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We observe sharp step-down discontinuities in the magnetic susceptibility of NH4H2PO4 and NH4H2PO4-d60 (60% deuterated) along the a- and c-axes occurring exactly at their antiferroelectric transiti...

Most ferroelectric crystals have their own set of unique characteristics, and ammonium sulfate (NH4)2SO4 is no exception. We report on two previously unidentified features in ammonium sulfate: (1) ...

The associated magnetic moments of the periodic rotational motion of methyl groups in hexamethylbenzene C$_6$(CH$_3$)$_6$ were recently identified to contribute to its overall magnetic susceptibility. Those measurements however, were only performed on hydrogenous polycrystalline samples. We report magnetic susceptibility measurements on single crystalline C$_6$(CH$_3$)$_6$ in the cases where the applied magnetic field is parallel and perpendicular to the molecular basal planes. In the former case, metastable behavior near the onset temperature T$_{C-H}$=118 K is identified while in the latter, no anomalous behavior is observed. Similar anomalies are observed in deuterated hexamethylbenzene C$_6$(CD$_3$)$_6$ (where D is deuterium), however, T$_{C-D}$ occurs 14 K higher at 132 K. In addition, a peak anomaly identified near 42 K is suggested to be due to the onset of coherent quantum tunneling of deuterons. The near cubic ground state is proposed to be the result of a more radical form of the Jahn-Teller effect occurring in a molecular solid where the lattice distorts to remove the orbital degeneracies of the protons to lower its energy. The apparent magnetic anisotropy and isotope effect provide evidence that apart from electrons, not only protons, but also deuterons establish strongly correlated behavior., Comment: 21 pages (double spaced), 4 figures + 2 supplementary figures, Just Accepted Manuscript by the Journal of Physical Chemistry C

The polarity of the magnetic susceptibility χ(T) of ammonium alum NH4Al(SO4)2•12H2O single crystals below its ferroelectric Curie temperature TC is identified to depend only on the cooling rate. To explain this, we consider reorienting distorted NH4+ to carry weak magnetic and electric dipole moments that are linearly coupled. Slow cooling allows the dipole moments to align which enhances χ(T) to become positive. However, due to energy degeneracy of rotational motion and geometric frustration of the NH4+, faster cooling rates render the system to become an orientational glass state causing χ(T) to remain negative. Specific heat measurements also show the presence of excess entropy below a negative anomaly near 53 K. Our findings identify a possible new class of non-equilibrium system with potential applications in non-volatile memory devices.

A linear induction motor system composed of a high– T c superconducting secondary with close-ended coils made of REBCO coated conductor wire was designed and tested experimentally. The measured thrust, normal force and power loss are presented and explained by combining the flux dynamics inside superconductors with existing linear drive theory. It is found that an inherent capacitive component associated to the flux motion of vortices in the Type-II superconductor reduces the impedance of the coils; from such, the associated Lorentz forces are drastically increased. The resulting breakout thrust of the designed linear motor system was found to be extremely high (up to 4.7 kN/m 2 ) while the associated normal forces only a fraction of the thrust. Compared to its conventional counterparts, high- T c superconducting secondaries appear to be more feasible for use in maglev propulsion and electromagnetic launchers.

Epitaxy and misfit strain imposed by underlying substrates have been intensively used to tailor the microstructure and electronic properties of oxide films, but this approach is largely restricted by commercially limited substrates. In contrast to the conventional epitaxial misfit strains with a positive Poisson’s constant, we show here a tunable Poisson’s ratio with anomalous values from negative, zero, to positive. This permits effective control over the out-of-plane lattice parameters that strongly correlate the magnetic and transport properties in perovskite mixed-valence La1–xSrxMnO3 thin films. Our results provide an unconventional approach to better modulation and understanding of elastic-mediated microstructures and physical properties of oxide films by engineering the Poisson’s ratios.

