Perfect Diamagnetism Research Articles

Magnetization anomalies in one-dimensional halogen-bridged paltinum complex: Field-induced diamagnetic transition and antiferromagnetism

We present dc magnetization measurements on one-dimensional iodine-bridged platinum complex which demonstrates a magnetic-field-induced diamagnetic transition and an antiferromagnetic ordering. This is the first evidence for a field-induced transition in a one-dimensional insulator. The crystals were synthesized from a solution of [Pt(en)2]1-k[Pt(en)2I2]1+k(CIO4)2 (0≤k≤1). Depending on temperature, field intensity and sample quality, a paramagnetism, antiferromagnetism and diamagnetic-paramagnetic transition were observed. The diamagnetic signals as large as 0.5–16.5 % of that for perfect diamagnetism (Meissner effect) were observed over a wide temperature range. Sharp field-induced transition from diamagnetism to paramagnetism occurred around 180 K. The crystallization from a molar imbalance solution leads to disordered platinum configuration (e.g. PtII-I-PtIII-I-PtIII-I-PtIII). The magnetization anomalies may be attributed to such a disorder.

Preparation of the oxide superconductors (La,Gd,Ba,Ce)8Cu6Oz and (La,Gd,Ba,Sr,Ce)8Cu6Oz.

We have synthesized nearly single-phase [(${\mathrm{Gd}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{La}}_{\mathit{x}}$${)}_{1/2}$${\mathrm{Ba}}_{1/3}$${\mathrm{Ce}}_{16}$${]}_{8}$${\mathrm{CU}}_{6}$${\mathrm{O}}_{\mathit{z}}$ (x=0, (1/3, (1/2) and single-phase [${\mathrm{La}}_{1/6}$${\mathrm{Gd}}_{1/3}$(${\mathrm{Ba}}_{1\mathrm{\ensuremath{-}}\mathit{y}}$${\mathrm{Sr}}_{\mathit{y}}$${)}_{1/3}$${\mathrm{Ce}}_{1/6}$${]}_{8}$${\mathrm{Cu}}_{6}$${\mathrm{O}}_{\mathit{z}}$ (y=(1/4, (1/2). The x-ray-diffraction patterns were successfully indexed for tetragonal unit cells of approximately the same dimension with the lattice parameters of a=3.830\char21{}3.858 A\r{} and c=28.298\char21{}28.489 A\r{}. (${\mathrm{La}}_{1/6}$${\mathrm{Gd}}_{1/3}$${\mathrm{Ba}}_{1/6}$${\mathrm{Sr}}_{1/6}$${\mathrm{Ce}}_{1/6}$${)}_{8}$${\mathrm{CU}}_{6}$${\mathrm{O}}_{18.83}$, which was annealed at a high oxygen pressure of P(${\mathrm{O}}_{2}$)=200 atm, exhibited a metallic temperature dependence of resistivity, and a very sharp superconducting transition at ${T}_{c}^{\mathrm{on}=39}$ K (${T}_{c}^{R=0}$=36 K). The Meissner signal at 10 K of this sample was about 35% of the perfect diamagnet.

Ｙ系酸化物超電導体の透磁率と反強磁性

It is wellknown that Cu-O chains indicate superexchange interaction which is the origin of antiferromagnetism. YBCO perovskite has the chains which also originates high-Tc superconductivity. So we focused to the magnetism of superconducting samples at normal conductivity state and cleared the correlation between the antiferromagnetism and the high-Tc superconductivityTo investigate the antiferromagnetism, the experiments were carried out by measuring the relative magnetic permeability(μs) at 77K and room tempreture. The samples which Cu molar ratio, X was changed from 2.5 to 3.5 in YBa Cu O7-δ were used to study Cu molar ratio dependence on μs in Cu-O chains. The samples which pelet forming pressure were varied from 400 to 800kg/cm2 were used in this study. Perfect diamagnetism was observed in each sample at 77K, except sample of X=2.5 which showed a value of about 1. The samples of 2.8<X<3.5 indicate antiferromagnetism at room temprature. The antiferromagnetism was the strongest at X=3.0 which was most suitable composition for high-Tc superconductors and this sample showed the highest Tc end and Jc.

