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1.
The magnetic, thermal, and transport properties of martensitic phase transformation in single crystal Co5Ni2Ga3 have been investigated. The single crystal Co5Ni2Ga3 shows martensitic transformation at 251 K on cooling and 254 K on warming. Large jumps in the temperature-dependent resistance
curve, temperature-dependent magnetization curve, and temperature-dependent thermal conductivity curve are observed at martensitic
transformation temperature (T
M). Negative magnetoresistance due to spin disorder scattering was observed in Co5Ni2Ga3 single crystal at all temperature range. The temperature-dependent negative magnetoresistance shows a peak at T
M, which indicates that the spin disorder increases in the process of phase transition. Co5Ni2Ga3 sample exhibits a temperature dependence of thermal conductivity κ(T) (dκ/dT > 0) due to electrons being above temperature 100 K. 相似文献
2.
K. P. Singh V. P. S. Awana S. Balamurugan M. Shahabuddin H. K. Singh M. Husain H. Kishan E. R. Bauminger I. Felner 《Journal of Superconductivity and Novel Magnetism》2008,21(1):39-44
Nano particle of Fe3O4 (nFe3O4) up to 6 at% were doped in the superconducting MgB2 samples. Despite the strong ferromagnetic nature of Fe3O4, both the ac susceptibility and the resistivity measurements show that up to 4 at% of Fe3O4, T
c
=38 K is not changed, whereas for 6% T
c
decreases by 6 K. This indicates that a low concentration of Fe does not substitute either the Mg or B sites and probably
occupies the intergrain spaces. For 0.5% doped Fe3O4, an increase in J
c
with respect to the pure MgB2 samples is observed in the lower field and temperature regions (H<2 T and 20 K) indicating an enhanced flux pinning and the magnetic activation, i.e., the interaction between the magnetic
dipole of Fe ion and the vortices is weak in comparison to the effective pinning potential. Whereas, at H>2 T, J
c
of the doped samples is always less than that of MgB2, and the activation is dominant in comparison with the effective pinning potential provided by the doping. Flux jumps are
observed in lower T and H regions for the samples doped up to 1% nFe3O4 only. Magnetization plots of higher Fe content samples exhibited clear paramagnetic background. Mossbauer measurements for
the higher (4, 6 at%) nFe3O4 doped MgB2 samples show that at RT, the hyperfine field for both samples is ∼100 kOe and ∼120 kOe at 90 K. This means that the nFe3O4 particles decompose and form possibly an intermetallic Fe-B phase in the matrix. 相似文献
3.
xBaTiO3 + (1 − x)Ni0.93Co0.02Cu0.05Fe2O4 (x = 0.5, 0.6, 0.7, 0.8) composites with ferroelectric–ferromagnetic characteristics were synthesized by the ceramic sintering
technique. The presence of constituent phases in the composites was confirmed by X-ray diffraction studies. The average grain
size was calculated by using a scanning electron micrograph. The dielectric characteristics were studied in the 100 kHz to
15 MHz. The dielectric constant changed higher with ferroelectric content increasing; and it was constant in this frequency
range. The relation of dielectric constant with temperature was researched at 1, 10, 100 kHz. The Curie temperature would
be higher with frequency increasing. The hysteresis behavior was studied to understand the magnetic properties such as saturation
magnetization (M
s). The composites were a typical soft magnetic character with low coercive force. Both the ferroelectric and ferromagnetic
phases preserve their basic properties in the bulk composite, thus these composites are good candidates as magnetoelectric
materials. 相似文献
4.
G. D. Nipan V. A. Ketsko A. I. Stognij A. V. Trukhanov T. N. Kol’tsova M. A. Kop’eva L. V. Elesina N. T. Kuznetsov 《Inorganic Materials》2010,46(4):429-433
Using pyrohydrolytic synthesis, we have obtained a continuous series of Mg(Fe1 − x
Ga
x
)2O4 + δ solid solutions, as checked by X-ray diffraction. The magnetization and coercivity of the samples have been determined from
field dependences in applied magnetic fields of ±5 T, and their conductivity has been assessed using current-voltage measurements
at 300 K in electric fields from −200 to +200 V. The effective band gap of the solid solutions has been evaluated from their
absorption spectra obtained by diffuse reflectance measurements. The optimal composition for spintronic applications is Mg(Fe0.8Ga0.2)2O4 + δ. 相似文献
5.
