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Magnetic and thermodynamic properties of polycrystalline multiferroic Bi 0.65 La 0.35 Fe 0.5 Sc 0.5 O 3 synthesized under high-pressure and high-temperature conditions are reported. Magnetic properties were studied using a SQUID magnetometer technique over the temperature range of 5−300 K in magnetic fields up to H =10 kOe. The field dependent magnetization M(H) was measured in magnetic fields up to 50 kOe at different temperatures up to 230 K after zero-field cooling procedure. A long-range magnetic ordering of the AFM type with a weak FM contribution occurs below the Neel temperature T N ~237 K. Magnetic hysteresis loops taken below T N show a huge coercive field up to H c ~10 kOe. A strong effect of magnetic field on the magnetic properties of the compound has been found. Derivative of the initial magnetization curves demonstrates a temperature-dependent anomaly in fields of H =15−25 kOe. Besides, an anomaly of the temperature dependent zero-field cooled magnetization measured in magnetic fields of 6−7 kOe has been found. Origin of both anomalies is associated with inhomogeneous magnetic state of the compound. The heat capacity has been measured from 2 K up to room temperature and a significant contribution from the magnon excitations at low temperatures has been detected. From the low-temperature heat capacity, an anisotropy gap of the magnon modes of the order 3.7 meV and Debye temperature T D =189 K have been determined.

The temperature dependence of the ac magnetic susceptibility of a single-crystal mixed rare-earth garnet Er2HoAl5O12 has been investigated within the range from 1.8 to 300 K in a zero constant field and in applied bias fields of up to 9 T. In the absence of a constant magnetic field the magnetic susceptibility followed the Curie–Weiss law. The application of a constant magnetic field caused a magnetic phase transition, the temperature of which increased with increasing magnetic field. The temperature of the maximum of the ac magnetic susceptibility, which is a characteristic of the phase transition, did not show a noticeable dependence on the frequency of the alternating magnetic field.

First order antiferromagnetic to ferromagnetic transition and path dependent magnetic states in La 1− x Nd x Fe 11.5 Al 1.5 for x ∼0.1 are studied at low temperatures via powder x-ray diffraction, magnetization, and specific heat measurements. X-ray diffraction measurements suggest that around 8% of high temperature antiferromagnetic phase is converted to ferromagnetic phase at low temperatures in zero field cooling. A systematic study of temperature and magnetic field dependent magnetization measurements show a non-monotonic variation of upper critical field and re-entrant antiferromagnetic-ferromagnetic-antiferromagnetic transition while warming at an applied magnetic field under zero-field-cooled condition. This has been interpreted in the framework of kinetic arrest model for first order magnetic transition. It is also found that the antiferromagnetic phase is in the non-equilibrium state and behaves as a glass-like magnetic state at low temperatures. The specific heat in field-temperature space is studied and found to have a lower electronic contribution for the non-equilibrium antiferromagnetic state, compared to the equilibrium ferromagnetic state in this compound.

The magnetic properties of an unexpected superconducting bilayer consisting of non-superconducting Bi and ferromagnetic Ni have been investigated. A large magnetization signal is observed when the sample is cooled below the superconducting transition temperature in zero magnetic field, which has the same direction with the magnetization of the adjacent Ni layer. Interestingly, this Bi/Ni bilayer shows opposite responses to external magnetic field in zero field cooling (ZFC) process and field cooling (FC) process. It behaves diamagnetically in ZFC while paramagnetically in FC. Besides, magnetic hysteresis loops below the superconducting transition temperature show flux pinning and flux jumping effects.

The paper considers the results of measuring the elastic parameters (ponderomotive elasticity coefficient, oscillation frequency, attenuation coefficient) of the oscillatory system with an inertial element that is a magnetic fluid column retained in a tube due to magnetic levitation in a strong magnetic field. Elasticity is provided by the ponderomotive force which affects the upper and lower thin layers of the fluid column. Measurement results of vibration parameters of the oscillatory system can be useful for the investigations of magnetophoresis and aggregation of nanoparticles in magnetic fluids.

