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1.
Influence of magnetic field sweep rate on the hysteresis loops of Ni0.8Fe0.2/Fe0.5Mn0.5 exchange bias bilayer 下载免费PDF全文
The influence of the magnetic field sweep rate on the hysteresis loops of exchange bias Ni0.8Fe0.2/Fe0.5Mn0.5 bilayers has been investigated with a vibrating sample magnetometer. It was found that the sweep rate of 13.6 kA/4πms is high enough to bring about obvious changes in the hysteresis loops of the exchange bias bilayer. High sweep rate in the magnetization reversal stage enlarges the coercivity of the sample, while high sweep rate in the saturation state reduces the coercivity. The above phenomena were attributed to magnetic viscosity in the ferromagnetic layer enhanced by the interface exchange interaction and domain magnetization reversals assisted by thermal fluctuation in the antiferromagnetic layer respectively. 相似文献
2.
The magnitude of the exchange bias (EB) effect in nanogranular Ni/NiO samples (with Ni content between about 4 and 69 wt% and mean size of the Ni crystallites of the order of 10 nm) has been found to be strictly related to the increase in the remanent magnetization measured after field-cooling, with respect to the value after zero-field-cooling, normalized to the saturation magnetization. This allows describing the EB mechanism in terms of the fraction of the magnetic moments of the Ni nanocrystallites that irreversibly has aligned in the field direction during field-cooling, due to the exchange anisotropy, and that is effectively involved in the loop shift. Hence, the possibility of tuning EB by controlling the field-cooled remanent magnetic state is shown. 相似文献
3.
研究了交换偏置双层膜中界面存在二次以及双二次交换耦合下反铁磁磁矩转动及其交换各向异性.结果表明,其反铁磁膜中的磁矩转动存在可逆“恢复行为”、不可逆“半转动行为”、不可逆“倒转行为”以及不可逆“半倒转行为”四种情形,四种情形的出现强烈地依赖于界面二次、双二次耦合以及反铁磁膜厚度.其中可逆恢复行为情况下,系统出现交换偏置,而不可逆的半转、半倒转以及倒转情形,系统不出现交换偏置.特别地,在界面处仅存在双二次耦合的情形下,其界面双二次耦合常数J2≤0.1 σ关键词:
反铁磁自旋结构
交换各向异性
界面双二次耦合
交换偏置 相似文献
4.
The magnetization curves along the crystal axes for Gd_2Fe_{17} and Gd_2Fe_{17}H_3 were analysed based on the single-ion model. If the Gd-Fe exchange interaction has been taken as isotropic as usual, the fitted values of magneto-crystalline anisotropy of the Fe sublattices in Gd_2Fe_{17} and Gd_2Fe_{17}H_3 would become unreasonably different from those of the corresponding Y or Lu compounds. It was shown that the large difference is caused by the neglect of the anisotropy of the Gd-Fe exchange interaction. 相似文献
5.
The static and dynamic magnetic properties of a Prussian blue analogue, molecular magnet Cu^Ⅱ_{3}[Fe^Ⅲ(CN)_6]_2·3NH_3·6H_2O were investigated in detail. The H dependence of the linear AC susceptibility, the irreversibility in the field-cooled (FC)/zero-field-cooled (ZFC) magnetization (M_{FC}/M_{ZFC}) and the relaxation of M_{ZFC} suggest that the magnetic system can be visualized as containing a ferromagnetic cluster of spin below T_C, mixed with small spin-glass clusters formed below temperature T_g less than T_C. The observed magnetic properties are explained with a ferromagnetic-spin-glass phase model. The magnetic ordering of the sample occurs below 19.8K. 相似文献
6.
The structure dependence of exchange bias in ferromagnetic/antiferromagnetic (FM/AF) bilayers has been investigated in detail by extending Slonczewski's 'proximity magnetism' idea. Here three important parameters are discussed for FM/AF bilayers, i.e. interracial bilinear exchange coupling J1, interracial biquadratic (spin-flop) exchange coupling J2 and antiferromagnetic layer thickness tAF. The results show that both the occurrence and the variety of the exchange bias strongly depend on the above parameters. More importantly, the small spin-flop exchange coupling may result in an exchange bias without the interracial bilinear exchange coupling. However, in general, the spin-flop exchange coupling cannot result in the exchange bias. The corresponding critical parameters in which the exchange bias will occur or approach saturation are also presented. 相似文献
7.