Caixuan Xu Anming Hu Naomichi Sakai Izumi Hirabayashi Mitsuru Izumi 《Journal of Superconductivity and Novel Magnetism》2007,20(4):309-314
Single domain GdBa2Cu7-δ (Gd123) bulk superconductors were fabricated in air by top-seeding melt-texture growth. Performance of the air-processed
Gd123 was successfully enhanced by addition of both BaCO3 and BaCuO2−x
, which suppress the formation of Gd1+x
Ba2−x
Cu3O7-δ solid solutions. The optimum doping amount ranges from 0.05 to 0.15, M BaCO3 and 0.05 to 0.1, M BaCuO2−x
per molar Gd123. The distribution of the second phase particles was observed by scanning electron microscopy. A narrow band
formed by Gd2BaCuO5 particle concentration appeared around the seeding zone in both a–b plane and c-growth sector in Gd123 single grain. Trapped magnetic field density reached 0.67, T for sample with 24 mm in diameter and
8, mm in thickness and a high critical current density J
c up to 91,200, A/cm2 was achieved at 77, K under self-field. 相似文献
6.
Xue Wang Chen Guo Hu Yi Xi Chuan Hui Xia Xiao Shan He 《Journal of Superconductivity and Novel Magnetism》2010,23(6):909-911
Al-doped Fe3O4 nanoparticles were synthesized for the first time via the Composite-Hydroxide-Mediated (CHM) method from Fe3O4 and Al2O3 without using any capping agent. The synthesis technique was one-step and cost effective. The obtained products were characterized
by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersion spectroscopy (EDS). Samples with a tunable
size of 500–1500 nm, 200–800 nm, and 100–700 nm could be obtained by adjusting the reaction time and temperature. Magnetic
property of the as-synthesized Al-doped Fe3O4 nanoparticles was investigated. Magnetic hysteresis loops measured in the field range of −10 kOe<H<10 kOe, indicated the ferromagnetic behavior with coercivity (H
c) of 470 and 110 Oe and remanence magnetization (M
r) of 13 and 6.4 emu/g at the temperature of 5 and 300 K, respectively. The saturation intensity (M
s) was 46.1 emu/g at 5 K, while it was about 43.6 emu/g at 300 K. 相似文献
7.
Liming Yu Jiujing Wang Shixun Cao Shujuan Yuan Jincang Zhang 《Journal of Materials Science》2007,42(14):5335-5339
The properties of light rare earth Nd substitution for heavy rare earth Dy in Dy3Fe5O12 (DyIG) garnet ferrite have been studied. The Nd
x
Dy3–x
Fe5O12 (x = 0, 0.25, 0.5, 0.75 and 1) (Nd:DyIG) garnet powders were prepared by sol–gel autocombustion followed by heat treatment.
The structure and the magnetic properties of the annealed powders were measured with X-ray diffraction (XRD), the Fourier
Transform Infrared (FT-IR) and the Physical Properties Measurement System (PPMS) techniques. The experimental results indicate
that a single Nd:DyIG garnet phase structure can be obtained after the samples annealed above 800 °C. With the Nd substitution
content increasing, the average lattice constants of the sample, the a−d super-exchange interaction strengthens and the magnetization of unit cell increase. The maximum saturation magnetization
is 13.86 emu/g for x = 1, and coercive force is about 136 Oe, for x = 0.75. The reason of increasing in magnetization with Nd substitution is also discussed. 相似文献
8.
