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The pyrochlore iridate has been investigated by means of the electron paramagnetic resonance spectroscopy. A magnetic transition at 20 K is found in addition to the transition at 130 K, which has not been reported previously. The phase transition at , which corresponds to a resistivity transition, is resulted from the long-range spin ordering of ions in all-in/all-out state. However, the magnetic transition at , which is regardless of resistivity transition, is not caused by but ions. Both of the magnetic transitions are irrelevant to the lattice distortion. We suggest that the competition between the enhanced paramagnetism of ions and the f–d interaction should be responsible for the magnetic transition at .

We have studied the magnetic properties of spin-frustrated compound Dy 2 Ti 2− x V x O 7 single crystals. Bulk magnetization data show that ferromagnetic interaction enhances with increasing content of V, resulting from the ferromagnetic interactions between Dy and V ions. It is also found from ac susceptibility that the modestly doped samples ( x ≤0.4) still keep ice state, demonstrating the robustness of spin ice. When the doped concentration increases up to 0.5, more disorder on B site and internal field associated with V 4+ ions would affect the macroscopic ground-state degeneracy and relieve the frustration, leading to the disappearance of spin ice and occurrence of a spin-glass-like transition. The magnetic properties of the system are related to magnetic frustration and local structural disorder.

Magnetic frustrated materials are of great interest for their novel spin-dependent transport properties. We report an anisotropic anomalous Hall effect in the triangular itinerant ferromagnet ${\mathrm{Fe}}_{3}{\mathrm{GeTe}}_{2}$. When the current flows along the $ab$ plane, ${\mathrm{Fe}}_{3}{\mathrm{GeTe}}_{2}$ exhibits the conventional anomalous Hall effect below the Curie temperature ${T}_{c}$, which can be depicted by Karplus--Luttinger theory. On the other hand, the topological Hall effect shows up below ${T}_{c}$ with current along the $c$ axis. The enhancement of Hall resistivity can be attributed to the chiral effect during the spin-flop process.

In this paper, the magnetism of the single-crystal ${\mathrm{Cr}}_{1/3}{\mathrm{NbS}}_{2}$, which exhibits a chiral magnetic soliton lattice (CSL) state, is investigated. The magnetization displays strong magnetic anisotropy when the field is applied perpendicularly and parallel to the $c$ axis in the low-field region ($Hl{H}_{S},\phantom{\rule{0.28em}{0ex}}{H}_{S}$ is the saturation field). The critical exponents of ${\mathrm{Cr}}_{1/3}{\mathrm{NbS}}_{2}$ are obtained as $\ensuremath{\beta}=0.370(4),\phantom{\rule{0.28em}{0ex}}\ensuremath{\gamma}=1.380(2)$, and $\ensuremath{\delta}=4.853(6)$, which are close to the theoretical prediction of the three-dimensional Heisenberg model. Based on the scaling equation and the critical exponents, the $H\ensuremath{-}T$ phase diagram in the vicinity of the phase transition is constructed where two critical points are determined. One is a tricritical point which locates at the intersection across the CSL, the forced ferromagnetic, and the paramagnetic (PM) states. The other one is a critical point situated at the boundaries across the CSL, the helimagnetic, and the PM states.

Controlling functionalities, such as magnetism or ferroelectricity, by means of oxygen vacancies (${V}_{\mathrm{O}}$) is a key issue for the future development of transition-metal oxides. Progress in this field is currently addressed through ${V}_{\mathrm{O}}$ variations and their impact on mainly one order parameter. Here we reveal a mechanism for tuning both magnetism and ferroelectricity simultaneously by using ${V}_{\mathrm{O}}$. Combining experimental and density-functional theory studies of $\mathrm{E}{\mathrm{u}}_{0.5}\mathrm{B}{\mathrm{a}}_{0.5}\mathrm{Ti}{\mathrm{O}}_{3\ensuremath{-}\ensuremath{\delta}}$, we demonstrate that oxygen vacancies create $\mathrm{T}{\mathrm{i}}^{3+}\phantom{\rule{4pt}{0ex}}3{d}^{1}$ defect states, mediating the ferromagnetic coupling between the localized Eu $4{f}^{7}$ spins, and increase an off-center displacement of Ti ions, enhancing the ferroelectric Curie temperature. The dual function of Ti sites also promises a magnetoelectric coupling in the $\mathrm{E}{\mathrm{u}}_{0.5}\mathrm{B}{\mathrm{a}}_{0.5}\mathrm{Ti}{\mathrm{O}}_{3\ensuremath{-}\ensuremath{\delta}}$.