We report the results of magnetization and specific heat measurements on Ba{3}CoSb{2}O{9}, in which the magnetic Co{2+} ion has a fictitious spin 1/2, and provide evidence that a spin-1/2 Heisenberg antiferromagnet on a regular triangular lattice is actually realized in Ba{3}CoSb{2}O{9}. We found that the entire magnetization curve including the one-third quantum magnetization plateau is in excellent quantitative agreement with the results of theoretical calculations. We also found that Ba{3}CoSb{2}O{9} undergoes a three-step transition within a narrow temperature range. 相似文献
8.
Filibian M Carretta P Mozzati MC Ghigna P Zoppellaro G Ruben M 《Physical review letters》2008,100(11):117601
Nuclear magnetic resonance, electron paramagnetic resonance and magnetization measurements show that bulk LixZnPc are strongly correlated one-dimensional metals. The temperature dependence of the nuclear spin-lattice relaxation rate 1/T_{1} and of the static uniform susceptibility chi_{S} on approaching room temperature are characteristic of a Fermi liquid. Moreover, while for x approximately 2 the electrons are delocalized down to low temperature, for x-->4 a tendency towards localization is noticed upon cooling, yielding an increase both in 1/T_{1} and chi_{s}. The x dependence of the effective density of states at the Fermi level D(E_{F}) displays a sharp enhancement for x approximately 2, at the half filling of the ZnPc lowest unoccupied molecular orbitals. This suggests that LixZnPc is on the edge of a metal-insulator transition where enhanced superconducting fluctuations could develop. 相似文献
9.
Magnetization and magnetic phase diagrams of a spin-1/2 ferrimagnetic diamond chain at low temperature 下载免费PDF全文
《中国物理 B》2021,30(5):57503-057503
We used the Jordan–Wigner transform and the invariant eigenoperator method to study the magnetic phase diagram and the magnetization curve of the spin-1/2 alternating ferrimagnetic diamond chain in an external magnetic field at finite temperature. The magnetization versus external magnetic field curve exhibits a 1/3 magnetization plateau at absolute zero and finite temperatures, and the width of the 1/3 magnetization plateau was modulated by tuning the temperature and the exchange interactions. Three critical magnetic field intensities H_(CB), H_(CE) and H_(CS) were obtained, in which the H_(CB) and H_(CE) correspond to the appearance and disappearance of the 1/3 magnetization plateau, respectively, and the higher H_(CS) correspond to the appearance of fully polarized magnetization plateau of the system. The energies of elementary excitation ωσ,k(σ = 1, 2, 3) present the extrema of zero at the three critical magnetic fields at 0 K, i.e., [hω_(3,k)(HCB)]_(min)= 0, [hω_(2,k)(H_(CE))]_(max)= 0 and [hω _(2,k)(H_(CS))]_(min)= 0, and the magnetic phase diagram of magnetic field versus different exchange interactions at 0 K was established by the above relationships. According to the relationships between the system's magnetization curve at finite temperatures and the critical magnetic field intensities, the magnetic field-temperature phase diagram was drawn. It was observed that if the magnetic phase diagram shows a three-phase critical point, which is intersected by the ferrimagnetic phase, the ferrimagnetic plateau phase, and the Luttinger liquid phase, the disappearance of the1/3 magnetization plateau would inevitably occur. However, the 1/3 magnetization plateau would not disappear without the three-phase critical point. The appearance of the 1/3 magnetization plateau in the low temperature region is the macroscopic manifestations of quantum effect. 相似文献
10.
