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1.
Using Mn + implantation following ion beam-induced epitaxial crystallization (IBIEC) annealing, high Curie temperature ferromagnetic (Ga,Mn)As thin film was fabricated. The crystalline quality of the Mn + implanted layer was identified by X-ray diffraction (XRD) and transmission electron microscopy (TEM). A clear ferromagnetic transition at Tc 253 K was observed by magnetization vs. temperature measurement. We infer that IBIEC treatment is a useful method not only for the low-temperature annealing of (Ga,Mn)As thin films but also for other dilute magnetic semiconductor (DMS) samples. 相似文献
2.
The magnetic and electrical properties of nonmagnetic Ga +3 ion substitution for Mn site are investigated in the bilayer manganite La 1.2 Sr 1.8 Mn 2 O 7.When the Mn is substituted by Ga,the ferromagnetic property obviously weakens,the magnetic transition temperature decreases and a spin-glass behaviour occurs at low temperature.Meanwhile,doping causes the resistivity to dramatically increase,the metal-insulator transition temperature to disappear,and a greater magneto-resistance effect to occur at low temperature.These effects result from the fact that Ga substitution dilutes the magnetic active Mn-O-Mn network and weakens the double exchange interaction,and further suppresses ferromagnetic ordering and metallic conduction. 相似文献
3.
Many studies have been done on low energy (1–200 keV) and high dose (10 16–10 17) implantation of Mn in GaAs. This study is an attempt to incorporate Mn ions in GaAs through implantation of 1 MeV Mn +1 ions in semi-insulating GaAs substrates at doses of 3×10 15/cm 2 and subsequent annealing. This was done to find out if any alloy of Mn–Ga–As, or binary compounds of Mn–Ga or Mn–As form
due to annealing of Mn +1 ions implanted in GaAs substrates. High Resolution XRD (HRXRD) performed before annealing shows a possibility of Ga–Mn–As
alloy formation, and after annealing at 800°C, except for GaAs main peaks no other phase peaks were detected. Scanning electron
microscopy (SEM) shows nanostructures of various dimensions which are thought to be formed due to the defects generated due
to implantation. Fourier Transform Infrared (FTIR) study shows the shift in bandgap due to Mn doping. Raman spectroscopy shows
the red shift in LO and TO peak positions of GaAs after annealing, which indicates the presence of disorder and damage due
to implantation. Resistivity measurement shows a thermally activated semiconductor character of charge conduction with an
activation energy of 51 meV and this activation may have occurred through the transitions from impurity band to valence band.
Large positive (∼25%) magnetoresistance and a mixture of ferromagnetic and paramagnetic behavior obtained in the magnetization
measurement indicate the presence of ferromagnetic MnAs nanoclusters embedded in paramagnetic GaAs:Mn matrix. 相似文献
4.
Thin metal-polymer composite films have been prepared by high-dose ion-beam implantation of Fe + and Co + ions into polyethylene terephthalate. The implantation of 40 keV ions at room temperature with doses from 2 · 10 16 to 4 · 10 17 cm −2 have been performed, with the ion current density of 4 μA/cm 2. The effects of implantation dose on the film morphology and crystal structure have been investigated via atomic force and
magnetic force microscopy and X-ray diffraction. The magnetic properties of synthesized structures have been studied by ferromagnetic
resonance and with a vibrating-sample magnetometer. It was established that the properties of ion-implanted samples strongly
depend on both the implantation dose and the type of implanted ions. The implantation dose at which the magnetic phase is
formed for iron-implanted samples is significantly lower than that for cobalt-implanted ones. At high implantation doses due
to polymer sputtering metal-containing layers are formed close to the sample surface for both ions. In this dose range the
magnetic properties of implanted samples changed dramatically due to particle oxidation. The coercivity of synthesized layers
reaches 180 and 300 Oe for iron- and cobalt-implanted samples, respectively.
Authors' address: Vladimir Yu. Petukhov, Kazan Physical-Technical Institute, Sibirskii trakt 10/7, 420029 Kazan, Russian Federation 相似文献
5.