Intralattice Strain Analysis in Superconducting Crystals and Superconducting Electrons

AbstractThe bonding distances between atoms in five different structure types of superconductors, Nb3Sn, (La, Sr)2CuO4, YBa2Cu3O7–δ, Bi2Sr2CaCu2Ox and Tl2Ca2Ba2Cu3O8+x were calculated. There are many shrunken bonds in all the five compounds. Tc increases with the decrease in atomic distance of cations, rather than that of Cu–O. Structures which have large rhombicity tends to have higher density without the application of ultra‐high pressure owing to the existence of a large number of oxygen; that is, the more the number of oxygen anions surrounding the cations increases, the more the radii of cations shrink. In shrunken atoms, electron orbits are forced to condense toward to the nucleus, it is considered that superconducting electrons are apparently created and perfect diamagnetism is derived from inner filled bands.

The electric field induced by a gravitational wave in a superconductor: a principle for a new gravitational wave antenna

In this paper we investigate the effect of gravitational waves (GW) on a superconductor. We find that the key properties of a superconductor, namely zero resistance and perfect diamagnetism, give rise to an important new effect, the presence of an induced electric fieldE(r, t) in the interior of the superconductor. TheE field reacts with the ions and superelectrons. We argue, that not only is the finding of the coupled interactions of gravitation, electromagnetism and superconductivity inherently interesting, but that the inducedE field might provide a significantly more sensitive means of detecting gravitational waves. It appears likely that existing resonant-mass superconducting antennas withL ∼- 3m,Q ∼- 108 could be readily modified to detectE fields induced by GWs of dimensionless amplitudeh ∼- 10−24

Observation of superconductivity in the organometallic intercalation compound SnSe2{Co(η-C5H5)2}0.33

Intercalation of phosphorus-doped SnSe2 with bis(cyclopentadienyl) cobalt {Co(η5-C5H5)2} produces superconducting SnSe2{Co(η5-C5H5)2}0.33 with a critical temperature of 6 K; magnetisation measurements show a hysteresis loop with a maximum at 40 G, indicating type II superconducting behaviour; the lower critical field (Bc1) is estimated at 10 G at 4.2 K and the critical current density (Ic) is ca. 500 A cm–2 at 2.5 K; the diamagnetic susceptibility corresponds to 13% of perfect diamagnetism.

Chemical and physical properties of a new ambient pressure organic superconductor with Tc higher than 10K