The magnetic structure in the strongly correlated ruthenate $\mathrm{S}{\mathrm{r}}_{4}\mathrm{R}{\mathrm{u}}_{3}{\mathrm{O}}_{10}$ has been debated for a long time and still remains elusive. Here, we perform a systematically planar Hall effect study on a single-crystalline $\mathrm{S}{\mathrm{r}}_{4}\mathrm{R}{\mathrm{u}}_{3}{\mathrm{O}}_{10}$ nanostripe with a thickness of less than 100 nm. Large sharp switching behavior is observed in the planar Hall resistance, unambiguously indicating a strong anisotropic in-plane ferromagnetic order in the nanostripe, which is in contrast to the bulk system. Temperature-dependent evolution of the in-plane magnetism reveals that the in-plane spin order transforms from a single-domain state below a Curie temperature ${T}_{C}$ into a multidomain state below a critical temperature ${T}_{M}$, probably due to the inherent strong spin-orbit coupling driven reconfiguration of spins between the $c$ axis and the $ab$ plane.

We presented the structural, magnetic, and magnetocaloric data for perovskite TmFeO3. XRD revealed distorted orthorhombic structure (Pbnm) for TmFeO3. Spin-reorientation transition was confirmed through magnetic susceptibility. −ΔSM(max) is 13.72 Jkg-1 K−1 at the temperature of 85 K under ΔH = 6 T, with the RCP value of 676 J/kg. −ΔSM(max) and RCP values were increased with the applied field, possibly due to the d-f exchange interactions. The magnetic hysteresis cycles are established for different values of temperatures. These properties make it a potential candidate used for magnetic refrigerants. For magnetic refrigeration application, very large refrigeration capacity is also required along with large entropy change value.

The physical properties of itinerant ferromagnet [Formula: see text]-Co5Ge3 with both strong disorder and spin fluctuations was studied. The dc and ac susceptibility show that both spin fluctuations and disorder dominate the physical properties. In the spin glass phase, with a coexisting ferromagnetic state ([Formula: see text]30 K), both non-Fermi liquid behavior and large exponent of scaling relation of [Formula: see text] are observed and attributed to the spin fluctuations and disorder induced by cobalt defects. Upon the increase of external field, Fermi liquid behavior restores due to the suppression of spin fluctuations and disorder. In addition, a large anomalous Hall coefficient R s is observed. Our results suggest that [Formula: see text]-Co5Ge3 is a typical itinerant ferromagnet to explore the interplay of disorder and spin fluctuations.

The orbitally-induced Peierls phase transition in the Na-doped Cu 1− x Na x Ir 2 S 4 has been investigated. The phase transition temperature on warming T M W increases while that on cooling T M C decreases with x increasing, which means that the phase transition is broadened by the doping of Na ions. However, the average phase transition temperature T M A is not changed. The Raman spectroscopy and X-ray diffraction studies demonstrate that no structural distortion is induced by the doping of Na in Cu 1− x Na x Ir 2 S 4 , which excludes the lattice distortion effect. The tendency to metallic behavior with the doping of Na indicates a hybridization between Na + and surrounding S 2− ions via the outer shell p electrons, which enhances the itinerant characteristic of electrons. It is suggested that the scattering from itinerant electrons and lattice defects may be responsible for the broadening of the orbitally-induced Peierls phase transition.

We have studied the magnetic and dynamical properties of spin-frustrated magnet Dy2Ti2−x FexO7 single crystals. Bulk magnetization data of the heavily Fe doped samples give a negative Curie–Weiss temperature, probably suggesting the existence of short-range antiferromagnetic interaction in Fe-doped samples. Dynamical analyses show that the doped system still freezes into an ice-like state but it is more dynamical than that in pure spin ice Dy2Ti2O7. Furthermore, the dynamic freezing of the spins is suppressed to lower temperatures, which is caused by the Dy-Fe spin interactions and the altered crystalline electric field. It is also found that the coordination number of Fe decreases at high doping level (x=0.15), leading to the change of the spin state of Fe3+.