Nb3+-substituted garnet nanoparticles Y3−xNdxFe5O12 (x = 0.0, 0.5, 1.0, 1.5, and 2.0) were fabricated by a sol-gel method and their crystalline structures and magnetic properties
were investigated by using X-ray diffraction (XRD), thermal analysis (DTA/TG), and vibrating sample magnetometer (VSM). The
XRD patterns of Y3−xNdxFe5O12 have only peaks of the garnet structure and the sizes of particles range from 34 to 70 nm. From the results of VSM, it is
shown that when the Nd concentration x ( 1.0, the saturation magnetization of Y3−xNdxFe5O12 increases as the Nd concentration (x) is increased, and gets its maximum at x = 1.0, but when x ( 1.0, the saturation magnetization
decreases with increasing the Nd concentration (x), this may be due to the distortion of the microstructure of Y3−xNdxFe5O12, which leads to the decrease of the effective moment formed by Fe3+. Meanwhile, it is observed that with the enhancement of the surface spin effects, the saturation magnetization rises as the
particle size is increased. 相似文献
9.
Yu Cheng Lai Yen Hwei Chang Yen Chia Chen Hui-Jan Lin Guo Jo Chen 《Journal of Materials Science》2007,42(16):6887-6894
This study investigates how the addition of Co to a Fe59Pt41 alloy with compositions in the range of Fe59Pt41–Co59Pt41 affects the crystallographic ordering temperatures and magnetic properties of sputter-deposited films. Introducing Co into
the (Fe1−x
Co
x
)59Pt41 film affects the activation energy of atomic migration and grain growth, thus leading to a higher annealing temperature of
the L10 phase formation. At a Co concentration of x = 0.2, the saturation magnetization was maximum, at 1,480 emu/cm3, and the (Fe0.8Co0.2)59Pt41 film exhibited a coercivity of about 4 kOe. 相似文献
10.
Fe
x
Pt100−x
(70.1 ≤ x ≤ 83.4) thin films with ordered Fe3Pt phase were grown successfully onto MgO(110) substrates by electron beam evaporation. The unit cell of ordered Fe3Pt phase is elongated along c-axis direction and the thin films become more chemically ordered with decreasing Fe content. The magnetization of thin films
shows a decrease when Fe content is around 79 at.%. The relationship between magnetic anisotropy and structural parameters
suggests that the change of magnetic anisotropy in ordered Fe3Pt thin films with different compositions most likely stems from the magnetocrystalline origin. 相似文献
11.
Hideki Taguchi Sho Matsuoka Masaki Kato Ken Hirota 《Journal of Materials Science》2009,44(21):5732-5736
Perovskite-type (La1−x
Nd
x
)CoO3 was synthesized using citric acid at 700 °C. The Rietveld method indicated that the crystal structure changed from a rhombohedral
to an orthorhombic system at x = 0.4. The Co–O distance of the rhombohedral structure connected continuously with the average Co–O(2) distance of the orthorhombic
structure, and the Co–O–Co angle of the rhombohedral structure and the Co–O(2)–Co angle of the orthorhombic structure were
continuous. The average particle size of the samples was approximately 55 nm. CH4 oxidation started above 300 °C, and the temperature corresponding to the 50% conversion (T
1/2) of CH4 increased linearly with increases in x. It is considered that the amount of adsorbed oxygen decreased in response to the steric hindrance, and that T
1/2 increased as a result. 相似文献
12.
B. B. Straumal B. Baretzky O. A. Kogtenkova A. B. Straumal A. S. Sidorenko 《Journal of Materials Science》2010,45(8):2057-2061
The microstructure of binary Al100−x
–Mg
x
(x = 10, 15, 18 and 25 wt%) alloys after long anneals (600–4000 h) was studied between 210 and 440 °C. The transition from incomplete
to complete wetting of Al/Al grain boundaries (GBs) by the second solid phase Al3Mg2 has been observed. The portion of completely wetted GBs increases with increasing temperature beginning from T
wsmin = 220 °C. Above T
wsmax = 410 °C all Al/Al GBs are completely wetted by the Al3Mg2 phase. 相似文献
13.
