共查询到20条相似文献,搜索用时 468 毫秒
1.
V. A. G. Rivera S. Sergeenkov C. Stari L. Cichetto C. A. Cardoso E. Marega F. M. Araujo-Moreira 《JETP Letters》2009,90(5):365-369
By applying a highly sensitive homemade AC susceptibility technique to Pr
x
Y1 − x
Ba2Cu3O7 − δ polycrystals (with x = 0.0, 0.1, and 0.3), we observed very sharp Fraunhofer type low-field periodic oscillations of the real part of the AC susceptibility
which were attributed to Josephson vortices penetrating intergranular regions of grain-boundary Josephson network in our samples.
Assuming the Lorentz type distribution of single-junction contact areas, we were able to successfully fit the experimental
data. 相似文献
2.
DC magnetization, neutron depolarization and neutron diffraction (with both polarized and unpolarized neutrons) measurements
have been reported for the Co1.1−x
Zn
x
Ge0.1Fe1.2O1 spinels with x=0.5, 0.6 and 0.7. Neutron depolarization and neutron diffraction measurements confirm the presence of a long range ferrimagnetic
ordering of the local canted spins in these ferrite samples. The observed features of low field magnetization have been explained
under the framework of thermally activated domain wall movement of ferrimagnetic arrangement of local canted spins. An important
role of magnetic anisotropy (due to the presence of Co2+ ions) in establishing the magnetic ordering and domain kinetics in these ferrites has been observed. 相似文献
3.
Neutron diffraction and magnetic methods are used to investigate ferrites from the system ZnxFe1−x
[Ni1−x
Fe1+x
]O4. In these investigations, no diffraction effects were observed that would indicate ordered positions for the perpendicular
projections of spins at 4.2 K over the entire ferrimagnetic range of concentrations x. However, the high-field magnetic susceptibility and intense small-angle scattering of neutrons observed at helium temperatures
in samples with x>0.45 are evidence of local angular structures with effective sizes of 1–10 nm. The temperatures at which these local angular
structures are disrupted are determined.
Fiz. Tverd. Tela (St. Petersburg) 40, 1503–1504 (August 1998) 相似文献
4.
Vasile Rednic Lidia Rednic Marin Coldea Viorel Pop Manfred Neumann Roxana Pacurariu Arthur R. Tunyagi 《Central European Journal of Physics》2008,6(3):434-439
X-ray photoelectron spectroscopy (XPS), magnetization and magnetic susceptibility of Mn1−x
Al
x
(x = 0.0, 0.2, 0.4, 0.5, 0.6, 0.7) alloys are reported. X-ray diffraction measurements showed that all investigated samples
have the same crystallographic structure as the parent compound (AuCu3-structure type). The alloys are disordered for x ≤ 0.5, but become almost crystallographically ordered for higher Al concentration.
This change in the crystallographic order is reflected both in the magnetization and Curie temperature values. The exchange
interaction is ferromagnetic between the pairs of the near-neighbour Mn-Ni and Ni-Ni magnetic moments and antiferromagnetic
for Mn-Mn pairs. The last one is present only in the disordered alloys, which leads to smaller values of the magnetization
of these alloys in comparison with the ordered ones. The Mn magnetic moment has the fully ordered value of 3.2 μB in all investigated
alloys. The decrease of the Ni magnetic moment as the Al concentration increases may be explained by the hybridization of
the Ni 3d and Al 3sp states, which leads to a partial filling of the Ni 3d band. The magnetic susceptibility measurements
pointed out the existence of spin fluctuations on Ni sites.
相似文献
5.
The electrical conductivity, magnetization, and magnetoresistance of manganites La1 − x
Ag
x
MnO3 have been investigated in the temperature range 78–300 K. The samples have been synthesized by the sol-gel method. At room
temperature, the magnetic field of 0.6 T has no effect on the electrical conductivity. As the temperature decreases, an abrupt
jump is observed in the magnetization curve due to the semiconductor-metal phase transition. This transition hardly affects
the temperature dependence of the resistance. 相似文献
6.
Mössbauer, X-ray, magnetization and susceptibility measurements were performed to study Fe100–x
Mn
x
,x=5, 15, 39, 50. The different phases of Fe-Mn were identified, and hyperfine interaction parameters and average magnetic moments of some samples were determined. The average hyperfine field and average magnetic moment decrease asx increases. The influence of the Mn neighbourhood on the derived parameters is discussed in the light of calculations using the first principle discrete variational method in the local density approximation. 相似文献
7.