As a follow-up of our previous work on pressure-induced metallization of the 2H_{c}-MoS_{2} [Chi et al., Phys. Rev. Lett. 113, 036802 (2014)PRLTAO0031-900710.1103/PhysRevLett.113.036802], here we extend pressure beyond the megabar range to seek after superconductivity via electrical transport measurements. We found that superconductivity emerges in the 2H_{a}-MoS_{2} with an onset critical temperature T_{c} of ca. 3 K at ca. 90 GPa. Upon further increasing the pressure, T_{c} is rapidly enhanced beyond 10 K and stabilized at ca. 12 K over a wide pressure range up to 220 GPa. Synchrotron x-ray diffraction measurements evidenced no further structural phase transition, decomposition, and amorphization up to 155 GPa, implying an intrinsic superconductivity in the 2H_{a}-MoS_{2}. DFT calculations suggest that the emergence of pressure-induced superconductivity is intimately linked to the emergence of a new flat Fermi pocket in the electronic structure. Our finding represents an alternative strategy for achieving superconductivity in 2H-MoS_{2} in addition to chemical intercalation and electrostatic gating.

The methyl groups in hexamethylbenzene C$_6$(CH$_3$)$_6$ become magnetically ordered at the molecular level below 118 K. This is also near the temperature at which the system structurally transitions from triclinic to a unique near-cubic phase. High-precision measurements of the near-static dielectric constant reveal that the structural phase transition is actually comprised of four successive transformations upon cooling at T$_1$=110.7 K, T$_2$=109.5 K, T$_3$=109.1 K and T$_4$=107.8 K. In contrast to warming, only two transitions occur at T'$_4$=119.2 K and T'$_1$=120.9 K. The methyl groups in the near-cubic phase become slightly distorted according to existing neutron powder diffraction measurements. Analysis of the 2$^6$=64 possible spin orientation configurations of the methyl groups reveal a 20-fold ground state degeneracy presiding in each molecule rendering the system to become highly unstable. From such, it is interpreted that T$_1$ and T$_2$ are temperatures at which the molecules successively lower their symmetry to remove the energy degeneracy which involve methyl group elongation and further out-of-plane tilting. This triggers the system to phase transition into the near-cubic phase which involves a shearing of the molecular planes and partial rotation of the methyl groups at T$_3$ and T$_4$. We interpret the low temperature near-cubic phase to be a manifestation of Jahn-Teller distortions based on energy degeneracies of the orbital motion of protons in each molecule and suggest that the metastable nature of the phase transition originates from the methyl groups requiring a larger amount of energy to order than to disorder. Our findings help explain why many unusual structural phase transitions occur at low temperatures in other molecular crystals possessing periodic motion of protons., Comment: 14 pages (1.5 spaced, 3 figures + 1 'Table of Contents' graphic; accepted (on Dec. 4th, 2018) by the Journal of Physical Chemistry C

The electrical properties of a close-ended coil made of REBCO-coated conductor wire are studied via the measurement of its induced currents upon exposure to a sinusoidal magnetic field at different frequency. Results show a similarity to the behavior of currents inside an RLC circuit where the peak amplitude is dependent on the contact resistance of the solder joining the two ends of the coil and the resonant frequency, i.e., a function of the inductance of the coil and penetration rate of fluxons into the superconducting layers. Our findings suggest highly feasible applications stemming from such experimental setup in the field of linear and rotating machinery and low-frequency high-quality-factor resonators.

In order to optimize the structure of high temperature superconducting coils for linear motor applications, three separate coils with different shapes made of Re-BCO coated conductor were studied: circular shaped single pancake, circular shaped double-pancake and racetrack shaped single-pancake. The thrust and vertical forces of the three coils above a conventional flat linear three-phases winding were investigated experimentally. With the aid of the experimentally obtained values, it was found that single-pancake coil in the shape of a racetrack was the best selection for a flat single-sided linear motor system. Studies were also made on the frequency characteristics of the vertical force of the racetrack shaped single-pancake coil.

