Magnetic coupling in Ge nanoparticles

Liou, Y.; Lee, M. S.; You, K. L.

doi:10.1063/1.2773755

Cited by 9 publications

(4 citation statements)

References 19 publications

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“…The ferromagnetic behaviors of the undoped GaAs NWs are quite surprising. Recently, the size-dependent ferromagnetism of Ge nanoparticles (deposited on polystyrene or Si substrates) has been reported . Our research group also observed room-temperature ferromagnetic properties for Ge NWs, and suggested that this originated from the existence of uncompensated spins and surface anisotropy, because of the high surface/volume ratio .…”

Section: Resultsmentioning

confidence: 53%

Room-Temperature Ferromagnetic Ga_1−xMn_xAs (x ≤ 0.05) Nanowires: Dependence of Electronic Structures and Magnetic Properties on Mn Content

Kim¹,

Cho²,

Kong³

et al. 2009

Chem. Mater.

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Ga 1-x Mn x As nanowires were synthesized with finely controlled Mn contents (x ) 0, 0.01, 0.02, 0.03, and 0.05) by the vapor transport method. They consisted of single-crystalline GaAs nanocrystals (avg. diameter ) 60 nm) grown along the [111] direction. The Mn doping decreases the lattice constant, most significantly at x ≈ 0.03. X-ray photoelectron spectroscopy revealed that as the Mn content increases, the binding energy of Ga 2p shifts to a higher energy, which can be correlated with the hybridization between the Mn 2+ ions and the holes. X-ray absorption spectroscopy and X-ray magnetic circular dichroism confirmed that the Mn 2+ ions substitute into the tetrahedrally coordinated Ga sites and that the magnetic moment is maximized at x ) 0.03, where the lattice constant is minimized and the binding energy of Ga 2p is maximized. The magnetization measurement revealed that all of these nanowires exhibited roomtemperature ferromagnetic behavior, which is also observed most significantly for x ≈ 0.03.

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Section: Resultsmentioning

confidence: 53%

Room-Temperature Ferromagnetic Ga_1−xMn_xAs (x ≤ 0.05) Nanowires: Dependence of Electronic Structures and Magnetic Properties on Mn Content

Kim¹,

Cho²,

Kong³

et al. 2009

Chem. Mater.

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“…The ferromagnetic behaviors of undoped Ge NWs are quite surprising. Recently, however, the size-dependent ferromagnetism of Ge nanoparticles (deposited on polystyrene or Si substrates) has been reported . The authors suggested that this was due to the occurrence of the quantum confinement effect owing to their large Bohr radius (∼17 nm).…”

Section: Resultsmentioning

confidence: 99%

Ferromagnetic Ge_1−xM_x (M = Mn, Fe, and Co) Nanowires

Cho¹,

Kim²,

Kim³

et al. 2008

Chem. Mater.

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We synthesized Ge and Ge 1-x M x (M ) Mn, Co, and Fe, x e 0.4) nanowires using the thermal vapor transport method. All of the nanowires consisted of single-crystalline Ge nanocrystals grown uniformly with the [111] direction. High-resolution X-ray diffraction showed no metal cluster formation for any of the Ge 1-x M x nanowires, and the reduction of the lattice constant for the Mn-substituted nanowires. X-ray absorption spectroscopy and X-ray magnetic circular dichroism measurements revealed that the Mn 2+ ions preferentially occupy the tetrahedral sites, substituting for Ge. The magnetic moment of the Mn ions reaches a maximum for x ) 0.1, which is much larger than that of the Fe or Co ions. The magnetic hysteresis confirms the room-temperature ferromagnetism of the Ge 1-x Mn x nanowires, which is also maximized at x ) 0.1. We suggest that the Mn ions produce dopant-acceptor hybridization with host defects in the p-type Ge nanowires. The Mn substitution is more effective to form significant ferromagnetic Ge nanowires, compared to the Fe or Co substitution.