A. I. Abramovich R. V. Demin L. I. Koroleva A. V. Michurin A. I. Smirnitskaya 《JETP Letters》1999,69(5):404-410
It is observed that low-temperature magnetic properties (dependence of the magnetization on the cooling conditions and the
presence of a maximum in the initial magnetic susceptibility) of Eu1− x
AxMnO3 (A=Ca, Sr; x=0,0.3) samples are similar to those of spin glasses. However, there are also substantial differences: The magnetization depends
on the cooling conditions right up to the maximum measurement fields H=45 kOe, and the temperature of T
N of the maximum of the initial magnetic susceptibility is independent of the frequency of the ac magnetic field in which the
susceptibility is measured. The magnetization isotherms for T<T
N are a superposition of a linear part, characteristic for an antiferromagnet, and a small spontaneous part. For compositions
containing Sr a maximum of the resistivity ρ (ρmax∼108 Ω ·cm) is observed near T
N; in a 120 kOe magnetic field this maximum is lowered by four orders of magnitude and the temperature of the maximum is two
times higher. In compositions with x=0.3 the paramagnetic Curie point is much higher than for the composition with x=0: θ=110 K (A=Ca), 175 K (A=Sr), and −100 K (x=0). These characteristic features of the magnetic and electric properties are explained by the existence of a magnetically
two-phase state in this system, consisting of ferromagnetic clusters, in which the charge carriers are concentrated, embedded
in an insulating antiferromagnetic matrix.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 5, 375–380 (10 March 1999) 相似文献
8.
S. Sambasivam D. Paul Joseph Jung Hyun Jeong Byung Chun Choi Kwon Taek Lim Sang Su Kim Tae Kwon Song 《Journal of nanoparticle research》2011,13(10):4623-4630
Diluted magnetic semiconductor (DMS) nanoparticles of Sn1−x
Er
x
O2 (x = 0.0, 0.02, 0.04, and 0.1) were prepared by sol–gel method. The X-ray diffraction patterns showed SnO2 rutile structure for all samples with no impurity peaks. The decrease in crystallite size with Er concentration was confirmed
from TEM measurements (from 12 to 4 nm). The UV–Visible absorption spectra of Er-doped SnO2 nanoparticles showed blue shift in band gap compared to undoped SnO2. The electron spin resonance analysis of Er-doped SnO2 nanoparticles indicate Er3+ in a rutile lattice and also decrease in intensity with Er concentration above x = 0.02. Temperature-dependent magnetization studies and the inverse susceptibility curves indicated increased antiferromagnetic
interaction with Er concentration. 相似文献
9.
S. Shamaila R. Sharif S. Riaz M. Khaleeq-ur-Rahman X. F. Han 《Applied Physics A: Materials Science & Processing》2008,92(3):687-691
Co
x
Pt1−x
(x≥0.7) alloy nanowires are grown into self-synthesized anodic alumina templates by electrodeposition. Magnetic and magnetization
properties of Co
x
Pt1−x
alloy nanowires are measured as functions of wire length, temperature, and field orientation. X-ray diffraction shows that
as-prepared CoPt nanowires are of fcc polycrystalline structure. A crossover of easy axis of magnetization is observed from
parallel to perpendicular of the nanowire axis as a function of length. The coercivity (H
c) and remanent squareness (SQ) of Co
x
Pt1−x
nanowire arrays are derived from hysteresis loops measured at various angles (θ) between the field and wire axis. H
c(θ) and SQ(θ) curves show bell-shaped or otherwise bell-shaped behavior corresponding to the easy axis of their magnetization. 相似文献
10.
We present theoretical analyses of anisotropic lattice diamagnetism, magnetization due to magnetic ions and carrier spin-polarization
in the diluted magnetic semiconductor, Pb1-x
Eu
x
Te. The lattice diamagnetism results from orbital susceptibility due to inter band effects and spin-orbit contributions. The
spin-orbit contribution is found to be dominant. However, both the contributions show pronounced anisotropy. With increase
in x, the diamagnetism decreases. We consider contributions from randomly distributed isolated magnetic ions and clusters of pairs
and triads for the local moment magnetization. The isolated magnetic-ion contribution is the dominant one.We calculate the
magnetization for two typical magnetic ion concentrations: x=0.03 and x=0.06. Temperature dependence of the magnetization is also considered. Apart from lattice and localized magnetic ions, the
carrier contribution to the spin-density is also calculated for a carrier density of p=1018 cm−3. the relative spin-density of carriers increases with increase in the magnetic field strength and magnetic ion concentration.