We present the room-temperature ferromagnetism in the (Ga,Mn)N films grown on n-type GaN templates by plasma-enhanced molecular beam epitaxy for semiconductor spintronic device applications. Despite of the possible interface effects between the (Ga,Mn)N layers and n-type GaN templates, the (Ga,Mn)N films were found to exhibit the ferromagnetic ordering above room temperature. The magnetic force microscopy identified the magnetic domains with the different magnetic orientations at room temperature, indicating the existence of the ferromagnetic long-range ordering. In Raman spectra, an additional peak at 578 cm −1 was observed, which is attributed to the local vibration of substitutional Mn in the (Ga,Mn)N lattice. Therefore, it is believed that the ferromagnetic ordering in (Ga,Mn)N is due to the carrier-mediated Ruderman-Kittle-Kasuya-Yosida interaction. 相似文献
6.
The effects of 200 MeV Au ions irradiation on the structural and magnetic properties of Ni–Mn–Sn ferromagnetic shape memory alloy (FSMA) thin films have been systematically investigated. In order to understand the role of initial microstructure and phase of the film with respect to high energy irradiation, the two types of Ni–Mn–Sn FSMA films having different phases at room temperature were irradiated, one in martensite phase (Ni 58.9Mn 28.0Sn 13.1) and other in austenite phase (Ni 50Mn 35.6Sn 14.4). Transmission electron microscope (TEM) and scanning electron microscope (SEM) images along with the diffraction patterns of X-rays and electrons confirm that martensite phase transforms to austenite phase at a fluence of 6×10 12 ions/cm 2 and a complete amorphization occurs at a fluence of 3×10 13 ions/cm 2, whereas ion irradiation has a minimal effect on the austenitic structure (Ni 50Mn 35.6Sn 14.4). Thermo-magnetic measurements also support the above mentioned behaviour of Ni–Mn–Sn FSMA films with increasing fluence of 200 MeV Au ions. The results are explained on the basis of thermal spike model considering the core and halo regions of ion tracks in FSMA materials. 相似文献
7.
Samples of nanocomposite multiferroics have been synthesized by implantation of Co +, Fe +, and Ni + ions with an energy of 40 keV into ferroelectric barium titanate plates to doses in the range (0.5–1.5) × 10 17 ions/cm 2. It has been found that nanoparticles of metallic iron, cobalt, or nickel are formed in the barium titanate layer subjected to ion bombardment. With an increase in the implantation dose, the implanted samples sequentially exhibit superparamagnetic, soft magnetic, and, finally, strong ferromagnetic properties at room temperature. The average sizes of ion-synthesized 3 d-metal nanoparticles vary in the range from 5 to 10 nm depending on the implantation dose. Investigation of the orientation dependence of the magnetic hysteresis loops has demonstrated that the samples show a uniaxial (“easy plane”) magnetic anisotropy typical of thin granular magnetic films. Ferromagnetic BaTiO 3: 3 d metal samples are characterized by a significant shift of the ferromagnetic resonance signal in an external electric field, as well as by a large (in magnitude) magnetodielectric effect at room temperature. These results indicate that there is a strong magnetoelectric coupling between the ferroelectric barium titanate matrix and ion-synthesized nanoparticles of magnetic metals. 相似文献
8.
Correlations between crystal structures and magnetic properties of Fe 1–xMn x Pt films were studied. The disordered films with x ≥ 0.44 had paramagnetic properties and the ordered films with x ≥ 0.46 had antiferromagnetic properties, viz. a difference of 0.02 in the x ‐value (i.e., 1.0 at%) was found. At x = 0.44 with the ordered structure, the uniaxial magnetocrystalline anisotropy was about 2.1 × 10 7 erg cm –3. A microfabrication process involving the slight composition difference of 0.02, which results in ferromagnetic–paramagnetic phase change due to the structural transformation caused by ion irradiation, was investigated. Only the area irradiated by Mn ions changed from ferromagnetic to paramagnetic phase. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
9.
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
10.
LiFe 1 − xMn xPO 4 olivines are promising material for improved performance of Li‐ion batteries. Spin–phonon coupling of LiFe 1 − xMn xPO 4 ( x = 0, 0.3, 0.5) olivines is studied through temperature‐dependent Raman spectroscopy. Among the observed phonon modes, the external mode at ~263 cm −1 is directly correlated with the motions of magnetic Fe 2+/Mn 2+ ions. This mode displays anomalous temperature‐dependent behavior near the Néel temperature, indicating a coupling of this mode with spin ordering. As Mn doping increases, the anomalous behavior becomes clearly weaker, indicating the spin–phonon coupling quickly decreases. Our analyses show that the quick decrease of spin–phonon coupling is due to decrease of the strength of spin–phonon coupling, but not change of spin‐ordering feature with Mn doping. Importantly, we suggest that the low electrochemical activity of LiMnPO 4 is correlated with the weak spin–phonon coupling strength, but not with the weak ferromagnetic ground state. Our work would play an important role as a guide in improving the performances of future Li‐ion batteries. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
11.
