Temperature-electric field hysteresis loop of multicaloric effects in PbZr0.8Ti0.2O3 thin films

The Multicaloric effect in the PbZr_0.8Ti_0.2O₃ thin films is investigated with the application of sine wave electric field, dc electric field and stress using a phase field method combined with the thermodynamic analysis. The simulation results show that the adiabatic temperature change-electric field curve presents a shape of butterfly in the presence of the sine wave electric field. In order to detect the effect of the sine wave electric field, the multicaloric effect and the domain structures under the direct electric field and the sine wave electric field are compared. It is found that the domain switching behaviors are quite different under the different applied electric fields. And the negative multicaloric effect in the PbZr_0.8Ti_0.2O₃ thin film is attribute to the domain switching under the external field.     

Interface induced exchange bias effect in La0.67Sr0.33MnO3/SrIrO3 multilayer

Epitaxial superlattices of ferromagnetic/paramagnetic La_0.67Sr_0.33MnO₃/SrIrO₃ materials have been prepared on SrTiO₃ (100) substrate using pulse laser deposition technique. An unexpected onset of interface magnetic interaction has been observed around 40 K. Interestingly, magnetic exchange bias effect has been observed in both field cooled and zero field cooled magnetization loops, however, the shifting of loop is opposite in both measurements. Exchange bias field vanishes as temperature increases to interface magnetic ordering temperature. Moreover, exchange bias field is found to decrease with increasing cooling field. We believe that tuning of magnetic exchange at interface during field cooling induces this evolution in nature of exchange bias field.     

Stimulated emission and multi-peaked absorption in a four level N-type atom

Absorption and refraction of the inner transition F₂\leftrightarrow F₃ of the closed four level N-type atom have been investigated under a weak field. The outer transitions F₁\leftrightarrow F₃ and F₂\leftrightarrow F₄ are resonantly interacted with drive field with frequency \omega_c and Rabi frequency \Omega_c, and saturation field with \Omega_s and \Omega_s, respectively. For the suitable Rabi frequencies \Omega_c and \Omega_s, we obtain the Mollow absorption spectrum of probe field. The reason is that the drive field excites the atom to the upper level F_c and simultaneously the saturation field takes the atom out of the lower level F₂, leading to the stimulated emission. Meanwhile, due to the dynamic energy splitting induced by the drive and saturation fields, the two- and four-peaked absorption spectra are observed. At the zero off-resonance detuning of probe field, we also find the transfer of dispersion from negative to positive with an increment of \Omega_s. Finally, the refractive index enhancement is predicted for a wide spectral region.     

磁场对液态铝和固态铁界面微观组织的影响

研究了直流磁场、交流磁场对液态铝和固态铁界面微观组织的影响，采用金相显微镜、电子探针和x射线衍射等方法对其扩散层内生成物进行了分析.结果表明，在直流磁场和交流磁场作用下，固态铁界面内形成的扩散层厚度均比无磁场时小；在交流磁场作用下，液态铝和固态铁的界面变得凹凸不平；在垂直于磁场方向上，直流磁场抑制了铝原子和铁原子之间的扩散，交流磁场则促进了扩散；无磁场时固态铁内扩散层中生成的金属间化合物由FeAl₃和Fe₂Al₅组成，直流磁场条件下只有Fe₂Al_{5生成，交流磁场作用下由Fe2Al5和Fe4Al13组成. 关键词： 磁场 铝 铁 金属间化合物 扩散}     

在Tokamak装置中用中空超导环段冻结环向磁场的设想

本文提出一个设想:即将n个中空超导圆柱体放置于n饼纵场线圈之中,分段冻结环向磁场,则其所需要的电功率将比常规线圈降低到2/n倍。我们知道超导材料的冻结场可近似地写为。H_fj(r,T)=H_fj(r,0)[1-(T/(T_c))²。因此选定T=T₁,当轴向场H在大圆环的内壁达到H≥H_fj(r,T₁)时,中空体的内边缘达到临界场,则场进入中空区,再使H降到零,中     

Stability of the director profile of a nematic liquid crystal around a spherical particle under an external field

