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1.
In this review article,we review the progress made in the past several years mainly regarding the efforts devoted to increasing the Curie temperature(T C) of(Ga,Mn)As,which is most widely considered as the prototype ferromagnetic semiconductor.Heavy Mn doping,nanostructure engineering and post-growth annealing which increase T C are described in detail.  相似文献   

2.
刘兴翀  陆智海  张凤鸣 《中国物理 B》2010,19(2):27502-027502
This paper reports that Zn0.97Mn0.03O thin films have been prepared by radio-frequency sputtering technology followed by rapid thermal processing in nitrogen and oxygen ambient respectively. Magnetic property investigation indicates that the films are ferromagnetic and that the Curie temperature (Tc) is over room temperature. It is observed that the saturation magnetization of the films increases after annealing in nitrogen ambience but decreases after annealing in oxygen. Room temperature photoluminescence spectra indicate that the amount of defects in the films differs after annealing in the different ambiences. This suggests that the ferromagnetism in Zn0.97Mn0.03O films is strongly related to the defects in the films.  相似文献   

3.
黄征  武莉莉  黎兵  郝霞  贺剑雄  冯良桓  李卫  张静全  蔡亚平 《中国物理 B》2010,19(12):127204-127204
In order to fabricate AlSb polycrystalline thin films without post annealing,this paper studies a technology of magnetron co-sputtering onto intentionally heated substrate.It compares the structural characteristics and electrical properties of AlSb films which are deposited at different substrate temperatures.It finds that the films prepared at a substrate temperature of 450 C exhibit an enhanced grain growth with an average grain size of 21 nm and the lattice constant is 0.61562 nm that goes well with unstained lattice constant(0.61355 nm).The ln(σ dark) ~ 1/T curves show that the conductivity activation energy is about 0.38 eV when the film is deposited at 450 C without an annealing.The transmittance and reflectance spectra show that the film deposited at 450 C has an optical band gap of 1.6 eV.These results indicate that we have prepared AlSb polycrystalline films which do not need a post annealing.  相似文献   

4.
李炎勇  汪华锋  曹玉飞  王开友 《中国物理 B》2013,22(2):27504-027504
We investigated the effect of low temperature annealing on magnetic anisotropy in 7-nm ultrathin Ga0.94Mn0.06As devices by measuring the angle-dependent planar Hall resistance(PHR).Obvious hysteresis loops were observed during the magnetization reversal through the clockwise and counterclockwise rotations under low magnetic fields(below 1000 Gs,1 Gs = 10-4 T),which can be explained by competition between Zeeman energy and magnetic anisotropic energy.It is found that the uniaxial anisotropy is dominant in the whole measured ferromagnetic range for both the as-grown ultrathin Ga0.94Mn0.06As and the annealed one.The cubic anisotropy changes more than the uniaxial anisotropy in the measured temperature ranges after annealing.This gives a useful way to tune the magnetic anisotropy of ultrathin(Ga,Mn)As devices.  相似文献   

5.
刘贵斌  刘邦贵 《中国物理 B》2009,18(11):5047-5054
We study (Ga,Mn)As diluted magnetic semiconductors in terms of the Ruderman–Kittel–Kasuya–Yosida quantum spin model in Green’s function approach.Random distributions of the magnetic atoms are treated by using an analytical average of magnetic configurations.Average magnetic moments and spin excitation spectra as functions of temperature can be obtained by solving self-consistent equations,and the Curie temperature TC is given explicitly.TC is proportional to magnetic atomic concentration,and there exists a maximum for TC as a function of carrier concentration.Applied to (Ga,Mn)As,the theoretical results are consistent with experiment and the experimental TC can be obtained with reasonable parameters.This modelling can also be applied to other diluted magnetic semiconductors.  相似文献   

6.
<正>Black-coloured GaN nanoparticles with an average grain size of 50 nm have been obtained by annealing GaN nanoparticles under flowing nitrogen at 1200℃for 30 min.XRD measurement result indicates an increase in the lattice parameter of the GaN nanoparticles annealed at 1200℃,and HRTEM image shows that the increase cannot be ascribed to other ions in the interstitial positions.If the as-synthesised GaN nanoparticles at 950℃are regarded as standard,the thermal expansion changes nonlinearly with temperature and is anisotropic;the expansion below 1000℃is smaller than that above 1000℃.This study provides an experimental demonstration for selecting the proper annealing temperature of GaN.In addition,a large blueshift in optical bandgap of the annealed GaN nanoparticles at 1200℃is observed,which can be ascribed to the dominant transitions from the C(Γ7) with the peak energy at 3.532 eV.  相似文献   