Materials which are close to a quantum critical point are rather prone to magnetic instabilities; even small modifications of relevant interaction mechanisms can be responsible for a magnetic phase transition to occur at finite temperatures. In this work it is demonstrated that actually a substitution of Ce by non-magnetic La in Ce3Pd4Si4 drives a magnetic instability, with ordering temperatures as high as 10 K. To trace the evolution of magnetism and the onset of long range magnetic order in Ce3-xLaxPd4Si4, various bulk property measurements were carried out.

We have studied the functional behavior of the field-cooled (FC) magnetic relaxation observed in melt-textured YBa2Cu3O7-δ (Y123) samples with 30 wt% of Y2Ba1Cu1O5 (Y211) phase, in order to investigate anomalous paramagnetic moments observed during the experiments. FC magnetic relaxation experiments were performed under controlled conditions, such as cooling rate and temperature. Magnetic fields up to 5T were applied parallel to the ab plane and along the c-axis. Our results are associated with the paramagnetic Meissner effect (PME), characterized by positive moments during FC experiments, and related to the magnetic flux compression into the samples. After different attempts our experimental data could be adequately fitted by an exponential decay function with different relaxation times. We discuss our results suggesting the existence of different and preferential flux dynamics governing the anomalous FC paramagnetic relaxation in different time intervals. This work is one of the first attempts to interpret this controversial effect in a simple analysis of the pinning mechanisms and flux dynamics acting during the time evolution of the magnetic moment. However, the results may be useful to develop models to explain this interesting and still misunderstood feature of the paramagnetic Meissner effect.

The magnetic relaxation of MgB 2 thin film deposited on Al 2 O 3 substrate by hybrid physical-chemical vapor deposition method was investigated. The rate of magnetic relaxation (the logarithmic decay rate) S, which was obtained by the time dependence of magnetic moment m(t) at fixed magnetic field H and temperature T, of the MgB 2 thin film was investigated. The decay of magnetic moment m(t) was carried out at temperatures between 5 and 37.5 K in the field ranges of 0.1-1.0 T, using PPMS-VSM (Quantum Design). The decrease of magnetic moment m(t) for 7200 s at T = 5 K was about 2%-3% and 0.2%-0.3% when the field was applied parallel to the c-axis and the ab-plane, respectively. The logarithmic decay rate S in the field parallel to the ab-plane was much smaller than that parallel to the c-axis over all temperature ranges. The time-independent behavior of logarithmic decay rate S at low temperatures below T = 10 K implies the presence of quantum creep effect.

The magnetic properties and magnetic entropy changes of DyCo 2 B x ( x =0, 0.05, 0.1, and 0.2) alloys were investigated. The Curie temperature ( T C ) increases with increasing B concentration. The frequency dependence of ac magnetic susceptibility of DyCo 2 caused by the narrow domain wall pinning effect is depressed by B doping, but the coercivity and the magnetic viscosity are prominently increased in the B doped alloys. The magnetic transition nature of DyCo 2 B x changes from the first-order to the second-order with increasing x , which leads to the decrease of the maximum magnetic entropy change. However, the relative cooling power (RCP) of DyCo 2 and the B doped alloys remains nearly constant.

The results of experimental studies of magnetic flux dynamics in finite-size superconductors, obtained using integral and local measurements methods, are presented. Local methods were aimed at clarifying the role of the demagnetizing factor in the dynamic formation of a complex magnetic structure of the critical state of hard superconductors. To understand the reasons for drastic transformation of the magnetic induction, we further analyzed the literature data on the visualization of flux dynamics in the presence of avalanches, obtained by magneto-optical methods. New features in the behavior of the magnetic flux during and after an avalanche were revealed and characterized: two stages in the formation of the magnetic induction distribution inside the avalanche region were established—homogeneous and heterogeneous filling with magnetic flux; the mechanism of inversion of the induction profile; velocity oscillations in the propagating magnetic flux front; transformation of the critical state band near the ...