The potential application of bulk high temperature superconductor (HTS) magnets has attracted much attention because of the potential high trapped flux in HTS magnets. This paper focuses on the magnetization method design of bulk multi-seeded HTS magnets for obtaining their better flux-trapping performance. Firstly, three different magnetization methods were carried out based on the current experimental setup to find a better way of magnetizing a bulk melt-texture three-seeded YBaCuO superconductor. The experimental results indicated that when the three domains of this three-seeded YBaCuO bulk were magnetized in order, the maximum trapped flux was higher than that when only one domain was magnetized. However, this method costs about three times of the magnetization time than the other two methods and the increasing ratio was only about 11.11%. It has been found that another method of magnetizing only the middle domain could also get a good result such as the uniformity of trapped flux is good. In order to improve the current experimental magnetization conditions for further improvement, two sheets of iron were designed to attach two poles of the electromagnet (Lakeshore, Model EM4-CV) for increasing the magnetizing area, and that all domains of a bulk multi-seeded HTS can be magnetized in one time. Firstly, the appropriate size and thickness of the iron sheets was simulated and optimized by Comsol Multiphysics. It has been found that the magnetic field between two poles was highest when the thickness of iron was 2 mm and the length was 68 mm. Then, the simulating and optimization results had been verified by the following experiments. According to the comparison experiments, it is proved that to choose the magnetization method that only magnetizing the middle domain with the improved setup is helpful to obtain larger and more homogeneous magnetic flux for the bulk multi-seeded HTS magnet due to the added iron sheets.

High temperature superconducting (HTS) bulk sample acts as quasi-permanent magnet when it traps magnetic field, and the superconducting bulk magnet can substitute the traditional permanent magnet in the engineering of the linear motor for the purpose of achieving higher efficiency. The electromagnetic forces between the HTS bulk magnets and the ac magnetic field are the most important parameters to consider for the engineering of a motor. We measured the static vertical and thrust forces of an HTS magnet subject to a sinusoidal traveling magnetic field at different trapped fields and at different current amplitude and frequencies. The force relaxation of the HTS bulk magnet was also compared with that of a traditional permanent magnet. The feasibility of replacing the conventional magnet in the ac application machines by HTS bulk ones was preliminary validated experimentally.

High-Tc superconducting (HTS) bulk samples used for a maglev system can be re-magnetized after being subjected to another applied magnetic field which may influence the levitation performance of a HTS bulk over the permanent magnetic guideway (PMG). In order to clarify the relationship between the HTS bulk’s re-magnetization and its levitation performance, a YBCO bulk was re-magnetized at different values and its levitation performance studied experimentally above a permanent guideway (PMG) system. The results show that the increase of trapped magnetic flux inside the HTS bulk is closely related to the magnitude and direction of the applied field during the re-magnetization process. Furthermore, the levitation force changes on the HTS-PMG system affected by the re-magnetized HTS bulk are discussed allowing for optimization improvements to the maglev system load capabilities.

Temperature and field-dependent magnetization measurements on polycrystalline CeMnCuSi2 reveal that the Mn moments in this compound exhibit ordering with a ferromagnetic (FM) component ordered instead of the previously reported purely antiferromagnetic (AFM) ordering. The FM ordering temperature, Tc, is about 120 K and almost unchanged with external fields up to 50 kOe. Furthermore, an AFM component (such as in a canted spin structure) is observed to be present in this phase, and its orientation is modified rapidly by the external magnetic field. The Ce L3-edge X-ray absorption result shows that the Ce ions in this compound are nearly trivalent, very similar to that in the heavy fermion system CeCu2Si2. Large thermomagnetic irreversibility is observed between the zero-field-cooled (ZFC) and field-cooled (FC) M(T) curves below Tc indicating strong magnetocrystalline anisotropy in the ordered phase. At 5 K, a metamagnetic-type transition is observed to occur at a critical field of about 8 kOe, and this critical field decreases with increasing temperature. The FM ordering of the Mn moments in CeMnCuSi2 is consistent with the value of the intralayer Mn–Mn distance RaMn–Mn=2.890 A, which is greater than the critical value 2.865 A for FM ordering. Finally, a magnetic phase diagram is constructed for CeMnCuSi2.