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“…While high-temperature ferromagnetism has never been confirmed in GeMn films with properly diluted magnetic defects, unusual magnetic properties of Ge 1−x Mn x quasi-onedimensional ͑1D͒ nanostructures [11][12][13][14][15][16] and even intrinsic ferromagnetism in magnetically undoped Ge quantum dots 17,18 have been demonstrated recently. Perfect dilution of Mn ions in the host accompanied by a high Curie temperature, correlation between electrical and magnetic properties, existence of charge and spin carriers in a magnetically ordered lattice, [19][20][21] and other remarkable features of these systems make them attractive for spintronic applications.…”

Section: Introductionmentioning

confidence: 98%

Effect of magnetic defects and dimensionality on the spin dynamics of GeMn systems: Electron spin resonance measurements

et al. 2008

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Effects of dimensionality on magnetic and electric properties of one-and two-dimensional GeMn systems and the role of defects in magnetic ordering are investigated by means of electron spin resonance ͑ESR͒ and superconducting quantum interference device magnetometry techniques. Arrays of Ge 1−x Mn x nanowires and thin Ge:Mn films with similar concentrations of the magnetic impurity ͑x =1% -8%͒ have been fabricated by chemical synthesis and ion implantation, respectively. In magnetically homogeneous Ge 1−x Mn x nanowires, all observed electron spin resonances are related to absorption on individual magnetic centers ͑Mn 3+ and Mn 2+ ions and polarized charge carriers͒ in a broad temperature range, T = 5 -300 K. On the other hand, in strongly inhomogeneous 2D GeMn films, a collective spin excitation, the spin-wave resonance, is observed at low temperatures, T =5-60 K. This signifies the presence of long-range spin states and a cooperative magnetic response originating from crystalline Mn 5 Ge 3 precipitates and Mn-rich amorphous nanoclusters as well as diluted Mn ions. Additionally, a strong negative background was observed and attributed to the microwave magnetoresistance of the Ge:Mn thin films. The absence of the magnetoresistance in Ge 1−x Mn x nanowires indicates that the scattering of charge carriers is determined by dimensions of the structure. Overall, our analysis of magnetic-resonance phenomena reveals a significant difference between one-dimensional and twodimensional magnetic semiconductors. It emphasizes the important role of dimensionality as well as the type and distribution of magnetic defects in spin-dependent scattering and dynamic magnetic properties of GeMn semiconductors.

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Magnetic coupling in Ge nanoparticles

Cited by 9 publications

References 19 publications

Room-Temperature Ferromagnetic Ga_1−xMn_xAs (x ≤ 0.05) Nanowires: Dependence of Electronic Structures and Magnetic Properties on Mn Content

Room-Temperature Ferromagnetic Ga_1−xMn_xAs (x ≤ 0.05) Nanowires: Dependence of Electronic Structures and Magnetic Properties on Mn Content

Ferromagnetic Ge_1−xM_x (M = Mn, Fe, and Co) Nanowires

Effect of magnetic defects and dimensionality on the spin dynamics of GeMn systems: Electron spin resonance measurements

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Magnetic coupling in Ge nanoparticles

Cited by 9 publications

References 19 publications

Room-Temperature Ferromagnetic Ga1−xMnxAs (x ≤ 0.05) Nanowires: Dependence of Electronic Structures and Magnetic Properties on Mn Content

Room-Temperature Ferromagnetic Ga1−xMnxAs (x ≤ 0.05) Nanowires: Dependence of Electronic Structures and Magnetic Properties on Mn Content

Ferromagnetic Ge1−xMx (M = Mn, Fe, and Co) Nanowires

Effect of magnetic defects and dimensionality on the spin dynamics of GeMn systems: Electron spin resonance measurements

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Product

Resources

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Room-Temperature Ferromagnetic Ga_1−xMn_xAs (x ≤ 0.05) Nanowires: Dependence of Electronic Structures and Magnetic Properties on Mn Content

Room-Temperature Ferromagnetic Ga_1−xMn_xAs (x ≤ 0.05) Nanowires: Dependence of Electronic Structures and Magnetic Properties on Mn Content

Ferromagnetic Ge_1−xM_x (M = Mn, Fe, and Co) Nanowires