We study numerically the effect of an external magnetic or electric field on the director profiles of a nematic liquid crystal around a spherical particle. We pay particular attention to the stability of a hyperbolic hedgehog defect accompanying the particle, which transforms into a Saturn-ring defect encircling the particle under a sufficiently strong external field. We focus on the particle size dependence of the two important threshold field strengths: the “thermodynamic-transition” field strength H₁ at which the hedgehog and the Saturn-ring configurations have the equal free energy, and the critical field strength H₂ at which the hedgehog loses its (meta)stability. Our numerical results demonstrate that while H₁ is non-monotonically dependent on the particle radius R₀, H₂ monotonically increases with R₀ and the dependence of H₂ is weak for large R₀. The non-monotonic dependence of H₁ on R₀ can be explained by comparing the energies of the two configurations and assuming the dependence of those energies on a rescaled field. A crude argument of the energetics of a hyperbolic hedgehog defect under an external field shows that for an asymptotically large R₀ the critical field strength is independent of R₀, which agrees with our numerical finding.     

Force field calculations of acetonitrile using CNDO/force method

The redundancy-free internal valence force field (RFIVFF) of acetonitrile is reported using CNDO/force method. The initial force field is set up by taking the interaction and bending force constants from CNDO force field and transferring stretching force constants from the force fields of chemically related molecules. The final force field is obtained by refining the initial force field using vibrational harmonic frequencies of CH₃CN,¹³CH₃CN, CH₃ ¹³CN, CH₃C¹⁵N, CD₃CN and CD₃ ¹³CN. The final force field thus obtained is found to be excellent on the basis of frequency fit and potential energy distribution.     

Magnetoelectric coupling in antiferroelectric and magnetic laminate composites

We researched the properties of magnetoelectric composites between antiferroelectric Pb_0.94La_0.04(Zr_0.55Sn_0.3Ti_0.15)O₃ and magnetic Terfenol-D. The magnetic field enhances the electric field-induced strain and polarization of the composite. The magnetic moment induced by the electric field increases at the electromechanical resonance frequency because the antiferroelectric ceramics exhibit ferroelectric behaviors under a high electric field. The induced magnetic moment increases with decreasing thickness ratio and shows a hysteresis loop with the bias magnetic field. Due to the antiferroelectric characteristics, it also shows a hysteresis loop with the bias electric field, which could be used in the magnetic switch controlled by electricity.     

SrCl2:Co++EPR谱电场效应的理论解释

本文从理论上研究了[111]方向电场对SrCl₂:Co⁺⁺的EPR谱的影响。结果表明:外电场使晶格发生畸变而偏离原来的O_h对称,成为C_3v。由此圆满地从理论上解释了零场分裂因子D随电场强度E线性变化的实验规律,并从理论上预言了晶格在平行电场方向的变化率为α=—8×10^-5α₀mm/kV,在垂直电场方向的变化率β=1.66×10^-4α₀关键词：     

Magnetic properties of lithographically defined lateral Co/Ni80Fe20 wires

A novel micro-fabrication technique has been used to create an array of lateral magnetic multilayers consisting of micron-sized sputtered Co and Ni₈₀Fe₂₀ wires. The structures were fabricated using conventional optical lithography and a combination of hard and soft lift-off methods. For the field applied parallel to the wires intrinsic easy axis, we observed two switching fields corresponding to the distinct coercive field of the Ni₈₀Fe₂₀ wires (H_c1) and Co wires (H_c2) constituting the lateral multilayer wire array. A state of anti-parallel relative alignment of magnetization was observed when the applied field is greater than the switching field of Ni₈₀Fe₂₀ wires but less than the switching field of Co wires. We found the region of anti-parallel alignment of magnetization between the Co and Ni₈₀Fe₂₀ wires to be very sensitive to the relative orientation of the applied magnetic field.     

Effect of electromagnetic field strength on Ni0.35Zn0.65Fe2O4 as performed by combustion synthesis

Ni_0.35Zn_0.65Fe₂O₄ ferrite is prepared through combustion synthesis in the external electromagnetic field. The highest magnetic field strength for the experiment is 1.1 T. Reactions temperatures were monitored by infrared radiation thermometer, the synthesized ferrite prepared in different magnetic fields is analyzed by XRD, SEM, and VSM. The results indicate that the coercivity of ferrite gradually decrease with the increase of magnetization. When the magnetic field strength is 0.54 T, the saturation magnetization is improved up to 56.05 emu/g (42%) as compared to that of ferrite in zero magnetic field. Through SEM analysis of Ni_0.35Zn_0.65Fe₂O₄ ferrite, homogeneous grains of the crystal are observed. With the increase of external magnetic field, the ferrite grain improved. This paper also systematically explores the effect of the electromagnetic field on ferrite by combustion synthesis.     