Alexandra Mougin Stéphane Mangin Jean-Francois Bobo Alois Loidl 《The European Physical Journal B - Condensed Matter and Complex Systems》2005,45(2):155-155
The study of layered magnetic structures is one of the hottest topics in magnetism due to the growing attraction of
applications in magnetic sensors and magnetic storage media, such as random access memory. For almost half a century,
new discoveries have driven researchers to re-investigate magnetism in thin film structures. Phenomena such as giant
magnetoresistance, tunneling magnetoresistance, exchange bias and interlayer exchange coupling led to new ideas to
construct devices, based not only on semiconductors but on a variety of magnetic materials
Upon cooling fine cobalt particles in a magnetic field through the Néel temperature of their outer antiferromagnetic
oxide layer, Meiklejohn and Bean discovered exchange bias in 1956. The exchange bias effect through which an
antiferromagnetic AF layer can cause an adjacent ferromagnetic F layer to develop a preferred direction of
magnetization, is widely used in magnetoelectronics technology to pin the magnetization of a device reference layer in a
desired direction. However, the origin and effects due to exchange interaction across the interface between
antiferromagneic and ferromagnetic layers are still debated after about fifty years of research, due to the extreme
difficulty associated with the determination of the magnetic interfacial structure in F/AF bilayers. Indeed, in an AF/F
bilayer system, the AF layer acts as “the invisible man” during conventional magnetic measurements and the presence of
the exchange coupling is evidenced indirectly through the unusual behavior of the adjacent F layer. Basically, the
coercive field of the F layer increases in contact with the AF and, in some cases, its hysteresis loop is shifted by an
amount called exchange bias field. Thus, AF/F exchange coupling generates a new source of anisotropy in the F layer. This
induced anisotropy strongly depends on basic features such as the magnetocrystalline anisotropy, crystallographic and spin
structures, defects, domain patterns etc of the constituant layers.
The spirit of this topical issue is, for the first time, to gather and survey recent and original
developments, both experimental and theoretical, which bring new insights into the physics of exchange bias. It has been
planned in relation with an international workshop exclusively devoted to exchange bias, namely IWEBMN’04 (International
Workshop on Exchange Bias in Magnetic Nanostructures) that took place in Anglet, in the south west of France, from
16th to 18th September 2004. The conference gathered worldwide researchers in the area, both
experimentalists and theoreticians. Several research paths are particularly active in the field of magnetic exchange
coupling. The conference, as well as this topical issue, which was also open to contributions from scientists
not participating in the conference, has been organized according to the following principles:
1. Epitaxial systems:
Since the essential behavior of exchange bias critically depends on the atomic-level chemical and spin structure at the
interface
between the ferromagnetic and antiferromagnetic components, epitaxial AF/F systems in which the quality of the interface and
the
crystalline coherence are optimized and well known are ideal candidates for a better understanding of the underlying physics
of
exchange bias. The dependence of exchange bias on the spin configurations at the interfaces can be accomplished by selecting
different crystallographic orientations. The role of interface roughness can also be understood from thin-film systems by
changing the growth parameters, and correlations between the
interface structure and exchange bias can be made, as reported in this issue.
2. Out-of-plane magnetized systems:
While much important work has been devoted to the study of structures with in-plane magnetization, little has been done
on the study of exchange bias and exchange coupling in samples with out-of-plane magnetization. Some systems can exhibit
either in-plane or out-of-plane exchange bias, depending on the field cooling direction. This is of particular interest
since it allows probing of the three-dimensional spin structure of the AF layer. The interface magnetic configuration is
extremely important in the perpendicular geometry, as the short-range exchange coupling competes with a long-range
dipolar interaction; the induced uniaxial anisotropy must overcome the demagnetization energy to establish perpendicular
anisotropy films. Those new studies are of primary importance for the magnetic media industry as perpendicular recording
exhibits potential for strongly increased storage densities.
3. Parameters tuning exchange bias in polycrystalline samples and magnetic configurations:
Different parameters can be used to tune the exchange bias coupling in polycrystalline samples similar to those used in
devices. Particularly fascinating aspects are the questions of the appearance of exchange bias or coercivity in
ferromagnet/antiferromagnet heterostructures, and its relation to magnetic configurations formed on either side of the
interface. Several papers report on either growth choices or post preparation treatments that enable tuning of the exchange
bias in bilayers. The additional complexity and novel features of the exchange coupled interface make the problem
particularly rich.