Critical behaviors of the half-doped perovskite cobaltites Pr0.5Sr0.5 CoO 3 - Δ ( Δ = 0 and ∼0.16) are investigated around the critical temperatures by bulk magnetization study, where the critical exponents (β, γ and δ) are obtained. These critical exponents fulfill the Widom scaling law δ = 1 + γ β - 1 , indicating self-consistency and reliability of the obtained results. With the critical exponents, M – T – H curves collapse onto two independent universal branches below and above the critical temperatures. The critical exponents of the oxygen-nonstoichiometric Pr0.5Sr0.5 CoO 3 - Δ accord with the mean-field model exactly. However, for the oxygen-stoichiometric Pr 0.5 Sr 0.5 CoO 3 , β deviates to the theoretical prediction of three-dimensional Heisenberg model while γ and δ are close to that of mean-field model. These results indicate long-range ferromagnetic coupling in Pr0.5Sr0.5CoO3−Δ ( Δ = 0 and ∼0.16), which cannot be explained by the nearest-neighbor interaction proposed for the double-exchange mechanism. Instead, the collective effect of p - d hybridization and RKKY interaction of Pr 3 + f-electrons with the conduction electrons is suggested to be responsible for the long-range interaction. In addition, the discrepancy of β in the oxygen-stoichiometric Pr0.5Sr0.5CoO3 may be due to a short-range interaction corresponding to the extra crystalline phases in the oxygen-stoichiometric sample.

We employed x-ray diffractometer, electron microscope and magnetometer to study the structure and magnetic properties of polycrystalline MnSi. Pure and homogeneous MnSi phase can be obtained in a certain composition range. Intriguingly, our magnetic measurements indicate that the polycrystalline MnSi shows typical magnetic phase transitions as single crystals. The magnetic transformations between helical, conical, skyrmion and field-polarized states can be well detected in the field-dependent susceptibility curves. The similar magnetic behaviors observed for polycrystalline and single crystals make magnetometry an effective and straightforward route to identify skyrmions, especially useful for the materials that are hard to prepare single crystals or epitaxial thin films.

The temperature dependence of magnetization of Ba3Cr2O8 was investigated under an applied hydrostatic pressure of 0 and 1 GPa and analyzed based on the Curie–Weiss model and the Bleaney–Bowers model. Experimental results show that while the intradimer coupling J0 is hardly affected the interdimer interaction J ' is significantly weakened upon the application of pressure. The underlying magnetic behavior is presumably related to the subtle change of the lattice induced by the applied pressure.

In the present paper, we report the bulk magnetization, electron-spin-resonance spectra and transport properties of Y2Ir2O7. It is found that Y2Ir2O7 exhibits a magnetic transition at Tc=150 K and coexistence of antiferromagnetic and ferromagnetic component due to geometrical frustration. The antiferromagnetic order is due to Ir–O–Ir superexchange interactions and the ferromagnetic component is caused by canting of the moments from the antiferromagnetic state. The behavior of spin dynamics confirms that antiferromagnetic ordering with all-in/all-out structure is responsible for the existence of ferromagnetic component. The resistivity reveals that this compound is a semiconductor and the variable-range hopping process dominates the transport mechanism.

The magnetic order and dynamical properties of spin-frustrated magnet Dy 2− x Yb x Ti 2 O 7 single crystals have been studied by dc and ac susceptibility measurements. It is found that the substitution of the Dy 3+ by the Yb 3+ in Dy 2 Ti 2 O 7 relaxes ferromagnetic coupling. In low Yb 3+ doping samples, a spin freezing peak at T f (T f T s associated with Dy 3+ are observed. With increasing Yb 3+ doping, a new peak marked by T ⁎ associated with Yb 3+ appears. We suggest that T ⁎ originates from the thermally activated spin fluctuations of Yb 3+ . It is also found that the relaxation process for T s becomes both thermally activated and quantum tunneled in x ≥1.0 samples. The low-temperature dynamical behaviors of Dy 2− x Yb x Ti 2 O 7 are dominated by the Dy–Yb spin interactions and the altered crystalline electric field. Moreover, crystal field-phonon coupling may contribute to the spin dynamic properties.

In this work, we perform a systematic study of the lattice dynamics of IrTe using temperature dependence of X-ray diffraction experiment. It is found that the lattice structural symmetry of IrTe changes from trigonal (space group ) into monoclinic () below the phase transition temperature (). Remarkably, experimental results show that the trigonal cell still insists below , which coexists intrinsically with the monoclinic cell. After the phase transition, the proportion of the monoclinic cell almost remains unchanged. The structure phase transition temperatures determined from cooling and warming are 240 K and 265 K, respectively. Moreover, the superlattice phase is found with 13.5 , which is suggested to be caused by the destabilization of polymeric Te–Te bonds.