Specific heat of Sm0.55Sr0.45MnO3 manganite in magnetic fields up to 15 T: An anomalous critical behavior of the ferromagnet in magnetic field and the observation of a tricritical point

The specific heat of Sm_0.55Sr_0.45MnO₃ manganite is measured in the vicinity of the ferromagnetic phase transition in strong magnetic fields up to 15 T. An anomalous critical behavior of the Sm_0.55Sr_0.45MnO₃ ferromagnet in magnetic field is predicted and experimentally observed. The anomalous behavior manifests itself in that, in magnetic fields up to 4 T, the field favors fluctuations and the specific-heat anomaly increases with the field and sharpens, becoming λ-shaped. In fields above 4 T, the behavior becomes classical: the field suppresses the fluctuations and the specific-heat peak is smeared out. The hysteresis of the transition temperature measured in the heating and cooling runs is about 15 K in zero magnetic field. As the field increases, it narrows gradually and vanishes completely when the field reaches 4 T. The results of the experiments are explained in terms of the competition between the hysteresis and the fluctuations of the magnetic order parameter. The H-T phase diagram of Sm_0.55Sr_0.45MnO₃ certainly indicates that, at 4 T, Sm_0.55Sr_0.45MnO₃ has a tricritical point, at which the ferromagnetic and paramagnetic phases of Sm_0.55Sr_0.45MnO₃ are leveled.     

Formation of N3+ in pulsed-laser stimulated field desorption of nitrogen from metal surfaces

In pulsed-laser stimulated field desorption of nitrogen from metal surfaces, a plenty of N₃⁺ can be detected. Here we present the result of a study of the field dependence and emitter material specificity of N₃⁺ formation in pulsed-laser stimulated field desorption. These ions are formed by field ionization of N₃ molecules which are thermally desorbed from their field adsorption states by laser pulse heating of the surface.     

Temperature and magnetic field dependences of the London penetration depth and coherence length in the vortex state of YBa2Cu3O7-\delta

We report TF‐μ⁺SR measurements of the London penetration depth in the high‐T_c superconductor YBa₂Cu₃O_7-\delta as a function of temperature T and magnetic field H. The magnetic field distribution in high quality single crystals of YBa₂Cu₃O_6.95 was fit assuming a triangular vortex lattice with an average in‐plane penetration depth \lambda_ab=1155(3) Å, extrapolated to zero temperature and magnetic field. We find that \lambda_ab(T,H) increases linearly both as a function of magnetic field and temperature in the field range studied. This unusual behaviour is attributed to an unconventional pairing scheme in which there are line nodes in the superconducting energy gap function. Measurements have also been made on a deoxygenated sample, YBa_2Cu_3O_6.60. The lineshapes for YBa₂Cu₃O_6.60 clearly show the high‐field cutoff due to the finite coherence length \xi_ab. A preliminary analysis indicates that \xi_ab(T,H) increases linearly as a function of temperature and decreases with increasing magnetic field.     

Electronic structure of paramagnetic In<Subscript>1-x</Subscript>Mn<Subscript>x</Subscript> As nanowires

The electronic structure, spin splitting energies, and g factors of paramagnetic In_1-xMn_xAs nanowires under magnetic and electric fields are investigated theoretically including the sp-d exchange interaction between the carriers and the magnetic ion. We find that the effective g factor changes dramatically with the magnetic field. The spin splitting due to the sp-d exchange interaction counteracts the Zeeman spin splitting. The effective g factor can be tuned to zero by the external magnetic field. There is also spin splitting under an electric field due to the Rashba spin-orbit coupling which is a relativistic effect. The spin-degenerated bands split at nonzero k_z (k_z is the wave vector in the wire direction), and the spin-splitting bands cross at k_z = 0, whose k_z-positive part and negative part are symmetrical. A proper magnetic field makes the k_z-positive part and negative part of the bands asymmetrical, and the bands cross at nonzero k_z. In the absence of magnetic field, the electron Rashba coefficient increases almost linearly with the electric field, while the hole Rashba coefficient increases at first and then decreases as the electric field increases. The hole Rashba coefficient can be tuned to zero by the electric field.     