Raman spectroscopy was used to study the evolution of host lattice recrystallization in Mn +-implanted GaAs. A high dose of Mn +-ions (>10 15 cm -2) was introduced into semi-insulating GaAs by the combinatorial implantation method. Subsequent thermal annealing at 920 °C
was carried out to re-grow the implantation-induced amorphous layers. The dependence of the recrystallization behavior on
the Mn content was systematically observed. The lattice orientation of recrystallized layers in the surface changed after
high-dose implantation (>1.6×10 15 cm -2) and annealing. The size of the recrystallized crystallites decreased with increasing Mn + dose, as indicated by images from atomic force microscopy. The decrease in the phonon frequency of the Raman lines with the
size reduction of microcrystals was in good agreement with the spatial correlation model. However, at higher doses (>7×10 16 cm -2), a blue shift of the frequency was observed due to the compressive stress exerted on the microcrystals.
Received: 5 March 2002 / Accepted: 29 August 2002 / Published online: 8 January 2003
RID="*"
ID="*"Corresponding author. Fax: +86-21/658-30734, E-mail: jqwang@mail.sitp.ac.cn 相似文献
12.
Mn site is substituted with closed shell ions (Al, Ga, Ti, Zr and a certain combination of Zr and Al) and also with Fe and
Ru ions carrying the magnetic moment ( S=5/2 and 2 respectively) at a fixed concentration of 5 at %. Substitution did not change either the crystal symmetry or the
oxygen stoichiometry. All substituents were found to suppress both the metal-insulator and ferromagnetic transition temperatures
( T
p( ρ) and T
C, respectively) to varied extents. Two main contributions identified for the suppression are the lattice disorder arising
due to difference in the ionic radii between the substituent ( r
M) and the Mn 3+ ion ( r
Mn
3+) and in the case of the substituents carrying a magnetic moment, the type of magnetic coupling between the substituent and
that of the neighboring Mn ion. 相似文献
13.
The structural, optical, and galvanomagnetic properties of (Ga, Mn)Sb layers grown by the laser sputtering of solid targets
in H 2 flow are n studied. It is shown that at a growth temperature of 400°C, (Ga, Mn)Sb layers are single-crystal up to high Mn
concentrations. The magnetic field dependence of the Hall resistance at measuring temperatures of 10–300 K contains a hysteresis
loop; i. e., the layers are ferromagnetic semiconductors. 相似文献
14.
The spin light-emitting diodes based on InGaAs/GaAs heterostructures with a quantum well and an injector in the form of a (Ga,Mn)As ferromagnetic layer have been studied. It has been demonstrated that the efficiency of electron spin injection in the structure with a (Ga,Mn)As/ n+-GaAs tunneling barrier can be controlled by varying the parameters of n+-GaAs. The spin injection control mechanisms associated with the thermal activation and tunneling of carriers have been discussed. 相似文献
15.
Mn doped TiO 2 nanoparticles are synthesized by sol–gel method. Incorporation of Mn shifts the diffraction peak of TiO 2 to lower angle. The position and width of the Raman peak and photoluminescence intensity of the doped nanoparticles varies with oxygen vacancy and Mn doping level. The electron spin resonance spectra of the Mn doped TiO 2 show peaks at g = 1.99 and 4.39, characteristic of Mn 2+ state. Reduction in the emission intensity, on Mn doping, is owing to the increase of nonradiative oxygen vacancy centers. Mn doped TiO 2, with 2% Mn, shows ferromagnetic ordering at low applied field. Paramagnetic contribution increases as Mn loading increases to 4% and 6%. Temperature dependent magnetic measurement shows a small kink in the ZFC curve at about 40 K, characteristic of Mn 3O 4. The ferromagnetic ordering is possibly due to the interaction of the neighboring Mn 2+ ions via oxygen vacancy ( F+ center). Increase in Mn concentration increases the fraction of Mn 3O 4 phase and thereby increases the paramagnetic ordering. 相似文献
16.