4. Dynamics and magnetization reversal:
Linear response experiments, such as ferromagnetic resonance, have been used with great success to identify interface,
surface anisotropies and interlayer exchange in multilayer systems. The exchange bias structure is particularly well
suited to study because interface driven changes in the spin wave frequencies in the ferromagnet can be readily related
to interlayer exchange and anisotropy parameters associated with the antiferromagnet. Because the exchange bias is
intimately connected with details of the magnetization process during reversal and the subsequent formation of
hysteresis, considerations of time dependence and irreversible processes are also relevant. Thermal processes like the
training effect manifesting itself in changes in the hysteretic characteristics depending on magnetic history can lead to
changes in the magnetic configurations. This section contains an increasing number of investigations of dynamics in
exchange bias coupled bilayers, and in particular those of the intriguing asymmetric magnetization reversal in both
branches of a hysteresis loop.
The Editors of the topical issue:
Alexandra Mougin
Laboratoire de Physique des Solides, UMR CNRS 8502, Université Paris Sud, F-91405 Orsay, France
Stéphane Mangin
Laboratoire de Physique des Matériaux, UMR CNRS 7556, Université Henri Poincaré, F-54506 Nancy, France
Jean-Francois Bobo
Laboratoire de Physique de la Matière Condensée - NMH, FRE 2686 CNRS ONERA, 2 avenue Edouard Belin,
F-31400 Toulouse, France
Alois Loidl
Experimentalphysik V, EKM, Institut für Physik, Universität Augsburg, Universitätsstrasse 1, D-86135, Augsburg, Germany 相似文献
11.
Magnetotransport properties and magnetocaloric effects of Mn1.95Cr0.05Sb0.95Ga0.05 compound 下载免费PDF全文
The magnetotransport properties and magnetocaloric effects of the compound Mn_{1.95}Cr_{0.05}Sb_{0.95}Ga_{0.05} have been studied. With decreasing temperature, a spontaneous first-order magnetic phase transition from ferrimagnetic (FI) to antiferromagnetic (AF) state takes place at T_s=200K. A metamagnetic transition from the AF to FI state can be induced by an external field, accompanied by a giant magnetoresistance effect of 57%. The magnetic entropy changes are determined from the temperature and field dependence of the magnetization using the thermodynamic Maxwell relation. Mn_{1.95}Cr_{0.05}Sb_{0.95}Ga_{0.05} exhibits a negative magnetocaloric effect, and the absolute values of ΔS_M^{max}(T,ΔH) are 4.4, 4.1, 3.6, 2.8 and 1.5 J/(kg·K) for magnetic field changes of 0-5T, 0-4T, 0-3T, 0-2T and 0-1T, respectively. 相似文献
12.
Béa H Bibes M Ott F Dupé B Zhu XH Petit S Fusil S Deranlot C Bouzehouane K Barthélémy A 《Physical review letters》2008,100(1):017204
We have combined neutron scattering and piezoresponse force microscopy to show that the exchange field in CoFeB/BiFeO_{3} heterostructures scales with the inverse of the ferroelectric and antiferromagnetic domain size of the BiFeO3 films, as expected from Malozemoff's model of exchange bias extended to multiferroics. Accordingly, polarized neutron reflectometry reveals the presence of uncompensated spins in the BiFeO3 film at the interface with CoFeB. In view of these results, we discuss possible strategies to switch the magnetization of a ferromagnet by an electric field using BiFeO3. 相似文献
13.