A new variational method has been proposed for studying the equilibrium states of the interacting particle system to have been statistically described by using the density matrix. This method is used for describing conductivity electrons and their behavior in metals. The electron energy has been expressed by means of the density matrix. The interaction energy of two ekk′ electrons dependent on their wave vectors k and k’ has been found. Energy ekk′ has two summands. The first energy I summand depends on the wave vectors to be equal in magnitude and opposite in direction. This summand describes the repulsion between electrons. Another energy J summand describes the attraction between the electrons of equal wave vectors. Thus, the equation of wavevector electron distribution function has been obtained by using the variational method. Particular solutions of the equations have been found. It has been demonstrated that the electron distribution function exhibits some previously unknown features at low temperatures. Repulsion of the wave vectors k and –k electrons results in anisotropy of the distribution function. This matter points to the electron superconductivity. Those electrons to have equal wave vectors are attracted thus producing pairs and creating an energy gap. It is considered the influence of magnetic field on the superconductor. This explains the phenomenon of Meissner and Ochsenfeld. We consider a new possibility of penetration of the external magnetic field into the superconductor.

Magnetic, dielectric and magnetoelectric properties of the polycrystalline Co4NbTaO9 have been investigated in this paper. The antiferromagnetic phase transition of this compound is identified at the temperature of 23.6 K. Anomalies in the temperature-dependent dielectric constants and pyroelectric currents emerge around its magnetic transition point under magnetic field, and increase with the increasing external magnetic field. Antiferromagnetic fluctuation and domain effect are considered to be response for the phenomenon observed in this compound.

Hereby it studied the fundamental theory created by the London brothers for interpretation of the magnetic field reduction in superconductors. As demonstrated, this theory is not correct. The author of this work has developed the new theory of superconductivity. The equation describing the electron distribution function under the effect of magnetic field explains existence of the Meissner-Ochsenfeld effect. It is shown that the critical field equation matches the width of a potential well in the kinetic energy dependence of mean electron energy. As a result, the supercurrent density formula has been derived. Existence of magnetic fields is explained by two steady-state Maxwell equations. There are magnetic fields that are found to be created in individually shaped metals. Penetration of the external magnetic field in a superconductor has been explained.

A biomagnetic-electrical model is presented that explains rather well the experimentally observed synchronization of the bioelectric potential firing rate (“frequency”), f , of single unit neurons of Helix aspersa mollusc under the application of extremely low frequency (ELF) weak alternating (AC) magnetic fields (MF). The proposed model incorporates to our widely experimentally tested model of superdiamagnetism (SD) and Ca 2+ Coulomb explosion (CE) from lipid (LP) bilayer membrane (SD–CE model), the electrical quadrupolar long range interaction between the bilayer LP membranes of synchronized neuron pairs, not considered before. The quadrupolar interaction is capable of explaining well the observed synchronization. Actual extension of our SD–CE-model shows that the neuron firing frequency field, B , dependence becomes not modified, but the bioelectric frequency is decreased and its spontaneous temperature, T , dependence is modified. A comparison of the model with synchronization experimental results of pair of neurons under weak ( B 0 ≅ 0.2–15 mT) AC-MF of frequency f M =50 Hz is reported. From the deduced size of synchronized LP clusters under B , is suggested the formation of small neuron networks via the membrane lipid correlation.

In strong magnetic field the longitudinal magnetoconductivity in 3D chiral materials is shown to exhibit a new type of quantum oscillations arising from the chiral magnetic effect (CME). These quantum CME oscillations are predicted to dominate over the Shubnikov-de Haas (SdH) ones in chiral materials with an approximately conserved chirality of quasiparticles at strong magnetic fields. The phase of quantum CME oscillations differs from the phase of the conventional SdH oscillations by $\pi/2$., Comment: 5 pages, 3 figures

The evolution of flux distribution in MgB2 single crystals during their remagnetization was imaged with magneto-optical technique. Meissner holes, formed as the areas where the annihilation of vortices and antivortices takes place, were found at the boundary between oppositely magnetized parts of the crystal. Gradient of magnetic induction in the vicinity of Meissner holes was found to be enhanced. Finger-like structures of convex shape, formed during the penetration of magnetic flux inside the crystal, were observed and explained as an effect of inhomogeneous pinning and demagnetizing field redistribution in the sample.

The magnetic field distributions of an HTS bulk magnet system were precisely measured between the face-to-face 3.4-T magnetic poles. After the activation by 5-T field cooling magnetization, the magnetic flux density has reached the value of 2.26 T at the center of the 34-mm gap. The sum of the local magnetic fields generated from each magnetic pole coincides with the local field strength in the gap. We estimated the homogeneity of the magnetic flux densities of Bz and By, which were measured at various positions along z and y-axes in the center portion of the 60-mm gap. Since the magnetic flux density becomes smooth with increasing distance, we obtained the smallest distribution range of 123 ppm of Bz = 1.62 T at the center of the gap as for Bz. On the other, as for By, the smallest distribution range of 1125 ppm of Bz = 1.20 T was obtained at z = 1.7 mm distant from the center point. Since there must exist a certain plane which has no vector components along the radius direction at the center of the gap, the closer the z-positions come to the null point, the more homogeneous the field distribution becomes.

