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

Xiang, Gang; Holleitner, Alexander W.; Sheu, B. L.; Mendoza, F. M.; Maksimov, O.; Stone, M. B.; Schiffer, P.; Awschalom, D. D.; Samarth, N.

doi:10.1103/physrevb.71.241307

Cited by 44 publications

(34 citation statements)

References 19 publications

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“…1,2,3,4,5,6,7,8 Such films possess several magnetic phases in which the magnetization can be uniformly normal to the plane, canted, or periodically modulated in one direction (striped). Magnetization curves exhibit intricate magnetic hysteresis indicating coexistence of phases.…”

Section: Introductionmentioning

confidence: 99%

Stripes in thin ferromagnetic films with out-of-plane anisotropy

2007

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We examine the T = 0 phase diagram of a thin ferromagnetic film with a strong out-of-plane anisotropy (e.g. Co/Pt multilayers) in the vicinity of the reorientation phase transition. The phase diagram in the anisotropy-applied field plane is universal in the limit in which the film thickness is the shortest length scale. It contains uniform fully magnetized and canted phases, as well as periodically nonuniform states: weakly modulated spin-density waves and strongly modulated stripes. We determine the boundaries of metastability of these phases and point out the existence of a critical point at which the difference between the SDW and striped phases vanishes. Out-of-plane magnetization curves exhibit hysteresis loops caused by the coexistence of one or more phases. Additionally, we study the effect of a system edge on the orientation of nearby stripes. We compare our results with recent experiments.

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Section: Introductionmentioning

confidence: 99%

Stripes in thin ferromagnetic films with out-of-plane anisotropy

2007

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“…In earlier studies, control of the magnetic anisotropy has been achieved by modifying the strain in the layer. Tensile strain can be imposed on the (Ga,Mn)As by growing it on a thick, plastically relaxed (In,Ga)As buffer with a larger lattice parameter, and results in an out-of-plane easy axis [3,4].Here, we follow an alternative approach in modifying the lattice strain of (Ga,Mn)As on GaAs by lithography, which allows us to locally control the magnetic anisotropy of the material. By structuring a fully pseudomorphic 70 nm (Ga,Mn)As layer into thin, elongated stripes, we allow anisotropic, elastic strain relaxation perpendicular to the long axis of the stripe.…”

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confidence: 99%

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confidence: 99%

Control of Magnetic Anisotropy in(Ga,Mn)Asby Lithography-Induced Strain Relaxation

et al. 2007

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We obtain control of magnetic anisotropy in epitaxial (Ga,Mn)As by anisotropic strain relaxation in patterned structures. The strain in the structures is characterized using sophisticated X-ray techniques. The magnetic anisotropy before patterning of the layer, which shows biaxial easy axes along [100] and [010], is replaced by a hard axis in the direction of large elastic strain relaxation and a uniaxial easy axis in the direction where pseudomorphic conditions are retained. This strong anisotropy can not be explained by shape anisotropy and is attributed solely to lattice strain relaxation. Upon increasing the uniaxial strain anisotropy in the (Ga,Mn)As stripes, we also observe an increase in magnetic anisotropy.PACS numbers: 75.50. Pp, 75.30.Gw The (Ga,Mn)As material system has been the focus of many studies over the last years. As the understanding of its complex transport and magnetic properties increases, the focus of interest shifts from basic research towards its application in devices. For this, it is necessary to understand how different parameters influence the ferromagnetic material in structures at the device level. In this letter we present a systematic study of the role of strain relaxation as the dominating factor contributing to the magnetic anisotropy in (Ga,Mn)As nanostructures. A (Ga,Mn)As layer grown epitaxially on a GaAs substrate is subject to compressive strain in the plane of the sample and typically exhibits biaxial in-plane easy axes along [100] and [010], at temperatures around 4 K [1, 2]. In earlier studies, control of the magnetic anisotropy has been achieved by modifying the strain in the layer. Tensile strain can be imposed on the (Ga,Mn)As by growing it on a thick, plastically relaxed (In,Ga)As buffer with a larger lattice parameter, and results in an out-of-plane easy axis [3,4].Here, we follow an alternative approach in modifying the lattice strain of (Ga,Mn)As on GaAs by lithography, which allows us to locally control the magnetic anisotropy of the material. By structuring a fully pseudomorphic 70 nm (Ga,Mn)As layer into thin, elongated stripes, we allow anisotropic, elastic strain relaxation perpendicular to the long axis of the stripe. To increase the strain in the structure compared to the case of (Ga,Mn)As on GaAs, a second sample is processed which includes a highly compressively strained layer acting as an extra stressor to the overlying (Ga,Mn)As layer. The uniaxial strain relaxation in the structures is investigated by grazing incidence X-ray diffraction (GIXRD) and high-resolution X-ray diffraction (HRXRD). To determine the influence of patterning on the magnetic anisotropy, a series of magnetometric and magnetotransport studies are performed. We also present finite-element simulations of anisotropic strain relaxation and k ·p calculations which confirm the relationship between the structural and magnetic behavior observed in our samples.The samples are grown in a dedicated III-V MBE chamber with effusion cells for Ga, In, Mn, and a valved As 4 cell. A 200 nm thic...

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“…[23] The former results in a strong out-of-plane easy axis, and has been investigated in detail. [24,25] …”

Section: General Anisotropy Propertiesmentioning

confidence: 98%

Magnetic Anisotropies and (Ga,Mn)As‐based Spintronic Devices

et al. 2007

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In this Review, we discuss the rich anisotropic properties of the ferromagnetic semiconductor (Ga,Mn)As, and their implications in transport studies. We review the various sources and types of anisotropy seen in the material, discuss its magnetization reversal process, and demonstrate how basic transport properties, such as resistivity and Hall measurements, can be used as very sensitive tools to investigate the magnetization properties of the material. We also discuss how the magnetic anisotropy, coupled with large spin–orbit coupling, leads to an anisotropy in the transport density of states, which in turn leads to fundamentally novel behavior such as tunneling anisotropic magnetoresistance (TAMR).

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

Cited by 44 publications

References 19 publications

Stripes in thin ferromagnetic films with out-of-plane anisotropy

Stripes in thin ferromagnetic films with out-of-plane anisotropy

Control of Magnetic Anisotropy in(Ga,Mn)Asby Lithography-Induced Strain Relaxation

Magnetic Anisotropies and (Ga,Mn)As‐based Spintronic Devices

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