Properties of Ferromagnetic GaGdN

2006 ◽  
Vol 955 ◽  
Author(s):  
J. K. Hite ◽  
R. P. Davies ◽  
R. M. Frazier ◽  
G. T. Thaler ◽  
C. R. Abernathy ◽  
...  
Keyword(s):  
Room Temperature ◽  
Single Phase ◽  
Room Temperature Ferromagnetism ◽  
Magnetic Ordering ◽  
Structural Defects ◽  
Drastic Reduction ◽  
Sapphire Substrates ◽  
Undoped Material ◽  
Si Content ◽  
Curie Temperatures

ABSTRACTSingle phase GaGdN and GaGdN:Si films were grown on sapphire substrates. The undoped films were highly resistive films but became conductive with the addition of Si. SQUID magnetometry indicated room temperature ferromagnetism in both types of materials. Structural defects had a strong influence on the magnetic ordering of the material, as seen in a drastic reduction of magnetic moment with degrading crystalline quality. Magnetization of the co-doped film increased with Si content, reaching levels higher than that of the undoped material. Gd-doped AlN films grown in a similar fashion also displayed Curie temperatures above room temperature.

scholarly journals Photoluminescence studies on structural defects and room temperature ferromagnetism in Ni and Ni–H doped ZnO nanoparticles

2010 ◽  
Vol 108 (2) ◽  
pp. 023906 ◽  
Author(s):  
Liu-Niu Tong ◽  
Teng Cheng ◽  
Huai-Bin Han ◽  
Jin-Lian Hu ◽  
Xian-Mei He ◽  
...  
Keyword(s):  
Zno Nanoparticles ◽  
Room Temperature ◽  
Room Temperature Ferromagnetism ◽  
Structural Defects ◽  
Doped Zno ◽  
Photoluminescence Studies

Room-Temperature Ferromagnetism in Co-Doped SrTiO3 Nanofibres

2012 ◽  
Vol 512-515 ◽  
pp. 1438-1441
Author(s):  
Wei Zhang ◽  
He Ping Li ◽  
Wei Pan
Keyword(s):  
Room Temperature ◽  
Oxygen Vacancies ◽  
Room Temperature Ferromagnetism ◽  
Sol Gel ◽  
Magnetic Ordering ◽  
Second Phase ◽  
Co Doped

In this article, Co-doped SrTiO3 nanofibres have been prepared by electrospinning from a sol-gel precursor and the following calcination at 923K. XRD results confirmed that no second phase was formed, and Co ions successfully occupied the Ti sites. By annealing in hydrogen, oxygen vacancies and (Co-H-Co) were formed, which both contributed to the magnetic ordering in SrTi1-xCoxO3 nanofibres are at 300K.

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.

scholarly journals Electronic phase-crossover and room temperature ferromagnetism in a two-dimensional (2D) spin lattice

RSC Advances ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 946-952
Author(s):  
A. K. Nair ◽  
S. J. Ray
Keyword(s):  
High Temperature ◽  
Curie Temperature ◽  
Room Temperature ◽  
Room Temperature Ferromagnetism ◽  
Magnetic Ordering ◽  
Metallic State ◽  
Two Dimensional ◽  
Half Metallic ◽  
Spin Lattice ◽  
Electronic Phase

In the presence of strain, high temperature magnetic ordering in Cr2Ge2Te6 was observed with electronic phase crossover from semiconducting to half-metallic state. On coupling strain and electric field, the Curie temperature reaches 331 K.

Excitons bound to structural defects in GaN

2001 ◽  
Vol 693 ◽  
Author(s):  
M. A. Reshchikov ◽  
D. Huang ◽  
F. Yun ◽  
H. Morkoç ◽  
R. J. Molnar ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Room Temperature ◽  
Molecular Beam ◽  
Structural Defects ◽  
Excitation Density ◽  
High Quality ◽  
Pl Spectra ◽  
Sapphire Substrates ◽  
Uv Illumination ◽  
Increasing Temperature