An overview of the chemical and physical properties of a new organic superconductor (BEDT-TTF) 2Cu(NCS) 2, of which Tc (10.4–11.0K) is the highest among those of organic superconductors so far known, is presented. Distorted-hexagon-shaped crystals of the Cu(NCS) 2 salt were prepared by the electrochemical oxidation of BEDT-TTF in 1,1,2-trichloroethane in the presence of CuSCN, KSCN, and 18-crown-6 ether (or K +(18-crown-6 ether)Cu(NCS) 2 − complex, or CuSCN and TBA·SCN, as a supporting electrolyte) under a constant current of 1–5 μA. The black shinny crystals were stable against air and moisture and start to decompose above 190°C detected by DSC, TG and DTG. The crystal structures indicate that both lattice parameters and packing pattern of BEDT-TTF molecules are almost the same to those of κ-(BEDT-TTF) 2I 3 salt (Tc=3.6K) despite the considerable difference of Tc between them. Two BEDT-TTF molecules are dimerized and the dimers are linked one another by short sulfur.. sulfur atomic contacts to construct two-dimensional conducting BEDT-TTF sheets in the bc-plane. The anions, Cu(NCS) 2 −, form one-dimensional zigzag polymer along the b-axis and the polymers construct insulating sheets in the bc-plane. Every conducting layer is sandwiched by the insulating layers along the a-axis. Two kinds of layers are linked by hydrogen bonds between terminal ethylene groups of BEDT-TTF and nitrogen and sulfur atoms of the anions. Due to the lack of the inversion center of the crystal, the space group is lowered from P2 1/c of κ-(BEDT-TTF) 2I 3 to P2 1. Owing to this symmetry the Cu(NCS) 2 salt is optically active (specific rotatory power is about 230° at 632.8nm) and the Fermi surface based on extended Hückel MO is composed of both a cylindrical closed surface (18% of the first Brillouin zone) and a modulated quasi-one-dimensional open surface. Tc of the BEDT-TTF-h 8 salt is 10.2–10.4K by four-probe d.c. resistivity measurements and Tc decreases with increasing pressure. An inverse isotope effect was observed in our samples so far measured (more than seven each samples). The deuterated samples showed higher Tc by 0.5K measured by the RF penetration depth measurements. Magnetic susceptibility measurements indicate that the salt is non-ideal class II superconductor and almost 100% of the perfect diamagnetism was observed below 7K. Upper critical field measurements showed a dimensional cross-over-like behavior (3D to 2D) when the external field is parallel to the 2D plane. Hc 2 values at 6K were about 13T and 0.5T in the 2D plane and normal to it, respectively. The estimated anisotropy in the GL coherence length from the critical field near Tc is ξ bc(0):ξ a∗(0)=182 A ̊ :9.6 A ̊ =19:1 . The Shubnikov-de Haas signal was observed below 1K and above 8T. The period of 0.0015T −1 corresponds to the area of extremal orbit of 18% of the first Brillouin zone. The anisotropic nature of the thermoelectric power of the crystal in the 2D plane can be explained on the basis of the complicated Fermi surface. No EPR signal ascribed to Cu 2+ was observed. The linewidth of the EPR signal of BEDT-TTF + increased monotonically with decreasing temperature in contrast to the predictions of the Elliot formula for the spin relaxation in metals. A Korringa relation was observed in 1H NMR measurements between 77K and 10K. Below 10K a big enhancement of the relaxation rate was observed with a peak at considerably lower temperature than Tc. Anisotropic superconducting gaps were detected by tunneling spectroscopic work. Tc of several BEDT-TTF superconductors were discussed on the basis of the effective volume of one electron for the molecular design of new organic superconductors.

A new concept of magnetic thin-film heads with superconductors

A new concept of the thin-film heads for magnetic recording introduced in this paper is to use the superconductive film as a perfect diamagnet to be the gap medium between the two magnetic poles of a thin-film ring head for the longitudinal magnetic recording. By using the finite-element method, the magnetic field and its distribution for the new designed ring head with a single-layer superconductive film or multilayer structure as the medium between the magnetic poles is calculated. The results show that the diamagnetic film in the gap not only increases the amplitude of the magnetic field in front of the magnetic poles, but also makes the distribution of the magnetic field much sharper, and the amplitude of the field is less influenced by the throat height of the pole tip as well.

Bulk Superconductivity in (BEDT-TTF)2[Cu(NCS)2

Abstract The diamagnetic shielding is observed for an ambient-pressure organic superconductor (BEDT-TTF)2[Cu(NCS)2] by means of a.c. susceptibility measurements. The diamagnetic susceptibility amounts to 100 ± 5% of the perfect diamagnetism below 7 K and exhibits a sharp transition at 10.3 ± 0.4 K. The thermodynamical critical field is estimated and discussed in terms of the BCS theory.

Meissner Effect in an Organic Superconductor (BEDT-TTF)2[Cu(NCS)2

Abstract A quite large diamagnetic susceptibility corresponding to 83% of the perfect diamagnetism is observed for (BEDT-TTF)2[Cu(NCS)2] at 2 K. The critical temperature is determined to be 9.8±0.3 K at 30 G. The magnetization shows a hysteresis loop with sharp maxima near 35 G, thereby indicating the type II superconducting nature. The lower critical field and the critical current density are estimated from the analysis of the hysteresis loop.