The superconducting properties of iodine-intercalated high-temperature superconducting Bi2Sr2Ca2Cu3O10+x
phase (Bi-2223) were systematically studied. It was found that for samples containing a significant amount of Bi2Sr2CaCu2O8+x
, iodine intercalation results in the dramatic decrease of the inter-granular critical current density, as well as a significant
decrease of the critical temperature (T
c), the critical current density in the grains (J
cg), and of the amount of Bi-2223. For samples with a large amount of Bi-2223, T
c changes insignificantly, whereas J
cg can even increase. We argue that the different behavior of the superconducting parameters is the result of various oxygen
concentrations, and we explain the effect of iodine intercalation based on the parabolic dependence between T
c and the number of holes per CuO2 layer. The H(T) curves (determined from the peak position in the loss signal of ac susceptibility) for intercalated samples deviate significantly
from the quasi 2D-like behavior, pointing toward an enhancement of the 3D fluctuations of vortices. For the change in the
values and dimensionality of the flux pinning in the process of the intercalation, we attempted a qualitative explanation
based on the models proposed in literature. 相似文献
14.
Shubhra Kakani M. L. Kalra S. L. Kakani 《Journal of Superconductivity and Novel Magnetism》2008,21(5):301-311
The emergence of pressure induced superconductivity (SC) under the background of ferromagnetic state in 5f-electron based itinerant ferromagnetic superconductor UGe2 is studied in the single band model by using a mean-field approximation. The solutions to the coupled equations of superconducting
gap (Δ) and magnetization (m) are obtained using Green’s function technique and equation of motion method. It is shown that there generally exists a coexistent
(Δ≠0, m≠0) solution to the coupled equations of the order parameters in the temperature range 0<T<min (T
C,T
FM), where T
C and T
FM are respectively the superconducting and ferromagnetic transition temperatures. The study of electronic specific heat (C/T), density of states, free energy, etc. are also presented. The specific heat capacity at low temperature shows linear temperature
dependence as opposed to the activated behavior. Density of states increases as opposed to the case of a standard ferromagnetic
metal. Free energy study reveals that the superconducting ferromagnetic state has lower energy than the normal ferromagnetic
state and, therefore, realized at low enough temperature. The agreement between theory and experimental results for UGe2 is quite satisfactory.
相似文献
15.
Y. Y. Zhou X. Liu J. K. Furdyna M. A. Scarpulla O. D. Dubon 《Journal of Superconductivity and Novel Magnetism》2010,23(1):87-90
We present a ferromagnetic resonance (FMR) study of Ga1−x
Mn
x
As fabricated by Mn ion implantation (II) into (311) GaAs wafers followed by pulsed-laser melting (PLM). We measured the angular
dependence of FMR at 4 K, and the data were then fitted by Stoner–Wohlfarth model to obtain the cubic and uniaxial anisotropy
parameters. The observed angular behavior of FMR can be understood in terms of two contributions: a cubic anisotropy field
parallel to the 〈001〉 axes, and a uniaxial anisotropy field parallel to the [311] direction. Our results show that the magnetic
anisotropy fields in II-PLM (Ga,Mn)As are fundamentally similar to those in Ga1−x
Mn
x
As samples grown by molecular beam epitaxy (MBE), indicating that the two different growth methods lead to materials with
very similar magnetic properties. 相似文献
16.
V. M. Pan A. A. Kalenyuk A. L. Kasatkin O. M. Ivanyuta G. A. Melkov 《Journal of Superconductivity and Novel Magnetism》2007,20(1):59-69
Microwave surface impedance, Z
s(T), of epitaxial YBCO thin films deposited on CeO2-buffered sapphire substrates, was measured at several discrete frequencies within the range 5–134 GHz by use of coplanar
resonator and end-plate cavity resonator techniques. The main features of obtained experimental results are as follows: (i)
surface resistance R
s(T) at low temperatures obeys the exponential law: R
s(T) = R
res+R
0⋅exp [−δ/T] with a small gap δ value (δ≈ 0.7 T
c); (ii) the most perfect quasi-single-crystalline films reveal a distinct two-peak structure of R
s(T) dependence, which is not observable in films with a less ordered crystal structure. These features are believed to reveal
some intrinsic electron properties of such films, namely: (i) mixed (d+is) type symmetry of electron pairing, and (ii) dominant role of extended c-oriented defects (e.g., edge dislocation arrays or twin planes) in quasiparticles scattering for the most perfect films,
which demonstrate the two-peak anomalous R
s(T) behavior. 相似文献
17.