Ti-sheathed MgB2 wires doped with nanosize crystalline-SiC up to a concentration of 15?wt% SiC have been fabricated, and the effects of the SiC doping on the critical current density (Jc) and other superconducting properties studied. In contrast with the previously reported results that nano-SiC doping with a doping range below 16?wt% usually enhances Jc, particularly at higher fields, our measurements show that SiC doping decreases Jc over almost the whole field range from 0 to 7.3?T at all temperatures. Furthermore, it is found that the degradation of Jc becomes stronger at higher SiC doping levels, which is also in sharp contrast with the reported results that Jc is usually optimized at doping levels near 10?wt% SiC. Our results indicate that these negative effects on Jc could be attributed to the absence of significant effective pinning centres (mainly Mg2Si) due to the high chemical stability of the crystalline-SiC particles.

Ti-sheathed monocore MgB 2 wires with improved magnetic critical current density ( J c ) have been fabricated by in situ powder-in-tube (PIT) method and characterized by magnetization, X-ray diffraction, scanning electron microscopy and electrical resistivity measurements. For the best wire, the magnetic J c values at 5 K and fields of 2 T, 5 T, and 8 T are 4.1 × 10 5 A/cm 2 , 7.8 × 10 4 A/cm 2 , and 1.4 × 10 4 A/cm 2 , respectively. At 20 K and fields of 0.5 T and 3 T, the J c values are about 3.6 × 10 5 A/cm 2 and 3.1 × 10 4 A/cm 2 , respectively, which are much higher than those of the Fe-sheathed mono-core MgB 2 wires fabricated with the same in situ PIT process and under the same fabricating conditions. It appears that the overall J c for the average Ti-sheathed wires is comparable to that of the Fe-sheathed wires. Our X-ray diffraction and scanning electron microscopy analysis indicates that J c in the Ti-sheathed MgB 2 wires can be strongly suppressed by MgO impurities and micro-cracks.

From high precision measurements of the complex dielectric constant of H2O ice, we identify the critical temperatures of the phase transition into and out of ice XI from ice Ih to occur at T_Ih-IX=58.9 K and T_IX-Ih=73.4 K. For D2O, T_Ih-IX=63.7 K and T_IX-Ih=78.2 K. A triple point is identified to exist at 0.07 GPa and 73.4 K for H2O and 0.08 GPa and 78.2 K for D2O where ices Ih, II and XI coexist. A first order phase transition with kinetic broadening associated to proton ordering dynamics is identified at 100 K., 11 pages, 5 figures

Working towards developing lightweight superconducting magnets for future space and other applications, we have successfully fabricated mono-core Ti-sheathed MgB2 wires by the powder-in-tube method. The wires were characterized by magnetization, electrical resistivity, x-ray diffraction, scanning electron microscopy, and energy dispersive spectrometry measurements. The results indicate that the Ti sheath does not react with the magnesium and boron, and the present wire rolling process can produce MgB2 wires with a superconducting volume fraction of at least 64% in the core. Using the Bean model, it was found that at 5 K, the magnetic critical current densities, Jc, measured in magnetic fields of 0, 5, and 8 T are about 4.2 × 105, 3.6 × 104, and 1.4 × 104 A cm−2, respectively. At 20 K and 0 T, the magnetic Jc is about 2.4 × 105 A cm−2. These results show that at zero and low fields, the values of the magnetic Jc for Ti-sheathed MgB2 wires are comparable with the best results available for the Fe-sheathed MgB2 wires. At high fields, however, the Jc for Ti-sheathed MgB2 wires appears higher than that for the Fe-sheathed MgB2 wires.

