The Dependence of the Magnetic Properties of GaMnN on Codoping by Mg and Si

2004 ◽  
Vol 834 ◽  
Author(s):  
Mason J. Reed ◽  
M. Oliver Luen ◽  
Meredith L. Reed ◽  
Salah M. Bedair ◽  
Fevzi Erdem Arkun ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Fermi Level ◽  
Energy Band ◽  
Room Temperature ◽  
Dopant Concentration ◽  
Room Temperature Ferromagnetism ◽  
Chemical Vapor ◽  
Material System ◽  
Si Doped ◽  
Mg Doped

ABSTRACTThe magnetic properties of GaMnN, grown by metalorganic chemical vapor deposition, depend on the addition of dopants; where undoped materials are ferromagnetic, and n -type (Si-doped) and p -type (Mg-doped) films are either ferromagnetic or paramagnetic depending on dopant concentration. The ferromagnetism of this material system seems correlated to Fermi level position, and is observed only when the Fermi level is within or close to the Mn energy band. This allows ferromagnetism-mediating carriers to be present in the Mn energy band. The current results exclude precipitates or clusters as the origin of room temperature ferromagnetism in GaMnN.

Evidence of Carrier Mediated Ferromagnetism in GaN:Mn/GaN:Mg Heterostructures

2004 ◽  
Vol 831 ◽  
Author(s):  
F. Erdem Arkun ◽  
Mason J. Reed ◽  
Erkan Acar Berkman ◽  
Nadia A. El-Masry ◽  
John M. Zavada ◽  
...  
Keyword(s):  
Fermi Level ◽  
Room Temperature ◽  
Theoretical Calculations ◽  
Room Temperature Ferromagnetism ◽  
Dilute Magnetic Semiconductors ◽  
Organic Chemical ◽  
Material System ◽  
Secondary Phases ◽  
Fermi Level Position ◽  
Carrier Transfer

ABSTRACTDilute Magnetic Semiconductors (DMS's) posses a strong potential to make use of the spin of carriers in spintronic devices. Experimental results and theoretical calculations predict that GaN:Mn is a potential semiconductor material for spintronic device applications. The dependence of the room temperature ferromagnetic properties of GaN:Mn/GaN:Mg double heterostructures (DHS) on the Fermi level position in the crystal is demonstrated. Several GaN:Mn/GaN:Mg DHS are grown by metal organic chemical vapor deposition on sapphire. It is shown that initially paramagnetic films can be rendered ferromagnetic by facilitating carrier transfer through the GaN:Mn/GaN:Mg interface. Additionally, it is demonstrated that ferromagnetism depends on the thickness of the GaN:Mn and GaN:Mg layers. The carrier transfer process essentially changes the Fermi level position in the crystal. By choosing the right thicknesses for GaN:Mn and GaN:Mg an optimum DHS that exhibits room temperature ferromagnetism is grown. An identical structure, with the exception of insertion of an AlGaN barrier in order to obstruct the carrier transfer at the interface, results in paramagnetic films for AlGaN barriers thicker than 25nm. These results are explained based on the change in the occupancy of the 3d-Mn impurity band, and indicate that carrier mediation is the possible mechanism for the ferromagnetism observed in the MOCVD grown GaN:Mn material system. This is the first evidence that this material system responds to electronic perturbations, hence ferromagnetism observed is not due to secondary phases or spin glass behavior.

Comparison of the Incorporation of Various Transition Metals into GaN by MOCVD

2006 ◽  
Vol 955 ◽  
Author(s):  
Matthew H Kane ◽  
William Fenwick ◽  
Nola Li ◽  
Shalini Gupta ◽  
Eun Hyun Park ◽  
...  
Keyword(s):  
Transition Metals ◽  
Room Temperature ◽  
Room Temperature Ferromagnetism ◽  
Magnetic Hysteresis ◽  
Chemical Vapor ◽  
Magnetic Ordering ◽  
Growth Conditions ◽  
Shallow Donor ◽  
Organic Chemical ◽  
Secondary Phases

ABSTRACTThe incorporation of transition metals in GaN has long been of interest in spintronics due to theoretical predictions of room temperature ferromagnetism in these materials. However, the mechanism of the observed ferromagnetism of the nitride-based DMS is still controversial, and may originate from a carrier-mediated, defect-related or nanoscale clustering mechanism. In this work, we present a comparative study of the incorporation of various transition metals and their effect on the optical, structural, and magnetic properties of GaN. Metal-organic chemical vapor deposition (MOCVD) has been employed to produce epitaxial films of varying thickness and manganese and iron doping using bis-cyclopentyldienyl(magnanese,iron) as the transition metal sources. High-resolution X-ray diffraction reveals no secondary phases under optimized growth conditions. Magnetic hysteresis is observed at room temperature in both GaMnN and GaFeN, though the strength of the magnetic ordering is roughly an order of magnitude weaker in the Fe-alloyed samples. Increasing Mn concentrations significantly affect long-range lattice ordering, and the observation of local vibrational modes (LVMs) supports the formation of nitrogen vacancies, even under optimized MOCVD growth conditions. Such vacancies form shallow donor complexes and thus contribute to self-compensation. A disorder-induced mode at 300 cm−1 and a LVM due to vacancies at 669 cm-1 were revealed by Raman spectroscopy.