The results of magneto-optical investigations of the magnetization processes in high-temperature superconducting coated conductor composites are presented. The studies were performed in the temperature range of 4–80 K. It is shown that the re-magnetization of composites in external magnetic field is accompanied by formation and propagation of the magnetic flux annihilation waves (areas with zero magnetic induction). The relationship between penetration depth of annihilation front and the value of external magnetic field at different temperatures as well as temperature dependence of the rate of magnetic flux annihilation front motion are found. The experimental data agree qualitatively with the results of numerical calculations performed by using the Monte Carlo method.

Based on the dipole-dipole model and the critical state model, we derived analytical expressions for the levitation force between the magnetic tip and the finite superconducting cylinder in two states: the Meissner state and the critical state. The effect of the geometrical parameters of the levitating system on the force was investigated.

The most prominent macroscopic quantum mechanical effects in superconductivity are beside the zero electrical resistance the Meissner effect (magnetic field expulsion) and magnetic flux trapping (pinning) in materials in their superconducting state. Their i vestigations are still subject of many publications because of the lack of consistent models or a theory which describes flux domains or flux trapping in e.g. type-I superconductors. The spin of the neutron interacts with magnetic fields which can be visualized by radiography (and tomography) using polarized neutrons. It could be shown that both the Meissner effect and flux trapping in high purity lead samples (type-I super-conductor) occur different for the crystalline and polycrystalline samples, respectively. The trapped flux of an uni- form external magnetic field applied to the lead samples is for T < Tc not uniform distributed but centred and squeezed around the rod axis of the samples. Calculations c ncerning magnetic flux trapping agree perfectly with experimental images if a Gaussian shaped B-field is assumed. Disc-shaped different surface treated niobium samples (type-II superconductor) behave different con erning Meissner phase and intermediate state. Both seem to suppress nearly completely but different the Meissner state causing different flux trapping in the sample in the intermediate state. These macroscopic Quantum mechanical effects could be visualized by radiographies with polarized neutrons yielding a deep look at phase transition in superconductivity and based on them trapped fields could be calculated and quantified.

In a magnetic field, superconductivity is manifested by total magnetic field expulsion (Meissner effect) or by the penetration of integer multiples of the flux quantum {\Phi}_0. Here we present experimental results revealing magnetic dipoles formed by Meissner current flowing around artificially introduced topological defects (lattice of antidots). By using scanning Hall probe microscopy, we have detected ordered magnetic dipole lattice generated at spatially periodic antidots in a Pb superconducting film. While the conventional homogeneous Meissner state breaks down, the total magnetic flux of the magnetic dipoles remains quantized and is equal to zero. The observed magnetic dipoles strongly depend on the intensity and direction of the locally flowing Meissner current, making the magnetic dipoles an effective way to monitor the local supercurrent. We have also investigated the first step of the vortex depinning process, where, due to the generation of magnetic dipoles, the pinned Abrikosov vortices are deformed and shifted from their original pinning sites., Comment: 5 pages, 4 figures

The temperature and field dependences of the specific magnetic moment of the anion-deficient La0.70Sr0.30MnO2.85 manganite have been measured. It is established, that the magnetic state of the sample studied is a cluster spin glass and it is the result of frustration of exchange Mn3+-O-Mn3+ interactions due to the redistribution of oxygen vacancies. The increase of the magnetic field leads to an increase in the degree of polarization of local spins of manganese. It is established using the magnetic criterion that a phase transition into the paramagnetic state for the anion-deficient La0.70Sr0.30MnO2.85 manganite is a thermodynamic second order phase transition. The causes and mechanism of the magnetic phase separation are discussed.