Growth anisotropies of bulk high temperature superconductors (HTSCs) fabricated by a top-seeded melt texture growth process, that is, different pinning effect in the growth sectors (GSs) and growth sector boundaries (GSBs), possess effect on the macro flux trapping and levitation performance of bulk HTSCs. Previous work (Physics Procedia, 36 (2012) 1043) has found that the bulk HTSC array with aligned GSB pattern (AGSBP) exhibits better capability for levitation and suppression of levitation force decay above a permanent magnet guideway (PMG) compared with misaligned GSB pattern (MGSBP). In this paper, we further examine this growth anisotropy effect on the maglev performance of a double-layer bulk HTSC. In contrast to reported trapped flux cases (Supercond. Sci. Technol. 19 (2006) S466), the two superposed bulk HTSCs with same AGSBP with PMG are found to show better maglev performance. These series of results are helpful and support a new way for the performance optimization of present HTS maglev systems.

A method to transport up to 180 A of current into the sample space of a pressure cell without causing thermal instabilities at 77 K was developed in order to study the critical current Ic of samples of first-generation Bi-2223 superconducting wire at different hydrostatic pressures. Ic was found to linearly decrease with increasing application of external pressure and was found to be irreversible upon release of pressure. The n-value of the voltage-current curves at different pressure was also found to systematically decrease. The decrease in Ic and the irreversibility effect is attributed to the deformation of the filamentary walls of the wire.

MnWO 4 has attracted attention because of its ferroelectric property induced by frustrated helical spin order. Strong spin–lattice interaction is necessary to explain ferroelectricity associated with this type of magnetic order. We have conducted thermal expansion measurements along the a, b, c axes revealing the existence of strong anisotropic lattice anomalies at T 1 = 7.8 K , the temperature of the magnetic lock-in transition into a commensurate low-temperature (reentrant paraelectric) phase. The effect of hydrostatic pressure up to 1.8 GPa on the FE phase is investigated by measuring the dielectric constant and the FE polarization. The low-temperature commensurate and paraelectric phase is stabilized and the stability range of the ferroelectric phase is diminished under pressure.

Multiferroic rare earth manganites attracted recent attention because of the coexistence of different types of magnetic and ferroelectric orders resulting in complex phase diagrams and a wealth of physical phenomena. The coupling and mutual interference of the different orders and the large magnetoelectric effect observed in several compounds are of fundamental interest and bear the potential for future applications in which the dielectric (magnetic) properties can be modified by the onset of a magnetic (dielectric) transition or the application of a magnetic (electric) field. The physical mechanisms of the magnetoelectric effect and the origin of ferroelectric order at magnetic transitions have yet to be explored. We discuss multiferroic phenomena in the hexagonal HoMnO 3 and show that the strong magneto-dielectric coupling is intimately related to the lattice strain induced by unusually large spin-phonon correlations.

The magnetic phase diagrams of RMnO3 (R = Er, Yb, Tm, Ho) are investigated up to 14 Tesla via magnetic and dielectric measurements. The stability range of the AFM order below the Neel temperature of the studied RMnO3 extends to far higher magnetic fields than previously assumed. Magnetic irreversibility indicating the presence of a spontaneous magnetic moment is found near 50 K for R=Er, Yb, and Tm. At very low temperatures and low magnetic fields the phase boundary defined by the ordering of the rare earth moments is resolved. The sizable dielectric anomalies observed along all phase boundaries are evidence for strong spin-lattice coupling in the hexagonal RMnO3. In HoMnO3 the strong magnetoelastic distortions are investigated in more detail via magnetostriction experiments up to 14 Tesla. The results are discussed based on existing data on magnetic symmetries and the interactions between the Mn-spins, the rare earth moments, and the lattice., 23 pages, 16 figures, to be published in JMR's Aug. focus issue on multiferroics

are consistent with the model of Allen and Perebeinosin observation of a strong resonance close to the JT gap of2 eV for the Raman phonon peaks at 496 JT antistretching ,611 −1JT stretching , and 655 cm modes, the last one as-signed to an oxygen breathing vibration. The same resonancehas been observed for the main peaks between 1000 and1400 cm