Characteristics of SrBi2Ta2O9 ferroelectric films in an in situ applied low electric field prepared by metalorganic decomposition

SrBi₂Ta₂O₉ (SBT) films were prepared on Pt/TiO₂/SiO₂/Si substrates at 750 °C in oxygen by metalorganic decomposition method. A low electric field was in situ applied during the film crystallization. It was first found that a low electric field and its direction have significant influence on the microstructures and ferroelectric properties of SBT films. Under a positive electric field (assuming that the bottom electrode is electrically grounded), the films show stronger c-axis-preferred orientation than without electric field and under a negative electric field. As a possible origin is proposed that the interface-induced nucleation growth between SBT and Pt coated substrate with application of low electric field plays a key role. Above all, an in situ applied low electric field during the film crystallization is a promising technique controlling film orientation for film preparation by wet chemical method.     

Magnetic irreversibility and metastability in a CuMn alloy

Our magnetic measurements on a CuMn alloy reveal that T_m, the temperature of the susceptibility peak, is marked by a qualitative change in the magnetization-vs.-field behavior. The magnetization process at and above T_m is reversible at all fields, whereas below T_m an irreversibility sets in at a threshold field H₁ and persists up to a second threshold field H₂. The irreversibility results in an isothermal remanence whose saturation value (attained when the field removed exceeds H₂) equals the saturation value of the thermoremanence (attained after cooling from above T_m in a field larger than H₂). Both states of remenence are characterized by a magnetization which is completely reversed by a small reverse field but returns to its original polarity when the field is removed. The hysteresis loop remains thus displaced as long as the cycling field is less than H₁.     

Electric field effects on the dielectric and acoustic anomalies of Pb[(Mg1/3Nb2/3)0.83Ti0.17]O3 single crystals studied by dielectric and Brillouin spectroscopies

The effect of the electric field on the dielectric and acoustic properties of Pb[(Mg_1/3Nb_2/3)_0.83Ti_0.17]O₃ single crystals was investigated as functions of temperature and the electric field strength. The dielectric constant and the acoustic mode behaviors exhibited typical relaxor behaviors when there was no bias field. The longitudinal acoustic mode showed splitting under a moderate electric field of 1 kV/cm applied along the [001] direction, indicating coexistence of macroscopic/mesoscopic ferroelectric states and relaxor states. Further increase in the electric field up to 2 kV/cm induced a clear ferroelectric phase transition, which became smeared out due to the proximity of the electric field to the critical point. The electric field-temperature phase diagram of Pb[(Mg_1/3Nb_2/3)_0.83Ti_0.17]O₃ was suggested based on the observed field-induced changes in the dielectric and the acoustic properties.     

Magnetoimpedance effect in FeCoMoSiB amorphous sheets

The magnetoimpedance effect in sheets made of Fe₄Co₆₇Mo_1.5Si_16.5B₁₁ amorphous metallic alloy is studied in relation to the mutual orientations of the sheet axis, permanent magnetic field, and variable electrical current. Also, the effective permeability is studied as a function of the mutual orientations of the sheet axis, permanent magnetic field, and rf magnetic field. Under certain orientations of the rf magnetic field and rf electrical current relative to the sheet axis, experimental dependences of the magnetoimpedance effect and effective permeability on the permanent magnetic field are found to correlate qualitatively. The experimental data are explained in terms of domain reconfiguration in the alloys.     

两原子与双模腔场喇曼相互作用(g1≠g2)的辐射谱

研究了两个有效双能级原子与双模腔场具有不同耦合常数(g₁≠g₂)时通过喇曼相互作用的辐射谱,详细讨论了双模腔场分别处于不同数态时的情形,发现其辐射谱具有如下新特点:当模1腔场处于真空态,模2腔场处于弱场中时,随着R=g₂/g₁的增加,辐射谱交替出现对称的10峰、6峰结构,与单模双原子情形相比较,更为灵敏地反映出两原子与腔场间不同的喇曼相互作用强度;当模1腔场处于真空态、模2腔场处于强场中时,0相似文献