The temperature dependence of the specific magnetic moment of anion-deficient manganite La0.70Sr0.30MnO2.85 is measured in external magnetic fields of 0–140 kOe, with the prehistory taken into account. The inhomogeneous magnetic state is a cluster spin glass and is the result of a redistribution of oxygen vacancies. Increasing the external magnetic field initially (H

We have studied the effect of high pressures on the electrical and magnetic properties of dilute magnetic semiconductor Cd0.82Mn0.18GeAs2. Electrical resistivity, Hall coefficient, transverse and longitudinal magnetic resistance, and magnetic susceptibility have been measured under high pressures (up to 9 GPa). The energy of a manganese impurity level was estimated at 155 meV from electrical resistivity and Hall factor versus temperature curves at the atmospheric pressure. Structural and magnetic phase transitions have been discovered in Hall resistance versus magnetic field curves measured at various temperatures; abnormal and normal Hall factors have been calculated.

Magnetic flux trapping and the homogeneity of the flux pinning are essential problems in the practical application of high-temperature superconductors. We have conducted study on the role of addition of soft magnetic Fe-B alloy particles contribute to the enhancement of the critical current density ( J c ) under wide-range of magnetic field. Magnetic flux trapping was enhanced in Gd123 bulk superconductor with suitable amount of magnetic particles addition. In addition, it can be effective as pinning center enhance the J c of the bulk in both the a – b growth sector and the c- growth sector under magnetic field. However, the T c of the Gd123 bulk was decreased obviously by addition of magnetic particles. The study on the spatial variation of superconducting properties indicates that the performance of the upper part of the bulk is better than the bottom. By comparing the superconducting properties of the Gd123 bulk with magnetic particles addition and without magnetic particles addition, we concluded that there is a trace of the formation of homogeneous pinning properties in the magnetic particles addition Gd123 bulk.

The notion of persistent current comes back to orbital currents in normal metals, semiconductors and even insulators displaying diamagnetic behavior in weak magnetic fields, but came to focus at the discovery of current persistence and magnetic flux quantization at large fields in atomically big but macroscopically small (mesoscopic) objects. The phenomenon bears much similarity with supercurrents in superconductive metals. We will review progress in developing of our understanding of the physical and technological aspects of this phenomenon. The exact solution for currents, magnetic moments and magnetomotive forces (torques) in crossed magnetic fields are presented. Time-dependent phenomena in crossed magnetic and electric fields, and in possibility of spontaneous persistent currents and of work extraction from static and dynamic quantum states are discussed.

In this work, we theoretically and experimentally established the common feature of the evolution of the efficiency of the electromagnetic generation of acoustic waves near the temperatures of second-order magnetic phase transitions characteristic of both the “order-disorder” (Curie point in isotropic ferromagnets) and “order-order” (easy-axis-angular-phase and angular-phase-easy-plane) transitions in uniaxial magnets, which consists in the fact that the peak of efficiency corresponds precisely to these temperatures at any values of the magnetic field even if in a magnetic field these temperatures cease to be the points of phase transitions.

The thermodynamic properties of a Bose gas of particles with nonzero spin and magnetic moment in states with and without a Bose-Einstein condensate are studied as a function of the external magnetic field. It is shown that there exists a temperature interval where a transition into a state with a Bose-Einstein condensate occurs in a Bose gas with constant temperature and particle number density when the magnetic field is increasing and reaches a critical magnitude. The temperature and magnetic field derivatives of the specific heat at constant volume and the magnetic susceptibility undergo a jump at such a transition.

We discuss the transport properties of a superconducting film under the influence of a tesla range spatially alternating magnetic field created by magnetic nanostructures placed outside a superconducting film with an insulating barrier between both so that they interact only via the magnetic field. A simple model for pinning by the spatially periodic magnetic field from the magnetic nanostructure qualitatively describes the data.

Longitudinal ultrasound attenuation of superfluid 3He in 98% aerogel has been measured at 33 bar and 6.22 MHz in the presence of magnetic fields up to 4.44 kG. The A-like to B-like (A-B like) phase transition in aerogel was identified by a rounded jump in attenuation while sweeping the temperature at a fixed magnetic field perpendicular to the direction of sound propagation. The suppression of the B-like phase was monitored as the magnetic field increased until the A-like phase region extended below our lowest attainable temperature (0.2 mK) at the highest field. In addition, the attenuation in the metastable A-like phase that appears when cooling in zero magnetic field was almost identical to the values observed in the A-like phase in high magnetic field.