AbstractWe analyzed the photoluminescence (PL) spectra of undoped GaN films grown by molecular beam epitaxy on sapphire substrates. While the PL spectra from high-quality samples contain free and bound exciton peaks only, the spectra from some samples involve sharp unidentified peaks in the energy range of 3.0 – 3.45 eV, specifically at 3.21, 3.32, 3.36, and 3.42 eV. We attribute these peaks to excitons bound to defects because of the linear and sometimes superlinear increase in their intensity with excitation density without saturation up to 100 W/cm2. With increasing temperature these peaks quench in a well-known fashion similar to that for excitons. In order to relate the observed peaks to the structural defects, we etched selected samples in hot H3PO4 acid or, alternatively, with photo-electrochemical (PEC) etching at room temperature in the presence of UV-illumination in a dilute KOH solution. In the former case the dislocations were etched leaving etched pits on the surface, while in the latter case the dislocations remained unetched due to a deficit of photogenerated holes at dislocation sites. We found that the 3.42 eV peak disappeared after both hot wet and PEC etching suggesting that the associated defect is at the GaN surface. Peaks at 3.21 and 3.36 eV could be enhanced greatly by PEC etching, which were correlated to bulk dislocations.

Structural defects-mediated room-temperature ferromagnetism in Co-doped SnO2 insulating films

2009 ◽  
Vol 517 (21) ◽  
pp. 6091-6095 ◽  
Author(s):  
X.F. Liu ◽  
W.M. Gong ◽  
Javed Iqbal ◽  
B. He ◽  
R.H. Yu
Keyword(s):  
Room Temperature ◽  
Room Temperature Ferromagnetism ◽  
Structural Defects ◽  
Insulating Films ◽  
Co Doped

scholarly journals Increased room temperature ferromagnetism in Co-doped tetrahedral perovskite niobates

2021 ◽  
Vol 8 (10) ◽  
Author(s):  
Yi Zhou ◽  
Qing He ◽  
Fei Zhou ◽  
Xingqi Liao ◽  
Yong Liu ◽  
...  
Keyword(s):  
Room Temperature ◽  
Magnetic Semiconductors ◽  
Room Temperature Ferromagnetism ◽  
Dilute Magnetic Semiconductors ◽  
Defect Band ◽  
Co Doping ◽  
Band Absorption ◽  
Local Spin Polarization ◽  
Curie Temperatures ◽  
Co Doped

Dilute magnetic semiconductors (DMSs), such as (In, Mn)As and (Ga, Mn)As prototypes, are limited to III–V semiconductors with Curie temperatures ( T c ) far from room temperature, thereby hindering their wide application. Here, one kind of DMS based on perovskite niobates is reported. BaM x Nb (1− x ) O 3− δ ( M = Fe, Co) powders are prepared by the composite-hydroxide-mediated method. The addition of M elements endows BaM x Nb (1− x ) O 3− δ with local ferromagnetism. The tetragonal BaCo x Nb (1− x ) O 3− δ nanocrystals can be obtained by Co doping, which shows strong saturation magnetization ( M sat ) of 2.22 emu g −1 , a remnant magnetization ( M r ) of 0.084 emu g −1 and a small coercive field ( H c ) of 167.02 Oe at room temperature. The ab initio calculations indicate that Co doping could lead to a 64% local spin polarization at the Fermi level ( E F ) with net spin DOS of 0.89 electrons eV −1 , this result shows the possibility of maintaining strong ferromagnetism at room temperature. In addition, the trade-off effect between the defect band absorption and ferromagnetic properties of BaM x Nb (1− x ) O 3− δ is verified experimentally and theoretically.

Intrinsic Ferromagnetism of the GaMnN Thin Films

2012 ◽  
Vol 629 ◽  
pp. 49-54
Author(s):  
Xing Guo Gao ◽  
Bao Yuan Man ◽  
Mei Liu ◽  
Cheng Yang ◽  
Chuan Song Chen ◽  
...  
Keyword(s):  
Room Temperature ◽  
Room Temperature Ferromagnetism ◽  
Double Exchange ◽  
Nitrogen Pressure ◽  
Photoelectron Spectra ◽  
Ferromagnetic Behavior ◽  
Sapphire Substrates ◽  
Intrinsic Ferromagnetism ◽  
Mn Doped

The Mn-doped GaN (GaMnN) films on c-plane sapphire substrates were prepared by using Laser Molecular Beam Epitaxy (LMBE) at different base nitrogen pressure, followed by annealing in the ammonia atmosphere at 950 °C for 30 min, to study the original reason of the room-temperature ferromagnetism of GaMnN films. We found the crystalline quality was sensitive to the base nitrogen pressure during growth. X-ray photoelectron spectra (XPS) analysis confirmed that the Mn3+ and Mn2+ coexist in our samples. The room-temperature ferromagnetic behavior can be explained by double exchange. The ferromagnetism would be weakened by the nitrogen vacancies, which plays a role of donor.

Sign in / Sign up

Export Citation Format

Share Document