The pressure-temperature phase diagram of multiferroic ${\mathrm{Ni}}_{3}{\mathrm{V}}_{2}{\mathrm{O}}_{8}$ is investigated for hydrostatic pressures up to $2\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$. The stability range of the ferroelectric phase associated with the incommensurate helical spin order is reduced by pressure and ferroelectricity is completely suppressed at the critical pressure of $1.64\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ at $6.2\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. Thermal expansion measurements at ambient pressure show strong steplike anomalies of the lattice parameters associated with the lock-in transition into the commensurate paraelectric phase. The expansion anomalies are highly anisotropic; the related volume change is consistent with the high-pressure phase diagram.

The dielectric constant of multiferroic hexagonal HoMnO_3 exhibits an unprecedented diversity of anomalies at low temperatures (1.8 K< T

The polarized Raman spectra of $\mathrm{Ho}{\mathrm{Mn}}_{2}{\mathrm{O}}_{5}$ and $\mathrm{Tb}{\mathrm{Mn}}_{2}{\mathrm{O}}_{5}$ are reported and discussed. Most of the Raman lines corresponding to $\ensuremath{\Gamma}$-point Raman modes $(13{A}_{g}+13{B}_{1g}+11{B}_{2g}+11{B}_{3g})$ have been observed. The temperature dependence of the $\mathrm{Ho}{\mathrm{Mn}}_{2}{\mathrm{O}}_{5}$ spectra provides no evidence for phonon anomalies associated with magnetic and ferroelectric transitions below $50\phantom{\rule{0.3em}{0ex}}\mathrm{K}$.

Evidence for a strong spin-lattice coupling in multiferroic HoMnO_3 is derived from thermal expansion measurements along a- and c-axis. The magnetoelastic effect results in sizable anomalies of the thermal expansivities at the antiferromagnetic (T_N) and the spin rotation (T_{SR}) transition temperatures as well as in a negative c-axis expansivity below room temperature. The coupling between magnetic orders and dielectric properties below T_N is explained by the lattice strain induced by the magnetoelastic effect. At T_{SR} various physical quantities show discontinuities that are thermodynamically consistent with a first order phase transition.

The critical current density of optimally doped bulk YBCO superconductor has been found to increase with the application of external hydrostatic pressure. This paper reports the transport measurements of the critical current (Ic) of YBCO in the form of a coated conductor (CC) wire under hydrostatic pressure up to 0.24 GPa at 77 K. No noticeable change was observed in both the Ic and n-value of the CC sample in the studied pressure range. Two possible scenarios are discussed to explain the observed effect.

The normal forces of a single sided high temperature superconducting linear synchronous motor (SLSM) have been investigated at 77 K. The SLSM consisted of a superconducting coil made of YBCO coated conductor as the excitation system and a conventional three phase copper wound armature as the stator with a gap of 10 mm in between. Alternating current up to 7.5 A at 10.5 Hz was applied to the armature and direct current up to 40 A to the excitation system. Studies were also made on addition of iron components such as a core and a back plate to the excitation system. The force components adding up to the resulting normal force are discussed. With minimal normal forces compared to the large thrust forces generated, the advantages of such SLSM system for maglev applications are discussed.

Four coils made of YBCO-coated conductor wire were fabricated and connected in series to make up the excitation system of a linear synchronous motor system with a stator made of ordinary copper wire. The electromagnetic forces experienced by the superconducting coils with respect to the stator were studied in the static case. We began with the study of one single coil, followed by two coils connected in series, and finally, four coils in series from which the largest force obtained was of 53.9 N at a gap of 10 mm at 77 K. The critical current, n-value, and inductance were also measured for the coils so that the power dissipation of the field windings can be calculated. This paper also helps us understand whether linear motors with superconducting components are currently economically feasible with present commercially available superconducting wire.