The magnetic superconductor RuSr2Gd1.4Ce0.6Cu2O10-δ was studied by means of detailed magnetization measurements in order to clarify its complex magnetic and superconducting properties. Our experiments agree with a model indicating that the in-plane component of the Ru moment might transform from a spin-glass ground state to a ferromagnetically coupled excited state by application of a small magnetic field below the magnetic transition temperature. The experiments also show that a full Meissner state is present at the low temperature, the low magnetic field region of the phase diagram. This is in contrast to the previous prediction that no Meissner state exists in this material for an internal magnetic field of several hundred Oersteds in the CuO2 planes exerted by the Ru sublattice and exceeding the lower critical field.

A detailed study of magnetic properties of cobaltite YBaCo 2 O 5.5 has been performed in high (up to 35 T) magnetic fields and under hydrostatic pressure up to 0.8 GPa. The temperatures of paramagnet–ferromagnet (PM–FM) and ferromagnet–antiferromagnet (FM–AF) phase transitions and their pressure derivatives have been determined. It has been revealed that in the compound with yttrium, in contrast to those with magnetic rare earth atoms, the AF–FM field-induced magnetic phase transition is accompanied by a considerable field hysteresis below 240 K, and the magnetic field of 35 T is not sufficient to complete this transition at low temperatures. The hysteresis value depends on the magnetic field sweep rate, which considered as an evidence of magnetic viscosity that is especially strong in the region of coexistence of the FM and AF phases. High values of susceptibility for the field-induced FM phase show that Co spin state in these compounds changes in strong magnetic field.

Measurements of the complex permeability of the granular textured YBa2Cu3O7−δ ceramic as a function of the temperature in a weak ac magnetic field in the presence of a constant magnetic field have been performed. The experimental ceramic consisted of ∼3mm macrograins which formed in the process of texturization. The orientation of the c axis of the macrograins was chaotically distributed. A three-peak structure of the absorption of the ac magnetic field was observed in the imaginary part of the complex permeability in a weak constant magnetic field ∼0.1T. The behavior of this absorption structure as a function of the magnitude and orientation of the constant magnetic field, frequency, and amplitude of the ac magnetic field is analyzed. It is shown that the three-peak absorption structure in the imaginary part of the complex permeability is due to the influence of two mechanisms of the dissipation of the ac magnetic field energy: volume energy dissipation associated with pinning and surface energy dissipat...

The results of theoretical and experimental investigations of the peculiarities of the nucleation of superconductivity in the presence of a nonuniform magnetic field induced by ferromagnetic films or dots with out-of-plane magnetic anisotropy are reviewed. It is shown that the phase transition line of superconductor-ferromagnet hybrids in the H-T plane (H is an external magnetic field and T is temperature) is determined significantly by the spatial distribution of nonuniform magnetic field. It allows to control the thermodynamic and transport properties of superconductor-ferromagnet hybrids by tuning the magnetic state of the ferromagnet.

The problem of magnetic field penetration into a type-II high-temperature superconductor that is in the weakly pinned vortex-liquid phase is considered. A magnetic field on the superconductor boundary rises with time in the blow-up regime. A model hydrodynamic equation describing the magnetic induction distribu- tion in the vortex-liquid phase for thermomagnetic motion of the flux is derived. Analytical expressions for the depth and rate of magnetic field penetration into the superconductor are found. It is demonstrated that these quantities depend on parameters of the problem: index of power n in the boundary regime characterizing the penetration rate of vortices into the superconducting half-space and a parameter describing the effect of random pinning forces and thermal fluctuations on the magnetic flux distribution.