Aaltonen T Abulencia A Adelman J Affolder T Akimoto T Albrow MG Amerio S Amidei D Anastassov A Anikeev K Annovi A Antos J Aoki M Apollinari G Arisawa T Artikov A Ashmanskas W Attal A Aurisano A Azfar F Azzi-Bacchetta P Azzurri P Bacchetta N Badgett W Barbaro-Galtieri A Barnes VE Barnett BA Baroiant S Bartsch V Bauer G Beauchemin PH Bedeschi F Behari S Bellettini G Bellinger J Belloni A Benjamin D Beretvas A Beringer J Berry T Bhatti A Binkley M Bisello D Bizjak I Blair RE Blocker C Blumenfeld B 《Physical review letters》2007,99(15):151801
We present a measurement of the W-boson mass using 200 pb{-1} of data collected in pp[over ] collisions at sqrt[s]=1.96 TeV by the CDF II detector at run II of the Fermilab Tevatron. With a sample of 63 964 W-->enu candidates and 51 128 W-->munu candidates, we measure M_{W}=80 413+/-34{stat}+/-34{syst}=80,413+/-48 MeV/c;{2}. This is the most precise single measurement of the W-boson mass to date. 相似文献
14.
Low-temperature heat capacities and standard molar enthalpy of formation of 4-(2-aminoethyl)-phenol (C8H11NO) 下载免费PDF全文
This paper reports that low-temperature heat capacities of 4-(2-aminoethyl)-phenol (C8H11NO) are measured by a precision automated adiabatic calorimeter over the temperature range from 78 to 400 K. A polynomial equation of heat capacities as a function of the temperature was fitted by the least square method. Based on the fitted polynomial, the smoothed heat capacities and thermodynamic functions of the compound relative to the standard reference temperature 298.15K were calculated and tabulated at the interval of 5K. The energy equivalent, εcalor, of the oxygen-bomb combustion calorimeter has been determined from 0.68g of NIST 39i benzoic acid to be εcalor=(14674.69±17.49)J·K^-1. The constant-volume energy of combustion of the compound at T=298.15 K was measured by a precision oxygen-bomb combustion calorimeter to be ΔcU=-(32374.25±12.93)J·g^-1. The standard molar enthalpy of combustion for the compound was calculated to be ΔcHm = -(4445.47 ± 1.77) kJ·mol^-1 according to the definition of enthalpy of combustion and other thermodynamic principles. Finally, the standard molar enthalpy of formation of the compound was derived to be ΔfHm(C8H11NO, s)=-(274.68 ±2.06) kJ·mol^-1, in accordance with Hess law. 相似文献
15.
Bi-ferroic particulate composites with Tb_{0.28}Dy_{0.72}Fe_2 (Terfenol-D) particles randomly dispersed in ferroelectric polyvinylidene fluoride matrix prepared by a simple hot-pressing procedure were investigated. With increasing concentration of Terfenol-D, the magnetic susceptibility, saturation magnetization and initial permeability of the composites increases. The dependence of the effective magnetostriction on applied bias for the composites is similar to that for bulk Terfenol-D, but the effective magnetostriction strongly depends on the volume fraction of Terfenol-D. The observed behaviour of the composite is reasonably described by using effective medium theories. 相似文献
16.
We have investigated the exchange bias and training effect in the
ferromagnetic/antiferromagnetic (FM/AF) heterostructures using a
unified Monte Carlo dynamical approach. The magnetization of the
uncompensated AF layer is still open after the first field cycling
is finished. Our simulated results show obvious shift of hysteresis
loops (exchange bias) and cycling dependence of exchange bias
(training effect) when the temperature is below 45~K. The exchange
bias field decreases with decreasing cooling rate or increasing
temperature and the number of the field cycling. Essentially, these
two effects can be explained on the basis of the microscopical
coexistence of both reversible and irreversible moment reversals of
the AF domains. Our simulations are useful to understand the real
magnetization dynamics of such magnetic heterostructures. 相似文献
17.
研究铁磁/反铁磁/铁磁三层膜中界面存在二次以及双二次交换耦合下反铁磁磁矩转动及其交换各向异性.结果表明,其反铁磁膜中的磁矩转动存在可逆"恢复行为"、不可逆"连续倒转行为"以及不可逆"中断倒转行为"三种情形,三种情形的出现强烈地依赖于两界面处的线性耦合和双二次耦合.钉扎界面的交换耦合与旋转界面的交换耦合相互竞争,当钉扎界面耦合占主导时,反铁磁磁矩发生可逆"恢复行为",系统出现交换偏置.在旋转界面耦合占主导情形下,其线性耦合与双二次耦合也相互竞争,分别导致反铁磁磁矩发生不可逆"连续倒转行为"和不可逆"中断倒转行为",系统都不出现交换偏置,但矫顽场都得以增强.相关结论为实验上观测的磁滞能耗以及界面垂直耦合提供了可能的解释. 相似文献
18.