Magnetic studies on the high temperature oxide superconductor Eu0.4Gd0.6Ba2Cu3O7− δ

The oxide Eu 0.4 Gd 0.6 Ba 2 Cu 3 O 7− δ is superconducting with a transition temperature above liquid nitrogen temperature. We have carried out detailed magnetic studies on this compound. Low field dc susceptibility measurements and four probe electrical resistivity measurements yield a superconducting transition temperature of about 78 K. Measurements of the shielding effect give a value of 82% of the corresponding value for perfect diamagnetism. The lower critical field is found to be 600 Oe at 4.2 K. The hysteresis loop has been obtained at 4.2 K in fields up to 90 kOe from which the magnetic critical current density has been estimated. Above the superconducting transition temperature, the magnetic susceptibility of this compound is close to that of an assemblage of Gd 3+ ions. In the superconducting state it is observed that, because of field penetration, the paramagnetism of the Gd 3+ ion overtakes the diamagnetism of the material in an external field of about 5 kOe.

Equilibrium of a magnet floating above a superconducting disk

A superconducting body will repel a nearby magnet. The repulsion is due to the perfect diamagnetism resulting from the Meissner effect. A small magnet will float above a superconducting disk at an equilibrium position over the disk center, stable against lateral displacements. It is not intuitively obvious why the potential energy of the magnet over a flat disk should have a minimum at the center, rather than a maximum. We have measured the properties of the attractive potential well of a YBa2Cu3O7 disk by two experiments. In the first, we use a low-frequency magnetic field, 0–100 Hz, to excite oscillations of a small, freely levitating bar magnet about its equilibrium position. We find sharp resonances, corresponding to longitudinal, transverse, and torsional modes of oscillation. The frequencies of these resonances define the properties near the bottom of the potential well. In the second experiment, we attach the magnet to a vertical glass fiber of known stiffness. The magnet is suspended horizontally a small known distance, z, above the superconducting disk. By moving the magnet from the center of the disk to the edge and measuring the bending of the support fiber as a function of position we determine the shape of the potential curve for large displacements and the total energy needed to escape from the well.

Meissner effect in Y-Ba-Cu-O and La-Sr-Cu-O high-temperature superconductors.

Measurements of the static magnetic susceptibility confirm the existence of significant Meissner flux expulsion in the high-temperature superconductors ${\mathrm{Y}}_{1.2}$${\mathrm{Ba}}_{0.8}$${\mathrm{CuO}}_{4}$ and ${\mathrm{La}}_{1.85}$${\mathrm{Sr}}_{0.15}$${\mathrm{CuO}}_{4}$ below the onset temperatures of 85 and 39 K, respectively. The Y-Ba-Cu-O sample contains both superconducting and nonsuperconducting phases. The observed Meissner effect corresponds at 20 G to at least 20% of perfect diamagnetism in the black superconducting phase. For the single-phase La-Sr-Cu-O compound the Meissner signal at 10 G reaches a value corresponding to at least 24% of perfect diamagnetism.

Anomalous Magnetism of the High-Tc Superconductors with Rare-Earth and/or Transition Element Ions–Static Susceptibility with Resistivity–

A series of the high-Tc superconductors Y–Ba–Cu–O system substituted Y– by rare earth ions Eu–, Gd–, Ho– or/and –Cu– by transition element ions –Mn–, –Ni– have been studied at 4.2∼120K from a stand-point of magnetism by using a microwave SQUID at 9 GHz. Anomalous coexistence of the magnetic phase with perfect diamagnetism in Ho–Ba–Cu–Oxide has been observed, whereas substitution of –Cu– by transition element ions yields delicate effects on superconductivity.