7.
肖洪地  毛宏志  林兆军  马洪磊 《中国物理 B》2010,19(8):86106-086106
<正>Black-coloured GaN nanoparticles with an average grain size of 50 nm have been obtained by annealing GaN nanoparticles under flowing nitrogen at 1200℃for 30 min.XRD measurement result indicates an increase in the lattice parameter of the GaN nanoparticles annealed at 1200℃,and HRTEM image shows that the increase cannot be ascribed to other ions in the interstitial positions.If the as-synthesised GaN nanoparticles at 950℃are regarded as standard,the thermal expansion changes nonlinearly with temperature and is anisotropic;the expansion below 1000℃is smaller than that above 1000℃.This study provides an experimental demonstration for selecting the proper annealing temperature of GaN.In addition,a large blueshift in optical bandgap of the annealed GaN nanoparticles at 1200℃is observed,which can be ascribed to the dominant transitions from the C(Γ_7) with the peak energy at 3.532 eV.  相似文献   

8.
The temperature dependence of lattice constants a and c of intermetallic compounds RMn2Ge2 (R=Sm, Gd) is measured in the temperature range 10-800K by using the x-ray diffraction method. The magnetoelastic anomalies of lattice constants are found at the different kinds of spontaneous magnetic transitions. The transversal and longitudinal magnetostrictions of polycrystalline samples are measured in the pulse magnetic field up to 25T. In the external magnetic field there occurs a first-order field-induced antiferromagnetism-ferromagnetism transition in the Mn sublattice, which gives rise to a large magnetostriction. The magnitude of magnetostrictions is as large as 10-3. The transversal and longitudinal magnetostrictions have the same sign and are almost equal. This indicates that the magnetostriction is isotropic and mainly caused by the interlayer Mn-Mn exchange interaction. The experimental results are explained in the framework of a two-sublattice ferrimagnet with the negative exchange interaction in one of the sublattices by taking into account the lattice constant dependence of interlayer Mn-Mn exchange interaction.  相似文献   

9.
ErGa_(3-x)Mn_x disordered alloy is successfully prepared by the vacuum arc melting technology, and the crystal structure and magnetic properties are investigated by using the x-ray diffraction and magnetic measurements. The Rietveld structural analysis indicates that the ErGa_(3-x)Mn_x crystallizes into a cubic structure with space group of Pm3m in Mn doping range of x = 0–0.1. However, the disordered alloy with structural formula of Er_(0.8)Ga_2~Ⅰ(Ga~Ⅱ, Mn)0.4 as the second phase is separated from cubic phase for the samples with x = 0.2 and 0.3, which is induced by substituting the(Ga~Ⅱ, Mn)–(Ga~Ⅱ, Mn) pair at 2e crystal position for the rare earth Er at 1 a site. The lattice parameters tend to increase with Mn content increasing due to the size effect at Ga(1.30°A) site by substituting Mn(1.40°A) for Ga. The paramagnetic characteristic is observed by doping Mn into ErGa_3 at room temperature. With Mn content increasing from x = 0 to 0.1, the magnetic susceptibility χtends to increase. This phenomenon can be due to the increase of effective potential induced by doping Mn into ErGa_3.However, the magnetic susceptibility χ continues to decrease with the increase of Mn content in a range of x 0.2, which is due to the phase separation from the cubic Er(Ga, Mn)_3 to the hexagonal Er_(0.8)Ga_2(Ga, Mn)_(0.4).  相似文献   

10.
In this paper,we report on the influence of annealing treatment on as-grown Ib-type diamond crystal under high pressure and high temperature in a china-type cubic anvil high-pressure apparatus.Experiments are carried out at a pressure of 7.0 GPa and temperatures ranging from 1700 C to 1900 C for 1 h.Annealing treatment of the diamond crystal shows that the aggregation rate constant of nitrogen atoms in the as-grown Ib-type diamond crystal strongly depends on diamond morphology and annealing temperature.The aggregation rate constant of nitrogen remarkably increases with the increase of annealing temperature and its value in octahedral diamond is much higher than that in cubic diamond annealed at the same temperature.The colour of octahedral diamond crystal is obviously reduced from yellow to nearly colorless after annealing treatment for 1 h at 1900 C,which is induced by nitrogen aggregation in a diamond lattice.The extent of nitrogen aggregation in an annealed diamond could approach approximately 98% indicated from the infrared absorption spectra.The micro-Raman spectrum reveals that the annealing treatment can improve the crystalline quality of Ib-type diamond characterized by a half width at full maximum at first order Raman peak,and therefore the annealed diamond crystals exhibit nearly the same properties as the natural IaA-type diamond stones of high quality in the Raman measurements.  相似文献   

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