The agreement with experiment where available is reasonably good. 相似文献
11.
R. Z. Levitin A. S. Markosyan A. B. Petropavlovskii V. V. Snegirev 《Physics of the Solid State》1997,39(10):1633-1635
Measurements of magnetization in static fields up to 60 kOe and magnetic susceptibility in weak ac fields of the Y(Ni1−x
Mx)3 and Y2(Ni1−x
Mx)7 intermetallics (M=Fe and Cu, x
max=0.2), as well of the specific heat of these systems for some compositions are reported. It was found that these intermetallics
are ferromagnetic at low temperature, and that their spontaneous magnetizations M
s at 4.2 K and Curie temperatures T
C decrease monotonically with increasing copper concentration. The magnetic susceptibility of the Y(Ni1−x
Fex)3 system with 0.06≲x≲0.2 was observed to decrease rapidly with the temperature lowered below a characteristic temperature T
s. One of possible reasons for such an anomaly is shown to be the onset in this concentration region of the reentrant spin-glass
state at low temperatures. The results obtained demonstrate that the tight-binding d-band model fails to explain the evolution of the magnetic properties of YNi3 and Y2Ni7 in the case of small substitutions of iron and copper for nickel.
Fiz. Tverd. Tela (St. Petersburg) 39, 1828–1830 (October 1997) 相似文献
12.
The effect of Pr substitution for Dy on the magnetic and magnetostrictive properties, anisotropy, spin reorientation and M?ssbauer
effect of a series of Tb0.3Dy0.7−x
Pr
x
(Fe0.9Al0.1)1.95 (x=0, 0.1, 0.20, 0.25, 0.30, 0.35) alloys at room temperature have been investigated. It was found that a small amount of Pr
substitution is beneficial to a decrease in the magnetocrystalline anisotropy for the Tb0.3Dy0.7−x
Pr
x
(Fe0.9Al0.1)1.95 alloys. The magnetostriction decreases drastically with increasing x and the magnetostrictive effect disappears for x>0.2. However, the magnetostriction exhibits a slightly bigger value at x=0.1 than the free alloys and is saturated more easily with the magnetic field H. The saturation magnetization and Curie temperature decrease monotonously, but the spontaneous magnetostriction increases
linearly with increasing x, whereas the spin reorientation temperature increases first, then decreases rapidly and reaches the maximum at x=0.1. The analysis of M?ssbauer spectra indicated that the easy magnetization direction in the {110} plane deviates slightly
from the main axis of symmetry with the Pr concentration x, namely spin reorientation. Compared with Al substitution for Fe, the effect of Pr substitution for Dy on spin reorientation
is relatively small. The hyperfine field increases with Pr concentration increasing, and the isomer shifts and the quadrupole
splitting (QS) show weak concentration dependence.
Supported by the National Natural Science Foundation of China (Grant No. 10574059), the Natural Science Foundation of Gansu
Province (Grant No. 0710RJZA074), the Second Scientific Research Project of Bureau of Gansu Education and ‘Qing Lan’ Talent
Engineering Funds of Lanzhou Jiaotong University 相似文献
13.
A. Khajehnezhad N. Nikseresht H. Hadipour M. Akhavan 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(4):461-467
We have compared the electrical and magnetic properties of Ru(Gd1.5−x
Pr
x
)Ce0.5Sr2Cu2O10−δ
(Pr/Gd samples) with x = 0.0, 0.01, 0.03, 0.033, 0.035, 0.04, 0.05, 0.06, 0.1 and RuGd1.5(Ce0.5−x
Pr
x
) Sr2 Cu2O10−δ
(Pr/Ce samples) with x = 0.0, 0.01, 0.03, 0.05, 0.08, 0.1, 0.15, 0.2 prepared by the standard solid-state reaction technique. We obtained the XRD
patterns for different samples with various x. The lattice parameters versus x for different substitutions have been obtained from Rietveld analysis. To determine how the magnetic and superconducting
properties of these layered cuprate systems can be affected by Pr substitution, the resistivity, and magnetoresistivity, with
H
ext
varying from 0.0 to 15 kOe, have been measured at various temperatures. Superconducting transition temperature T
c
and magnetic transition T
irr
, have been obtained through resistivity and ac susceptibility measurements. The T
c
suppression due to Pr/Gd and Pr/Ce substitutions show competition between pair breaking by magnetic impurities, hole doping
due to different valances of ions, difference in ionic radii, and oxygen stoichiometry. Pr/Gd substitution suppresses superconductivity
more rapidly than for Pr/Ce, showing that the effect of hole doping and magnetic impurity pair breaking is stronger than the
difference in ionic radii. In Pr/Gd substitution, the small difference between the ionic radii of Pr3+,4+ and Gd3+, and absorption of more oxygen due to the higher valence of Pr with respect to Gd, decreases the mean Ru-Ru distance, and
as a result, the magnetic exchange interaction becomes stronger with the increase of x. However, Pr/Ce substitution has the opposite effect. The magnetic parameters such as H
c
, obtained through magnetization measurements versus applied magnetic field isotherm at 77 K and room temperatures, become
stronger with x in Pr/Gd and weaker with x in Pr/Ce substitution. 相似文献
14.