Abouzaid E Arenton M Barker AR Bellantoni L Blucher E Bock GJ Cheu E Coleman R Corcoran MD Cox B Erwin AR Escobar CO Glazov A Golossanov A Gomes RA Gouffon P Hsiung YB Jensen DA Kessler R Kotera K Ledovskoy A McBride PL Monnier E Nelson KS Nguyen H Niclasen R Phillips DG Ping H Ramberg EJ Ray RE Ronquest M Santos E Slater W Smith D Solomey N Swallow EC Toale PA Tschirhart R Velissaris C Wah YW Wang J White HB Whitmore J Wilking MJ Winstein B Winston R Worcester ET Worcester M Yamanaka T 《Physical review letters》2007,99(8):081803
This Letter is the first report of the K{L}-->pi{+/-}e{-/+}nue{+}e{-} decay. Based on 19 208+/-144 events, we determine the branching fraction, B(K{L}-->pi{+/-}e{-/+}nue{+}e{-}M_{e{+}e{-}}>5 MeV/c{2},E{e{+}e{-}}{*}>30 MeV)=(1.285+/-0.041)x10{-5}, and Gamma(K{e3ee}M{e{+}e{-}}>5 MeV/c{2})/Gamma(K{e3})=[4.57+/-0.04(stat)+/-0.14(syst)]x10{-5}. This ratio agrees with a theoretical prediction based on chiral perturbation theory (ChPT) calculated to O(p{4}). The measured kinematical distributions agree with those predicted by just ChPT O(p{4}), but show significant disagreement with ones predicted by leading-order ChPT. 相似文献
19.
We have studied the nonequilibrium dynamic phase transitions of both three-dimensional (3D) kinetic Ising and Heisenberg spin systems in the presence of a perturbative magnetic field by Monte Carlo simulation. The feature of the phase transition is characterized by studying the distribution of the dynamical order parameter. In the case of anisotropic Ising spin system (ISS), the dynamic transition is discontinuous and continuous under low and high temperatures respectively, which indicates the existence of a tri-critical point (TCP) on the phase boundary separating low-temperature order phase and high-temperature disorder phase. The TCP shifts towards the higher temperature region with the decrease of frequency, i.e. T_{TCP}=1.33×exp(-ω/30.7). In the case of the isotropic Heisenberg spin system (HSS), however, the situation on dynamic phase transition of HSS is quite different from that of ISS in that no stable dynamical phase transition was observed in kinetic HSS after a threshold time. The evolution of magnetization in the HSS driven by a symmetrical external field after a certain duration always tends asymptotically to a disorder state no matter what an initial state the system starts with. The threshold time τ depends upon the amplitude H_{0}, reduced temperature T/T_C and the frequency ω as τ=C·ω^α·H_0^{-β}·(T/T_C)^{-γ}. 相似文献
20.
The Ni/4H-SiC Schottky barrier diodes (SBDs) and transfer length
method (TLM) test patterns of Ni/4H-SiC Ohmic contacts were
fabricated, and irradiated with 1~MeV electrons up to a dose of
3.43× 1014~e/cm-2. After radiation, the forward
currents of the SBDs at 2~V decreased by about 50%, and the
reverse currents at -200~V increased by less than 30%. Schottky
barrier height (φ B ) of the Ni/4H-SiC SBD increased
from 1.20~eV to 1.21~eV under 0~V irradiation bias, and decreased
from 1.25~eV to 1.19~eV under -30~V irradiation bias. The
degradation of φ B could be explained by the variation
of interface states of Schottky contacts. The on-state resistance
(Rs) and the reverse current increased with the dose, which
can be ascribed to the radiation defects in bulk material. The
specific contact resistance (\rhoc) of the Ni/SiC Ohmic
contact increased from 5.11× 105~Ωega.cm2 to 2.97× 10-4~Ωega.cm2. 相似文献