Steady-state properties of Bloch domain wall (DW) in superconducting ferromagnet (SCFM) are studied. The distribution of magnetic field above and below the surface of the SCFM due to the permanent magnetization supercurrent flowing in the DW plane is calculated by solving Maxwell equations supplemented by London equation. It is shown that part of the magnetic flux of the two neighboring domains closures in the nearest vicinity of the surface of the sample giving rise to declination of the line of the force from being parallel to the DW plane. As a result, the value of the normal component of magnetic field at the surface of the sample reaches only half of the value of the bulk magnetic flux. At the distances of the order of value of London penetration depth the magnetic field decreases as inverse power law due to the long-range character of dipole-dipole interaction. The last two circumstances are important for comparison the calculated magnetic field with the data obtained by the methods on measurement of normal component of magnetic field, e. g. Hall probe technique, aimed to confirm the existence of magnetic order parameter in unconventional superconductor., Comment: 5 pages, 4 figures

A composite consisting of the powder of Bi system and resin was produced to discuss the absorption effect on the X band microwave. Prior to the production of the absorber, the method of measuring, calculating and thickness on the material constant were discussed, followed by the preparation of the material. Then, the absorption performance for the microwave was evaluated. The experimental results showed that the composite produced tends to increase the reflection loss in accordance with the increase of the content of the powder of the system at room temperature. On the other hand, it weas found that the composite does not absorb the microwave at the temperature of liquid nitrogen because of its superdiamagnetism. Then, it was concluded that the composite prepared can be used as the microwave absorber at room temperature while it can be used as the shielding medium of the microwave at the temperature of liquid nitrogen.

A charged, near degenerate quantum fluid, necessarily inhomogeneous by virtue of the presence of a dynamic and more massive compensating charge distribution (itself possessing internal structure composed in part of the same particles constituting the putative quantum fluid) is found to exhibit a liquid–liquid phase transition as temperature is lowered. The ensuing low temperature phase is dissipationless and in spite of long-ranged attractions between the quantum fluid and the compensating system, no energy transfer proceeds between the two. The quantum fluid in question is electronic in origin; the emerging state is, of course, one of superconductivity or superdiamagnetism and its lack of dissipation is entirely consistent with the existence of an energy gap in the spectrum of excitations of the quantum fluid. The degeneracy temperature of the quantum fluid originates with valence electrons, and ranges from 10 4 to 10 5 K. There is vast flexibility in the choice of structure, the degree of complexity of the compensating system, and of its dynamics. Acknowledging fluctuations in both itinerant and localized charge, is it therefore possible that systems can be found where the liquid–liquid transition of interest here can be found at significant temperatures, perhaps even near room temperature? In this quest it appears that the light elements in combination continue to offer considerable promise.

The problem of magnetic field penetration into the half-space is considered in parallel geometry in an external magnetic field increasing with time in accordance with the law B(0, t, τ0 = B c 1 (1 + t/τ0) m , m ≥ 0, t ≥ 0 (τ 0 is the time of magnetic flux redistribution and B c 1 is the lower critical field). It is assumed that the flow of vortices is thermally activated in the “giant” creep mode (i.e., for weak pinning creep and high temperatures). A model equation is derived for describing the magnetic flux evolution. Analytic formulas are obtained for the depth and velocity of magnetic field penetration. It is shown that the giant creep regime is stable for 0 ≤ m ≤ 1/2.

The specific heat capacity of a magnetite-based magnetic fluid and changes in the magnetic part of the molar heat capacity of its magnetic phase in magnetic fields of 0–0.7 T were determined calorimetrically over the temperature range 288–353 K. The temperature dependence of changes in the magnetic part of entropy in an applied magnetic field was calculated. It was found that the field dependence of heat capacity had a maximum in fields of 0.3–0.4 T, and the temperature dependences of changes in the magnetic part of heat capacity ΔCp(H) and entropy ΔSm(H) had maxima at the magnetic phase transition temperature.

Critical currents measured on a commercial Bi-2223/Ag tape in applied magnetic fields ranging from zero to 100 mT are analysed in order to demonstrate the validity of the phenomenological description proposed by the authors for flux pinning in polycrystalline high-temperature superconductors in low magnetic fields. The four-parameter model is a generalization of the Kim formula describing the magnetic field dependence of the critical current density. When combined with the finite-element calculation, it is able to predict the critical currents measured in different field orientations with an average accuracy better than 0.2%. The volume density of the flux pinning force is easily evaluated from the parameters of the model. Particular attention is paid to the problem of a possible sample non-uniformity. In fact, the experimental data can be better explained assuming the hypothesis of better filament texturing in outer filaments. This also means that the accurate determination of critical currents in low magnetic fields can be used to reveal a non-uniformity in the current-carrying capability of the superconducting material.