N. N. Efimova M. B. Ustimenkova 《Journal of Experimental and Theoretical Physics》1998,87(6):1122-1128
In connection with the problem of identifying magnetic states in the vicinity of x
0 (the multicritical point of the x-T diagrams of spin-glass systems) a study has been made of properties that can be exploited to determine the presence of a
thermodynamic phase transition at the Curie point T
C and the distinctive features of the transition, specifically, the temperature dependence of the magnetic part of the specific
heat C
m(T), the temperature dependence of the low-field magnetization σ
H(T), and (with a view toward examining critical behavior in a magnetic field) the magnetization isotherms σ
H(T). The investigated object is the system of dilute ferrimagnetic spinels Li0.5Fe2.5−x
GaxO4, in which every type of magnetic state has spatially inhomogeneous cluster structures. The results obtained for a sample
with x=1.45 indicate that the classical criteria of a ferrimagnetic second-order phase transition at T
C=(97±2) K occur for x∼x
0. The results of similar investigations for a sample with x=1.6, which exists in the cluster spin-glass state for T<T
f=22 K and in an uncorrelated cluster state of the superparamagnetic type for T>T
f, are also given for comparison with the preceding case.
Zh. éksp. Teor. Fiz. 114, 2065–2077 (December 1998) 相似文献
15.
I. D. Luzyanin V. A. Ryzhov S. M. Dunaevskii V. P. Khavronin I. I. Larionov A. V. Lazuta Yu. P. Chernenkov 《Physics of the Solid State》2000,42(2):298-304
The temperature and field behaviors of the linear and nonlinear responses to a weak ac magnetic field in the Sm1−x SrxMnO3 manganites with x=0.25, 0.3, and 0.4 have been investigated. It is found that the hysteresis of the second harmonic of magnetization in the dc magneticfield arises in the far-paramagnetic range at T≤180 K, whereas the hystereses of the linear susceptibility and the dc resistivity are observed at lower temperatures. This phenomenon is associated with the formation of macroscopic ferromagnetic (ferrimagnetic) domains in the paramagnetic matrix. The shape of the temperature dependence of the linear susceptibility at T>T c is determined by the degree of doping, and the susceptibility itself nonmonotonically depends on x. 相似文献
16.
S. A. Nikitin T. I. Ivanova I. G. Makhro Yu. A. Tskhadadze N. F. Vedernikov 《Physics of the Solid State》1997,39(2):284-287
The magnetic and crystalline properties of the polycrystalline compounds GdxLa1−x
FeSi (x=0, 0.1, 0.3, 0.45, 0.55, 0.65, 0.8, 1) and single crystal GdFeSi are studied. All the compounds have the CeFeSi tetragonal
structure. The temperature dependences of the magnetization and initial susceptibility show that ferromagnetic behavior is
characteristic of these compounds; the exception is the Pauli paramagnetic LaFeSi. Substitution of gadolinium by the nonmagnetic
lanthanum leads to a sharp drop in the Curie temperature T
c, and to a reduction in the saturation magnetic moment μ
0, effective magnetic moment μ
eff, and paramagnetic Curie temperature Θp. Measurements on single crystal GdFeSi imply that the easy magnetization axis of this compound is the c axis and the anisotropy field is H
a∼4 kOe. No magnetic moment was observed on the iron ion in any of these compounds.
Fiz. Tverd. Tela (St. Petersburg) 39, 325–329 (February 1997) 相似文献
17.
