scholarly journals Spin-Glass Transitions in Zn1-xFexO Nanoparticles

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 869 ◽  
Author(s):  
Lilian Felipe S. Tupan ◽  
Marlon I. Valerio-Cuadros ◽  
Aline Alves Oliveira ◽  
Reginaldo Barco ◽  
Flávio Francisco Ivashita ◽  
...  
Keyword(s):  
Spin Glass ◽  
Morphological Changes ◽  
Magnetic Interactions ◽  
Antiferromagnetic Coupling ◽  
Iron Doping ◽  
Drying Process ◽  
Spin Glass Transition ◽  
Spin Polarized ◽  
Doped Zno ◽  
Zno Semiconductor

Monophasic Zn1-xFexO nanoparticles with wurtzite structure were synthesized in the 0 ≤ x ≤ 0.05 concentration range using a freeze-drying process followed by heat treatment. The samples were characterized regarding their optical, structural, and magnetic properties. The analyses revealed that iron doping of the ZnO matrix induces morphological changes in the crystallites. Iron is substitutional for zinc, trivalent and distributed in the wurtzite lattice in two groups: isolated iron atoms and iron atoms with one or more neighboring iron atoms. It was also shown that the energy band gap decreases with a higher doping level. The samples are paramagnetic at room temperature, but they undergo a spin-glass transition when the temperature drops below 75 K. The magnetic frustration is attributed to the competition of magnetic interactions among the iron moments. There are a superexchange interaction and an indirect exchange interaction that is provided by the spin (and charge) itinerant carriers in a spin-polarized band situated in the vicinity of the Fermi level of the Fe-doped ZnO semiconductor. The former interaction actuates for an antiferromagnetic coupling among iron ions, whereas the latter constitutes a driving force for a ferromagnetic coupling that weakens, decreasing the temperature. Our results strongly contribute to the literature because they elucidate the controversies reported in the literature for the magnetic state of the Fe-doped ZnO system.

Magnetic Phase Diagram of Transition Metal Doped ZnO from Density Functional Theory Calculations and Monte Carlo Simulations

2010 ◽  
Vol 1260 ◽  
Author(s):  
Sanjeev K. Nayak ◽  
Heike C. Herper ◽  
Peter Entel
Keyword(s):  
Monte Carlo ◽  
Curie Temperature ◽  
Monte Carlo Simulations ◽  
Ab Initio ◽  
Density Functional ◽  
Magnetic Phase Diagram ◽  
Density Functional Theory Calculations ◽  
Antiferromagnetic Coupling ◽  
Doped Zno ◽  
Co Concentrations

AbstractTransition metals doped ZnO are possible candidates for multiferroics. Here, we have investigated the evolution of ferromagnetism due to Co dopants. The magnetic properties have been studied for Co concentrations from 0 to 100% by using ab-initio methods, i.e., KKR Green's function techniques. In order to estimate the Curie temperature we have performed Monte Carlo simulations with ab-initio calculated exchange parameters.From our calculations the onset of ferromagnetism occurs between 5 to 20% of Co depending on the numerical details of KKR method used. For Co concentrations larger than 50% the system is dominated by antiferromagnetic coupling and no Curie temperature can be obtained.

Spin glass transition and hyperfine parameters in FeO-Al2O3-SiO2glasses

1984 ◽  
Vol 17 (1) ◽  
pp. 127-141 ◽  
Author(s):  
J P Sanchez ◽  
J M Friedt ◽  
R Horne ◽  
A J Van Duyneveldt
Keyword(s):  
Glass Transition ◽  
Spin Glass ◽  
Hyperfine Parameters ◽  
Spin Glass Transition

scholarly journals Investigation of Spin-Glass Transition in Semimagnetic Quantum Wells Based on Cd1-xMnxTe by Means of Optical Spectroscopy

1997 ◽  
Vol 92 (5) ◽  
pp. 1075-1078 ◽  
Author(s):  
U. Zehnder ◽  
D.R. Yakovlev ◽  
W. Ossau ◽  
A. Waag ◽  
G. Landwehr ◽  
...  
Keyword(s):  
Glass Transition ◽  
Quantum Wells ◽  
Spin Glass ◽  
Optical Spectroscopy ◽  
Spin Glass Transition

Electrical Conductivity Measurements of Al-Doped ZnO Semiconductor in High Temperature

2018 ◽  
Vol 772 ◽  
pp. 105-109
Author(s):  
Syamsul Hadi ◽  
Husein Jaya Andika ◽  
Agus Kurniawan ◽  
Suyitno
Keyword(s):  
Electrical Conductivity ◽  
Temperature Effects ◽  
Sintering Temperature ◽  
High Porosity ◽  
Conductivity Measurements ◽  
Grain Sizes ◽  
Lower Porosity ◽  
Doped Zno ◽  
Zno Semiconductor ◽  
Zno Doping

Electrical conductivity plays an important role in the performance of thermoelectric semiconductor material. This study discusses the electrical conductivity measurements of Zinc Oxide (ZnO) doping Aluminium (Al) pellet as a material of thermoelectric using four-point probe method at high temperatures. Al-doped ZnO (2 wt%) pellet was sintered at the temperature of 1100°C, 1200°C, 1300°C, 1400°C, and 1500°C with the heating rate of 8°C/minute. SEM and XRD tests show that the higher sintering temperature effects to larger grain sizes, better crystallinity, and lower porosity. There is no electrical conductivity in the sintering sample at 1100°C due to the small grain sizes and high porosity. In the sintering sample at 1500°C, the phase of ZnAl2O4erupted. The highest electrical conductivity of 5923.48S/m of Al-doped ZnO pellet was obtained at the sintering temperature of 1400°C with measurement temperature of 500°C.

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