Mn-doped GaN films (Ga 1−xMn xN) were grown on sapphire (0 0 0 1) using Laser assisted Molecular Beam Epitaxy (LMBE). High-quality nanocrystalline Ga 1−xMn xN films with different Mn concentration were then obtained by thermal annealing treatment for 30 min in the ammonia atmosphere. Mn ions were incorporated into the wurtzite structure of the host lattice by substituting the Ga sites with Mn 3+ due to the thermal treatment. Mn 3+, which is confirmed by XPS analysis, is believed to be the decisive factor in the origin of room-temperature ferromagnetism. The better room-temperature ferromagnetism is given with the higher Mn 3+ concentration. The bound magnetic polarons (BMP) theory can be used to prove our room-temperature ferromagnetic properties. The film with the maximum concentration of Mn 3+ presents strongest ferromagnetic signal at annealing temperature 950 °C. Higher annealing temperature (such as 1150 °C) is not proper because of the second phase Mn xGa y formation. 相似文献
17.
Ion‐beam mixing of Fe–Mn bilayers induced by 100 keV krypton ions in the dose range (0.1-15)×10 15 ions/cm 2has been studied by means of conversion electron Mössbauer spectroscopy and X‐ray diffraction. The results indicate that a dose of about 1 ×10 15 Kr +/cm 2 is sufficient to induce an appreciable mixing between the two atomic species. The α-Fe(Mn)solid solution presents a maximum at this dose, while at higher doses also the ? and γFe–Mn phases are formed in an appreciable amount. Heating of irradiated samples evidences the metastable character of ? phase and favours the growth of the terminal structures γ-Fe(Mn) and α-Mn(Fe) of the Fe–Mn equilibrium phase diagram. 相似文献
18.
In the diluted magnetic semiconductor (Ga,Mn)As the excess of As incorporated as As antisites (As Ga) is responsible for the hole compensation. The As Ga defect can be transformed into a As interstitial–Ga vacancy pair (As i–V Ga) upon illumination. In this paper we study the effects of such a transition on the ferromagnetism of (Ga,Mn)As using density functional theory within the local spin density approximation. We find that the ferromagnetic order in (Ga,Mn)As is strongly enhanced if As Ga are transformed into As i–V Ga pairs, since the hole compensation is reduced. This suggests a valuable way to tune the carrier concentration and hence the Tc in (Ga,Mn)As, without changing the Mn concentration nor the microscopic configuration of the Mn ions. 相似文献
19.
It is shown that ZnO nanorods grown by MOCVD exhibit enhanced radiation hardness against high energy heavy ion irradiation as compared to bulk layers. The decrease of the luminescence intensity induced by 130 MeV Xe +23 irradiation at a dose of 1.5 × 10 14 cm –2 in ZnO nanorods is nearly identical to that induced by a dose of 6 × 10 12 cm –2 in bulk layers. The change in the nature of electronic transitions responsible for luminescence occurs at an irradiation dose around 1 × 10 14 cm –2 and 5 × 10 12 cm –2 in nanorods and bulk layers, respectively. High energy heavy ion irradiation followed by thermal annealing is also effective on the quality of ZnO nanorods grown by electrodeposition. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
20.
The effect of optical pumping and applied magnetic field on the characteristics of ferromagnetic layers in one-dimensional superlattices is studied. At low enough temperatures, these layers correspond to phase separation domains in RMn2O5 and R0.8Ce0.2Mn2O5 multiferroics. The formation of such domains occurs owing to the charge ordering of Mn3+ and Mn4+ ions and to the finite probability for eg electrons to tunnel between these pairs of ions. The volume occupied by such superlattices is rather small, and they can be treated as isolated ferromagnetic semiconductor heterostructures, spontaneously formed in the host crystal. The sequences of ferromagnetic resonances related to the superlattice layers in Eu0.8Ce0.2Mn2O5 are studied. The characteristics of these resonances give information on the properties of such layers. For the first time, it is demonstrated that the optical pumping gives rise to a new metastable state of superlattices, which can be recovered by the magnetic field cycling to the state existing before the optical pumping. It is found that the superlattices recovered by the magnetic field exist up to temperatures higher than those in as-grown crystals. 相似文献
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