Zong-Yang Shen Yue-Ming Li Liang Jiang Run-Run Li Zhu-Mei Wang Yan Hong Run-Hua Liao 《Journal of Materials Science: Materials in Electronics》2011,22(8):1071-1075
Lead-free (1-x)K0.49Na0.51NbO3-xLiNbO3 (KNN-LN, x = 0 ~ 0.08) piezoelectric ceramics were prepared by the conventional solid-state sintering method. The effects of LiNbO3 doping amount x on the phase transition behavior and the electrical properties of KNN-LN ceramics were investigated. By increasing LiNbO3 doping amount x, the orthorhombic-tetragonal polymorphic phase transition (PPT) temperature (T
o–t) of KNN-LN ceramics shifted downwards, however, the Curie temperature (T
c) slightly moved upwards. The room temperature phase structure thus changed from orthorhombic to tetragonal across the compositions
with 0.05 ≤ x ≤ 0.06, named as PPT region. The composition with x = 0.06 in the tetragonal side of PPT region exhibited optimized electrical properties of d
33 = 246pC/N, k
p = 41.6%, ε
r = 679, tgδ = 0.028, and Q
m = 52. In addition to its very high T
c = 467 °C, this ceramic can be an excellent candidate for replacing the lead-based piezoceramics in high temperature applications. 相似文献
18.
A. V. Semeno A. A. Pronin N. E. Sluchanko N. A. Samarin A. V. Kuznetsov S. V. Demishev 《Journal of Superconductivity and Novel Magnetism》2007,20(2):109-112
Electron spin resonance of a single crystal of CuGeO3 doped with 2% of Co has been studied at f = 99 GHz in temperature range 1.8–50 K. Contributions to ESR absorption from Cu2+ chains and from Co2+ ions were derived. It is found that functions obtained for ESR integrated intensities: Curie-Weiss for Cu2+ (χCu ∼ C
Cu/(T + Θ), with Θ = 92 K) and Curie for Co2+ (χCo ∼ C
Co/T) are well consistent with temperature dependence of static magnetic susceptibility. Strong dependence of ESR absorption on
polarization of oscillating magnetic field was discovered for Co2+ contribution. Polarization effect was studied for magnetic field applied along a, b and c directions. Values of g-factors of resonance lines are presented. 相似文献
19.
I. Ardelean R. Lungu P. Păşcuţă 《Journal of Materials Science: Materials in Electronics》2007,18(8):837-841
Glasses of the xFe2O3·(100−x)[B2O3·SrO] system, with 0 ≤ x ≤ 30 mol% were studied by X-ray diffraction, density, optical microscopy and FT-IR spectroscopy measurements. The X-ray patterns
for the prepared system show that vitreous phase is present only in the sample with x < 40 mol%. For x ≥ 40 mol% in the studied samples is evidenced crystalline phase of Fe2O3. SEM measurements for the sample with x = 40 mol% shows that there are formed Fe2O3 microcrystallites with 10–20 μm dimension. FT-IR spectroscopy measurements shown that BO3 and BO4 are the main structural units of the glass system and the iron ions are located in the glass network. 相似文献
20.
Jie Su Xiaomei Lu Chao Zhang Junting Zhang Song Peng Xiaobo Wu Kangli Min Fengzhen Huang Jinsong Zhu 《Journal of Materials Science》2011,46(10):3488-3492
Ho3Fe5O12 ceramics were fabricated by the solid-state reaction method. The results revealed an increase of the grain size, dielectric
constant, and dielectric loss, while a decrease of the remnant magnetization and coercive field with increasing sintering
temperature. A dielectric relaxation behavior was observed, which might be associated with the charge carrier hopping between
Fe2+ and Fe3+. A cole–cole fitting to loss peaks revealed a dependence of the activation energy and the broaden factor on the relative density of the
samples. Furthermore, at appropriate frequencies, the 1250 °C-sintered samples showed high dielectric constant, low dispassion,
and good temperature stability around room temperature. 相似文献