Results are presented of an investigation of the magnetic properties of dilute frustrated ferrimagnetic spinels Li0.5Fe2.5−x
GaxO4 (x=0.8–1.2), which characterize the main parameters of the ferrimagnetic state and provide evidence of local violation of collinear
spin ordering and frustrations. In particular, measurements were made of the concentration dependences of the magnetic moment
n
0(x) and the Curie point T
c
(x), the magnetization isotherms σ
T
(H) at T=4.2 K and H⩽10 kOe, and also the low-and high-field magnetization polytherms σ
H
(T). It was established that for x⩾0.8 in fields exceeding the technical saturation field H
s
∼2 kOe, the temperature dependences of the high-field magnetization σ
H
(T) between 4.2 and 230 K cannot be described by the Bloch T
3/2 law whereas this law is satisfied for undiluted Li spinel (x=0). Over the entire temperature range (4.2–230 K) the experimental curves σ
H
(T) may be approximated by σ
H
(T)=σ
0(1−AT
3/2 − BT
5/2) for x=0.8–1.0 and σ
H
(T)=σ
0[1−CT
3/2exp(μ(H−H
0)/k
B
T)] for x=1.1, 1.2, where μH
0∼15 K is the internal field produced by competition between exchange interactions and frustrations.
Fiz. Tverd. Tela (St. Petersburg) 40, 1075–1079 (June 1998) 相似文献
18.
H. R. Kerchner D. K. Christen J. R. Thompson T. Armstrong 《Czechoslovak Journal of Physics》1996,46(Z3):1763-1764
The hysteretic magnetization of an YBa2Cu3O7−δ crystal containing a high density of Y2BaCuOx precipitates was investigated by two-axis, quasistatic, de magnetometry. As the eff-axis applied magnetic fieldH was increased and the magnetization magnitude, decreased, its orientation approached a direction near the crystallinec axis. The bulk persistent currentsJ
p
predominately flowed parallel to the Cu−O planes for a wide range of temperature and applied field. Even forH almost perpendicular toc, where the deduced irreversibility line maximized as commonly observed, the resulting magnetization was observed to be within
15° of [001].
Managed by Lockheed Martin Energy Research Corp, under contract AC05-96OR22464 with the U. S. Dept. of Energy. 相似文献
19.
Anowar Tozri Moez Bejar Essebti Dhahri EL Kébir Hlil 《Central European Journal of Physics》2009,7(1):89-95
X-ray powder diffraction (XRD) and magnetic measurements were performed in order to investigate the effect of Na+ ion substitution for Ca2+ ions on the crystallographic structure, the character of magnetic ordering, and the effect of transition temperature in La0.7Ca0.3−x
Na
x
MnO3 manganites series (0 ⩽ × ⩽ 0.2). All samples crystallise in an orthorhombic structure with the Pnma space group. We have found a strong dependence of structural and magnetic properties on the cation-size disorder parameter
σ
2. The temperature dependence of magnetization of all samples obeys the Bloch T
3/2 law. The values of the spin wave constant at low temperature B increase with the increase of x and the Curie temperature decreases. It is concluded that the substitution of Ca by Na+ ions causes a decrease in total exchange integral Aof the samples.
相似文献
20.
Shashaank Gupta Shuvrajyoti Bhattacharjee Dhananjai Pandey Vipul Bansal Suresh K. Bhargava Ju Lin Peng Ashish Garg 《Applied Physics A: Materials Science & Processing》2011,104(1):395-400
We report an unusual behavior observed in (BiFeO3)1−x
–(PbTiO3)
x
(BF–xPT) thin films prepared using a multilayer chemical solution deposition method. Films of different compositions were grown
by depositing several bilayers of BF and PT precursors of varying BF and PT layer thicknesses followed by heat treatment in
air. X-ray diffraction showed that samples of all compositions show mixing of two compounds resulting in a single-phase mixture,
also confirmed by transmission electron microscopy. In contrast to bulk compositions, samples show a monoclinic (MA-type) structure suggesting disappearance of the morphotropic phase boundary (MPB) at x=0.30 as observed in the bulk. This is accompanied by the lack of any enhancement of the remanent polarization at the MPB,
as shown by the ferroelectric measurements. Magnetic measurements showed an increase in the magnetization of the samples with
increasing BF content. Significant magnetization in the samples indicates melting of spin spirals in the BF–xPT films, arising from a random distribution of iron atoms. Absence of Fe2+ ions was corroborated by X-ray photoelectron spectroscopy measurements. The results illustrate that thin film processing
methodology significantly changes the structural evolution, in contrast to predictions from the equilibrium phase diagram,
besides modifying the functional characteristics of the BP-xPT system dramatically. 相似文献