Bulk Superconductivity in La2CuO4

There is considerable interest in the interplay, of superconductivity and magnetism in La2CuO4. Several groups [1–3] have noted signs of superconductivity in nominal La2CuO4, and antiferromagnetism has been reported[4] in La2CuO4-y with y&gt;0. The superconductivity previously reported was of a filamentary nature because although resistance drops to near zero were observed, only small Meissner effects (∼10-3 to 10-4 of perfect diamagnetism) were observed. In this paper we describe our studies of. ceramic samples of La2CuO4-y, loaded with oxygen by high pressure. This technique results in substantial incorporation of O2 in the material (of the order of 0.3 to 0.4% by weight) and in gross changes in the bulk resistivity and magnetization as well as discernable changes in the lattice parameters of the material.

Fractional quantized Hall effect: Perfect differential diamagnetism and paramagnetism

The fractional quantized Hall effect yields alternating perfect diamagnetism and paramagnetism. The latter is related to the formation of a domain structure. This structure alters the dependence of magnetoresistance and Hall resistance on a magnetic field.

Infinite conductivity and perfect diamagnetism in type-I superconductors

A calculation of the paramagnetic current suggests how infinite conductivity can lead to perfect diamagnetism in soft superconductors in a stationary state.

Experimental tests for boson condensation and superconductivity in semiconductors during pulsed beam annealing

Van Vechten and Compaan and, independently, Nagy and Noga have proposed that the high reflectivity state observed in pulsed laser/electron/ion beam annealing of Si and other semiconductors results when the electron-hole plasma created by the initial absorption of the ionizing radiation undergoes a boson condensation. The condensed state is described in the same form as the BCS superconductor and has many of the properties of the superconducting state. Lattice temperatures for the material during this phase have beeb measured by Raman scattering to lie in the range from 500 to 1000 K. At this writing no magnetic experiment has been completed to test this proposition further. In addition to the practical problems associated with such a test, there are theoretical questions such as whether or not the bipolar plasma ought to be able to expel a magnetic field within the 100 ns or so that it persists in the proposed boson condensed phase. If not, it does not exhibit perfect diamagnetism and the Meissner effect. An experiment is proposed that is argued to be both easy to perform and to offer a conclusive demonstration of boson condensation. The proposed experiment involves observation of the single plasmon mode by diffraction or from the appearance of linear ripples left on the solid surface and the rotation of this pattern. Preliminary observations seem to confirm the condensation.

Magnetic properties of superconducting DyxCe1-xRu2

The magnetisation of DyxCe1-xRu2 (x=0 to 1) has been measured at temperatures ranging from 1.5 to 300K. In the alloys with concentration in the range of 0.15<or=x<0.24, two critical temperatures, i.e. a superconducting transition temperature and a paramagnetic Curie temperature have been observed at low temperatures, but no ferromagnetic hysteresis has been found that the observed total magnetisation can be expressed by the sum of the superconducting magnetisation and the normal state (nonsuperconducting) magnetisation and that this expression holds whether the field is smaller than Hc1 or not. The magnitude of the initial slope of the magnetisation against magnetic field curve decreases with increasing x and is smaller than that of the perfect diamagnet. A domain structure model composed of superconducting domains and nonsuperconducting domain boundaries, is proposed to explain the present experimental results.

An Introduction to Superconductivity

Superconductivity—the absence of electrical resistance below a certain temperature Tc, is a phenomenon discovered by Kammerlingh Onnes in 1911. Resistivity can be restored either by increasing the temperature above Tc or by applying a magnetic field greater than a critical field Hc for the material. A superconductor can be said to have both infinite conductivity and perfect diamagnetism. Litterally hundreds of elements and alloys have been found to exhibit this property. The highest Tc for any compound is about 23°K. The technological importance of a resistanceless conductor is enormous and in spite of high operating costs (because superconductors have to be maintained below 23°K) applications are multiplying. Superconducting power transmission lines, MHD power generation, synchronous generators with superconducting rotors and magnets for the plasma confinement in fusion reactors are subjects of large research programs in the industrialized countries all over the world. Josephson Junction device has potential as an RF detector, mixer, parametric amplifier and up convertor, oscillator, frequency multiplier and divider, ultrafast logic gate and switch.