Thrust measurements were performed on a coil made of YBa2Cu3O7-d coated conductor acting as the excitation system of a single-sided linear synchronous motor. The superconducting coil was a single pancake in the shape of a racetrack with 100 turns, the width and effective lengths were 42 mm and 84 mm, respectively. The stator was made of conventional copper wire. At 77 K and a gap of 10 mm, with an operating direct current of I_DC=30 A for the superconducting coil and alternating current of I_AC=9 A for the stator coils, thrust of 24 N was achieved. With addition of an iron core, thrust was increased by 49%. With addition of an iron back plate, thrust was increased by 70%., Comment: 9 pages, 4 figures

We report on the magnetic properties of multiferroic hexagonal HoMnO3 single crystals and polycrystalline samples with micrometer and nanometer particle size. We have studied the in-plane and out-of-plane magnetization of HoMnO3 single crystals under low applied magnetic fields in the temperature range below TNeel = 72 K and observe the bifurcation of zero-field-cooled and field-cooled curves at the Mn spin reorientation transition temperature at 34 K. In addition, the c-axis magnetization shows a ferrimagnetic-like behavior which may relate to the magnetic Ho 3+ and Mn 3+ domain boundary structures and sensitively respond to changes of the magnetic structure such as spin rotations at the phase transitions near 5 and 34 K. We also studied the particles' size dependent magnetic behavior in the HoMnO3 polycrystalline samples and observe the presence of a net magnetic moment at the surface due to the large surface/volume ratio. Below the Ho 3+ ordering temperature of 5 K, magnetization curves as a function of applied magnetic field, in contrast to those for the single crystal, show hysteresis behavior with coercivity, which increases with diminishing particle size.

Thermal expansion measurements were done on single-crystal RMn2O5 (R=Tb,Dy,Ho) along the principal crystallographic axes. Distinctive anomalies were observed in the linear thermal expansivities at critical temperatures marking the onset of long-range antiferromagnetic order (TN1), ferroelectricity (TC1), as well as at temperatures when anomalous changes in the polarization, dielectric constant, and spin wave incommensurability have been previously reported. These observations suggest that the coupling between the magnetic orders and the dielectric properties is mediated by the lattice distortion. In particular, a possible scenario as to how ferroelectricity arises and subsequently is altered as a result of the subtle changes in the highly frustrated magnetic order, is discussed in the light of the strong spin-lattice coupling observed in these materials. Neutron diffraction measurements on HoMn2O5 show a spin reorientation at 23K corresponding to a step-like anomaly in the dielectric constant.

A measurement testing setup of the characteristic properties for high temperature superconducting bearing (HTSB) systems is introduced in this paper. The equipment setup can measure the radial and axial forces, temperature, oscillation and rotary speed of the HTSB simultaneously, so the relation between these properties can be investigated. For example, the decrease of the radial and axial forces, and the increase of the temperature can be measured and analyzed during different rotary speeds of the permanent magnetic rotor. The measurement ranges for the radial and axial force will reach 5 kN and 10 kN. The temperature of the superconductors in HTSB can then be controlled by adjusting the air press inside the dewar which is an easier method compared with a cryocooler.

The anisotropy properties of bulk high-temperature superconductors (HTSCs) are taken into consideration for the application of high-temperature superconducting (HTS) Maglev systems, which are especially based on the different flux-trapping capabilities as well as critical current density, J c, values between the growth section boundary (GSB) and the growth sections (GS) in bulk superconductors. By adjusting the angle between the GSB of bulk HTSCs and the strongest magnetic field position of a permanent magnet guideway (PMG), the levitation force and its relaxation processes are compared at different field-cooling conditions. Experimental results show that the levitation capability and the suppression of levitation force decay can be enhanced by optimizing the GS/GSB alignment of every bulk HTSC above the PMG. Meanwhile, our conclusions may provide references to other HTS maglev systems with small levitation gaps, i.e., superconducting magnetic bearings.