It was investigated that the magnetic fluid which can be the carrier of magnetic particles or magnetic drug carrier particles (MDCP) flows surrounding a permanent magnet in a channel under the influence of high gradient magnetic field and the temperature difference between upper and lower boundaries of the channel. It is considered that the magnetization of the fluid varies linearly with temperature and magnetic field intensity. The numerical solution of above model is described by a coupled and nonlinear system of PDEs. Results indicate that the presence of magnetic and temperature fields appreciably influence the flow field; vortexes arise almost around the magnetic source and also appear near the upper left and lower right boundaries. The temperature, local skin friction coefficient and rate of heat transfer are all affected by the magnitude and position of the magnetic source, they fluctuate evidently near the high gradient magnetic field area.

The evolution of the spatial distribution of the magnetic induction in a superconductor after the action of the alternating magnetic field perpendicular to the trapped magnetic flux has been analyzed. The observed stabilization of the magnetic induction profile is attributed to the increase in the pinning force, so that the screening current density becomes subcritical. The last statement is corroborated by direct measurements.

A theoretical analysis is presented of the dependence of the thermoelectric power, when the temperature gradient is directed along the normal to the layers, in a layered conductor, with a quasi-two-dimensional electron energy spectrum on the magnitude and orientation of a strong magnetic field relative to the layers. The angular oscillations of the thermoelectric power, when the magnetic field is noticeably tilted from the normal to the layers result from the periodic dependence of the average electron velocity on the angle between the normal to the layers and the magnetic field. It is shown that, in a quantizing magnetic field at low temperatures, giant quantum oscillations of thermoelectric power as a function of both the magnetic field magnitude and the angle between the normal to the layers and the magnetic field occur. This quantum oscillation effect can be used with a high degree of accuracy as a good spectroscopic method for the experimental study of certain characteristics of a Fermi surface of quasi-two-dimensional organic conductors, such as the quasi-two-dimensionality parameter of the electron energy spectrum, cyclotron effective electron mass, and velocity distribution of charge carriers as well as an accurate determination of the extremal cross sections. PACS No.: 72.15.Jf

Effects of Ag₂O doping on the electromagnetic properties in the BiSrCaCuO superconductors. The electromagnetic properties of the Ag₂O doped and undoped BiSrCaCuO superconductor were evaluated to investigate the contribution of the pinning centers to the magnetic effect. It was confirmed experimentally that a large amount of magnetic flux was trapped in the Ag₂O doped sample than that in the undoped one, indicating that the pinning centers of magnetic flux are related closely to the occurrence of the magnetic effect. It is considered that the area where normal conduction takes place increases by adding Ag₂O and the magnetic flux penetrating through the sample increases. The results suggested that Ag acts to increase the pinning centers of the magnetic flux, contributing to the occurrence of the electromagnetic properties.

The series of rare earth (R)-3d transition metal (T)-semiconductor(S) with structural formula of RT 2 S 2 have received much attention due to their complicate low temperature magnetic properties such as metamagneticantiferromagnetic, pauli paramagnetic, commensurate-incommensurate magnetic phase transition1,2. However, the magnetisms of these magnetic phenomena are not very clear. In recent years, the complicate magnetic phase states at low temperature could be understood by the skyrmion effect3. A topological magnetism might be used to interpret these magnetic phenomena. In addition, the high temperature magnetic property and the magneto-transport should be an extensive study in RT S system.

One of the phenomena that make superconductors unique materials is the Meissner-Ochsenfeld effect. This effect results in a state in which an applied magnetic field is expelled from the bulk of the material because of the circulation near its surface of resistance-free currents, also known as Meissner currents. Notwithstanding the intense research on the Meissner state, local fields due to the interaction of Meissner currents with pinning centres have not received much attention. Here we report that the Meissner currents, when flowing through an area containing a pinning centre, generate in its vicinity two opposite sense current half-loops producing a bound vortex–antivortex pair, which eventually may transform into a fully developed vortex–antivortex pair ultimately separated in space. The generation of such vortex dipoles by Meissner currents is not restricted to superconductors; similar topological excitations may be present in other systems with Meissner-like phases. A Meissner current is the resistance-free flow of charge induced by magnetic field in a superconductor. Here, the authors observe that Meissner currents flowing through an area containing a pinning centre generate two opposite-sense current half-loops that produce a bound vortex–antivortex pair.