Room Temperature Ferromagnetism and Band Gap Engineering in Mg Doped ZnO RF/DC Sputtered Films

2013 ◽  
Vol 1577 ◽  
Author(s):  
Sreekanth K. Mahadeva ◽  
Zhi-Yong Quan ◽  
Jin-Cheng Fan ◽  
Hasan B. Albargi ◽  
Gillian A Gehring ◽  
...  
Keyword(s):  
Band Gap ◽  
Room Temperature ◽  
Room Temperature Ferromagnetism ◽  
Ambient Conditions ◽  
Zno Film ◽  
Band Gap Engineering ◽  
Sputtered Films ◽  
Doped Zno ◽  
Mg Doped ◽  
Comprehensive Study

ABSTRACTMg doped ZnO thin films were prepared by DC/RF magnetron co-sputtering in (Ar+O2) ambient conditions using metallic Mg and Zn targets. We present a comprehensive study of the effects of film thickness on the structural, optical and magnetic properties. Room temperature ferromagnetism was observed in the films and the saturation magnetization (MS) increases at first as the film’s thickness increases and then decreases. The MS value as high as ∼15.76 emu/cm3 was achieved for the Mg-doped ZnO film of thickness 120 nm. The optical band gap of the films determined to be in the range 3.42 to 3.52 eV.

Synthesis and room-temperature ferromagnetism of cobalt-doped SnO2 nanowires

2009 ◽  
Vol 24 (6) ◽  
pp. 2001-2005 ◽  
Author(s):  
Jin Wu ◽  
Ke Yu ◽  
Yongsheng Zhang ◽  
Lijun Li ◽  
Ziqiang Zhu
Keyword(s):  
Room Temperature ◽  
Room Temperature Ferromagnetism ◽  
Chemical Vapor ◽  
Average Diameter ◽  
Magnetization Measurement ◽  
Chemical Vapor Transport ◽  
Ferromagnetic Properties ◽  
Transmission Electron ◽  
Sno2 Nanowires ◽  
Ferromagnetic Hysteresis

We have observed ferromagnetism in dilute cobalt-doped SnO2 nanowires at room temperatures. The Co-doped SnO2 nanowires with an average diameter of ∼50 nm were synthesized by the thermal chemical vapor transport method. High-resolution transmission electron microscopy and energy-dispersive x-ray spectroscopy analyses demonstrate that the nanowires are single-crystal structures and Co is homogeneously doped into the SnO2 lattice. The ferromagnetic hysteresis curves and temperature-dependent magnetization measurement provide evidence for ferromagnetic properties with a Curie temperature above room temperature. Oxygen annealing has been performed to study the roles played by the oxygen vacancies in determining the ferromagnetic properties of the nanowires.

scholarly journals Structure and Ferromagnetism in Carbon Nanofibers from PAN/PVP

2021 ◽  
Author(s):  
Suminya - Teeta ◽  
Somchai - Sonsupap ◽  
Ratchaneekorn - Wanchanthuek ◽  
Santi - Maensiri ◽  
Narong - Chanlek ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Carbon Nanofibers ◽  
Chemical Bonding ◽  
Photoelectron Spectroscopy ◽  
Room Temperature ◽  
New Technologies ◽  
Room Temperature Ferromagnetism ◽  
Weight Ratio ◽  
Average Diameter ◽  
X Ray

Abstract We report on the room-temperature ferromagnetism in carbon nanofibers. Carbon nanofibers were fabricated using sequential electrospinning of polyacrylonitrile (PAN) and polyvinylpyrrolidone (PVP). The morphologies, crystal structures, chemical bonding states and magnetic properties were characterized for three different polyacrylonitrile (PAN) to polyvinylpyrrolidone (PVP) weight ratios (10:0, 7:3 and 6:4) of PAN/PVP. The as-spun PAN/PVP were carbonized in three steps; stabilization, carbonization and activation at 800 ºC to obtain carbon nanofibers. The morphology and structure of the carbon nanofibers (CNFs) were completely characterized by field emission scanning electron microscopy (FE-SEM), x-ray diffraction (XRD) and Raman spectroscopy. The elemental composition and the chemical bonding of CNFs were analyzed by x-ray photoelectron spectroscopy (XPS), the magnetic properties of CNFs were measured by vibrating sample magnetometer (VSM) at room-temperature. XRD patterns showed the phase of amorphous carbon structure. The average diameter sizes of the carbon nanofibers ranged from 340 to 484 nm. Raman analysis was used to determine the carbon qualities in the samples by the numbers of sp3/sp2 hybridized atoms. Chemical analysis with XPS indicated that there were no magnetic contaminants in the samples. The PAN/PVP weight ratio of 6:4 showed ferromagnetic carbon nanofibers with the highest specific magnetization as ~144.2 memu/g at 300 K. These results inspire us to further research the potential of carbon materials, as a completely new class of magnetic devices. This will aid the development of new technologies in the near future.

scholarly journals Influence of Ag nanoparticles on the physical properties of multilayers of graphene

DYNA ◽  
2019 ◽  
Vol 86 (211) ◽  
pp. 49-53
Author(s):  
Jose Edgar Alfonso ◽  
John Jairo Olaya
Keyword(s):  
Magnetic Properties ◽  
Seebeck Coefficient ◽  
Physical Properties ◽  
Vapor Deposition ◽  
Ag Nanoparticles ◽  
Room Temperature ◽  
Deposition Time ◽  
Chemical Vapor ◽  
Initial Value ◽  
Cvd Method

Graphene has attracted considerable interest due its exceptional physical properties. This article describes the thermoelectric and magnetic properties such as the Seebeck coefficient and the magnetoresistance, at room temperature, of multilayers of graphene fabricated through the chemical vapor deposition (CVD) method and coated with Ag nanoparticles (NPs). According to the results, the Seebeck coefficient increased from -30 to -5 μV/K as a function of deposition time of Ag NPsand magnetoresistance increase their initial value as a function of sheet resistance up to 16.6%.

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