Epitaxial GaMnAs layers and nanostructures with anisotropy in structural and magnetic properties

Wenisch, J.; Ebel, L.; Gould, C.; Schmidt, G.; Molenkamp, L. W.; Βrunner, Karl

doi:10.1016/j.jcrysgro.2006.11.312

Cited by 5 publications

(4 citation statements)

References 7 publications

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“…However, we have been able to verify that strain relaxation is the important agent in the effects reported here using x-ray diffraction measurements on long and narrow etched (Ga,Mn)As stripes [16].…”

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confidence: 63%

Lithographic engineering of anisotropies in (Ga,Mn)As

Hümpfner

Pappert

Wenisch

et al. 2007

Applied Physics Letters

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The focus of studies on ferromagnetic semiconductors is moving from material issues to device functionalities based on novel phenomena often associated with the anisotropy properties of these materials. This is driving a need for a method to locally control the anisotropy in order to allow the elaboration of devices. Here we present a method which provides patterning induced anisotropy which not only can be applied locally, but also dominates over the intrinsic material anisotropy at all temperatures.The coupling of transport and magnetic properties in ferromagnetic semiconductors gives rises to many interesting anisotropy related transport phenomena such as strong anisotropic magnetoresistance (AMR), inplane hall [1], tunneling anisotropic magnetoresistance (TAMR) [2,3] and Coulomb blockade AMR [4]. Studies on all of these effects so far have primarily made use of the intrinsic anisotropy present in the host (Ga,Mn)As layer. Before they can be harnessed to their full potential, a means of engineering the anisotropy locally is needed, such that multiple elements with different anisotropies can be integrated, and their interactions can be properly investigated.One successful approach to local anisotropy control in metallic ferromagnets has been to make use of shape anisotropy. The same approach has been tried in the prototypical ferromagnetic semiconductor (Ga,Mn)As with lackluster results. In Ref. 5, the authors reported the observation of shape induced anisotropy in (Ga,Mn)As wires of 100 nm thickness x 1.5 x 200 µm 2 , but only over a limited temperature range. Moreover, our own experience in attempting to use wires of similar dimensions have yielded sporadic results with the wires having irreproducible anisotropy, with either biaxial or uniaxial easy axes in inconsistent directions.Furthermore, a simple calculation of the expected shape anisotropy term in such wires indicates that it should not play a significant role. While the infinite rod model used in [5] does predict an appreciable shape anisotropy field given by µ 0 M S /2, where M S is the sample magnetization, it is not applicable to structures which are much thinner than their lateral dimensions. A more exact rectangular prism calculation [6] gives a 5 times weaker shape anisotropy with an anisotropy energy density of 80 J/m 3 which is much too small to compete with the typical crystalline anisotropy of 3000 J/m 3 [5,7] in this material.Growth strain reduces the cubic symmetry of the (Ga,Mn)As zinc-blend crystal structure creating a uniaxial anisotropy with an easy/hard magnetic axis in growth direction when the (Ga,Mn)As layer is tensile/compressively strained.This growth strain is known[8] to influence the strength of the perpendicular component of the anisotropy of the whole layer. Here we discuss (Ga,Mn)As grown on a (001) oriented GaAs substrate, whose out-of-plane hard magnetic axis confines the magnetization in the plane. Phenomenologically, the net in-plane magnetic anisotropy is known to result from a competition of two primary contributions...

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confidence: 63%

Lithographic engineering of anisotropies in (Ga,Mn)As

Hümpfner

Pappert

Wenisch

et al. 2007

Applied Physics Letters

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“…[1][2][3][4][5][6] The aim is to synthesize homogeneous patterns of epitaxial crystals in order to induce quantum confinement-intimately related to the shape and the size of the nanocrystals-in order to achieve enhanced optical and/or magnetic properties. [7][8][9][10][11][12][13] Several theoretical investigations have been concerned with the physical parameters responsible for the geometric properties of the nanocrystals. [14][15][16][17][18][19] The fabrication of such systems can be realized through various techniques involving the formation of nanometerscale islands in a collective way, a process known as selforganization.…”

Section: Introductionmentioning

confidence: 99%

Interface energies of(100)YSZand(111)
Lallet
¹
,
Olivi-Tran
²
,
Lewis
³

2009
Phys. Rev. B
11
1
8
0
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We present an ab initio study of the interface energies of cubic yttria-stabilized zirconia ͑YSZ͒ epitaxial layers on a ͑0001͒ ␣-Al 2 O 3 substrate. The interfaces are modeled using a supercell geometry and the calculations are carried out in the framework of density-functional theory ͑DFT͒ and the local-density approximation ͑LDA͒ using the projector augmented wave ͑PAW͒ pseudopotential approach. Our calculations clearly establish the existence of competing growth mechanisms between ͑111͒ YSZ ʈ ͑0001͒ ␣-Al 2 O 3 and ͑100͒ YSZ ʈ ͑0001͒ ␣-Al 2 O 3 interfaces. This result is central to understanding the behavior of YSZ thin solid film islanding on ͑0001͒ ␣-Al 2 O 3 substrates, either flat or in presence of defects.

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“…Micro-and nano-sized structures of GaMnAs have recently been fabricated and their properties have been the focus of much attention [1][2][3]. Although the magnetization of GaMnAs is commonly characterized by SQUID measurements, measurements using a micromechanical cantilever provide much greater sensitivity than SQUID, as has been demonstrated by the ability to detect single spin [4].…”

Section: Introductionmentioning

confidence: 99%

Mechanically detected field‐induced Mn spin rotation in GaMnAs

Onomitsu

Mahboob

Okamoto

et al. 2008

Phys. Status Solidi (c)

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To study the magnetization properties of a micron‐sized GnMnAs film, we characterize the mechanical properties of a micro‐cantilever integrating a GaMnAs Hall bar. The magnetic field dependence of its mechanical resonance frequency below the Curie temperature is remarkably different from that above the Curie temperature. The frequency shift, which reflects the field‐induced Mn spin rotation, is mainly caused by the magnetoelastic coupling. This result demonstrates that a micromechanical cantilever is a powerful tool for investigating the magnetic properties of micrometer‐sized ferromagnetic materials. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Epitaxial GaMnAs layers and nanostructures with anisotropy in structural and magnetic properties

Cited by 5 publications

References 7 publications

Lithographic engineering of anisotropies in (Ga,Mn)As

Lithographic engineering of anisotropies in (Ga,Mn)As

Interface energies of(100)YSZand(111)
Lallet
¹
,
Olivi-Tran
²
,
Lewis
³

2009
Phys. Rev. B
11
1
8
0
View full text Add to dashboard Cite

Mechanically detected field‐induced Mn spin rotation in GaMnAs

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Epitaxial GaMnAs layers and nanostructures with anisotropy in structural and magnetic properties

Cited by 5 publications

References 7 publications

Lithographic engineering of anisotropies in (Ga,Mn)As

Lithographic engineering of anisotropies in (Ga,Mn)As

Interface energies of(100)YSZand(111)Lallet1, Olivi-Tran2, Lewis3 2009Phys. Rev. B11180View full textAdd to dashboardCite

Mechanically detected field‐induced Mn spin rotation in GaMnAs

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About

Interface energies of(100)YSZand(111)
Lallet
¹
,
Olivi-Tran
²
,
Lewis
³

2009
Phys. Rev. B
11
1
8
0
View full text Add to dashboard Cite