,3]. Its magnetic anisotropy is dominated by magnetocrystalline effects which are dependent on carrier density and strain, in good agreement with theory [2]. (Ga,Mn)As epilayers grown on a relaxed (001) (In,Ga)As buffer layer experience a tensile strain due to the difference in lattice constant in each layer. Under these conditions the magnetic easy axis is perpendicular to the plane [4]. Stripe domain patterns in (Ga,Mn)As with perpendicular magnetic anisotropy have been observed previously using scanning Hall probe microscopy [5] and polar magnetooptical Kerr effect microscopy (PMOKM) [6,7,8,9]. The stripe domains are formed with a typical width of a few microns at low temperatures [5], and may be influenced by low temperature annealing [6,7,9].It has become clear that implementation of spintronics for memory applications requires the ability to manipulate the magnetic state of a material through the application of electric fields. Manipulation of magnetic domain walls using a spin-polarized current offers a key route to this. Currentdriven domain wall motion in both ferromagnetic metals and semiconductors has been demonstrated, but the mechanism is still under debate [10,11,12]. The critical current density for domain wall motion is predicted to be proportional to the saturation magnetization [13,14], which is typically two orders of magnitude smaller in (Ga,Mn)As than that in transition metal ferromagnets. The heating effect and the Oersted field produced by the critical current is correspondingly lower, so that (Ga,Mn)As is one of the best candidates for understanding current-driven domain wall motion.Previous studies of current-driven domain wall motion in (Ga,Mn)As obtained critical current densities of around 10 5 A/cm 2 , which is much smaller than typically reported values for metal films. These studies were performed on films of thickness around 25 nm, with either in-plane [15] or perpendicular-toplane easy magnetic axes [16]. In contrast, for studies of thicker (150 nm) films with in-plane magnetic easy axes, no evidence of current-driven domain wall motion was observed [17].In the present work, we concentrate on the domain images in magnetic reversal and current-drive...

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“…[5] (7.3 µm × 7.3 µm), and show a clear correlation between magnetic and topographic features. These images reveal that, at the lowest temperatures the magnetic stripe domains are aligned along the topological crosshatch pattern, known to form along the <110> directions due to mismatch dislocations in the buffer layer [ 9,10]. This indicates that an additional mechanism, besides the magnetocrystalline anisotropy, is responsible for determining the size and direction of the magnetic stripe domains during magnetization reversal at low temperatures.…”

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confidence: 87%

“…Above about 20K, thermal excitation is sufficient to overcome the energy barriers at these pinning sites and the stripe domain pattern is not observed. Recently, it has been proposed [10] that it may be energetically favourable for the interstitial Mn atoms to be concentrated at the ridges of the crosshatch pattern. Alternatively, the misfit dislocations may provide more favourable sites for Mn interstitials in the trough regions.…”

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confidence: 99%

Domain imaging and domain wall propagation in (Ga, Mn)As thin films with tensile strain

Wang

Rushforth

Grant

et al. 2007

Journal of Applied Physics

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We have performed spatially resolved Polar Magneto-Optical Kerr Effect Microscopy measurements on as-grown and annealed Ga 0.95 Mn 0.05 As thin films with tensile strain.We find that the films exhibit very strong perpendicular magnetic anisotropy which is increased upon annealing. During magnetic reversal, the domain walls propagate along the direction of surface ripples for the as-grown sample at low temperatures and along the [110] direction for the annealed sample. This indicates that the magnetic domain pattern during reversal is determined by a combination of magnetocrystalline anisotropy and a distribution of pinning sites along the surface ripples that can be altered by annealing. These mechanisms could lead to an effective method of controlling domain wall propagation.

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Enhancement of Curie temperature in Ga1−xMnxAs epilayers grown on cross-hatched InyGa1−yAs buffer layers

Cited by 7 publications

References 21 publications

Magnetoresistance anomalies in (Ga,Mn)As epilayers with perpendicular magnetic anisotropy

Magnetoresistance anomalies in (Ga,Mn)As epilayers with perpendicular magnetic anisotropy

Magnetic reversal under external field and current-driven domain wall motion in (Ga,Mn)As: influence of extrinsic pinning

Domain imaging and domain wall propagation in (Ga, Mn)As thin films with tensile strain

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