We have investigated the critical behavior of Mn 3 CuN in the ferromagnetic (FM) to paramagnetic (PM) transition. Critical behavior of Mn 3 CuN can be divided into two stages around Curie temperature ( T C ): i) Z I ( T > T C ) and ii) Z II ( T T C ). By using various methods, including modified Arrott plot, Kouvel–Fisher (KF) method, and critical isotherm analysis, reliable critical exponents β , γ and δ are approached. With these critical exponents, magnetization–field–temperature ( M–H–T ) data below and above T C collapse into two universal branches in the asymptotic critical region following the scaling equation. It was found that in Z I mean-field model occupies a predominate position, while for Z II , J ( r )∼ r −4.8 lies between the theoretical values of 3D Heisenberg model and the mean-field model, indicating that the competition between Mn–Mn and Mn–N bonds should be responsible for the exchange interaction.

We grew pure 1T/2H-TaS2 single crystals via the chemical vapor transport (CVT) method and introduced defects into the samples by quenching. We systematically investigated the influence of defects on charge–density–wave (CDW) and superconductivity (SC) in 1T and 2H-TaS2. The defects can induce SC to 1T-TaS2 system, and inhibit the commensurate CDW (CCDW) and Mott insulator phase, the superconducting transition temperature ( T c Onset ) is about 2.5 K and the zero resistivity temperature ( T c zero ) is about 0.7 K. For 2H-TaS2, the defects nearly have no effect on CDW, while T c Onset is increased to about 2.7 K. The magnetization hysteresis loops show typical type-II superconductor behaviors for both 1T and 2H-TaS2 systems.

In this work, we successfully synthesize the single crystal Cr11Ge19. The magnetism of the noncentrosymmetric Cr11Ge19 with itinerant ferromagnetic ground state is thoroughly investigated on the single crystal. Based on the variation measurements including the angular rotation, temperature, and magnetic field dependence of magnetization, we find that this material exhibits strong magnetic anisotropy along the c-axis. To clearly reveal the magnetic interactions, the critical behavior is studied using the modified Arrott plot, the Kouvel-Fisher method, and the critical isotherm technique. Combining these different methods, three main critical exponents (β, γ, and δ) are obtained. The critical exponent β is close to the theoretical prediction of a three-dimensional XY model with spin-dimensionality n = 2, indicating two-dimensional magnetic coupling. Meanwhile, the critical exponent γ suggests that the magnetic interaction is of long-range type with magnetic exchange distance decaying as J(r) ≈ r−4.61. We propose that the ferromagnetic ground state of Cr11Ge19 is formed by the polarized magnetic moments along the c-axis, while the long-range magnetic coupling is established within the ab plane.

$\mathrm{R}{\mathrm{h}}_{2}\mathrm{M}{\mathrm{o}}_{3}\mathrm{N}$, with a noncentrosymmetric $\ensuremath{\beta}$-manganese structure, has been found to be superconducting with critical temperature ${T}_{c}\ensuremath{\approx}4.3\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. Magnetic field dependence of resistivity, magnetization, and specific heat measurements show that its upper critical field of ${\ensuremath{\mu}}_{0}{H}_{c2}^{*}\phantom{\rule{4pt}{0ex}}\ensuremath{\sim}7.41\phantom{\rule{0.16em}{0ex}}\mathrm{T}$ comes close to, but does not exceed, the Pauli paramagnetic limit and that the $2\mathrm{\ensuremath{\Delta}}/{k}_{\mathrm{B}}{T}_{c}$ value of about 3.62 is in accordance with a conventional $s$-wave superconductor. Andreev reflection spectroscopy measurements using both normal metal and half-metal show conclusively $s$-wave pairing with an isotropic gap.

Mono-arsenide CrAs, endures a helical anti-ferromagnetic order transition at ∼265 K under ambient pressure. Recently, pressure-induced-superconductivity was discovered vicinity to the helical anti-ferromagnetic order in CrAs [Wei Wu et al., Nature Communications 5, 5508 (2014).]. However, the size of crystal grown via tin flux method is as small as 1 mm in longest dimension. In this work, we report the single crystal growth of CrAs with size of 1 × 5 × 1 mm3 via chemical vapor transport method and its physical properties.

The search for nontrivial superconductivity in novel quantum materials is currently a most attractive topic in condensed matter physics and material science. The experimental studies have progressed quickly over the past couple of years. In this article, we report systematic studies of superconductivity in Au2Pb single crystals. The bulk superconductivity (onset transition temperature, Tconset=1.3 K) of Au2Pb is characterised by both transport and diamagnetic measurements, where the upper critical field Hc2 shows unusual quasi-linear temperature dependence. The superconducting gap is revealed by point-contact measurement with gold tip. However, when using tungsten (W) tip, which is much harder, the superconducting gap probed is largely enhanced as demonstrated by the increases of both Tconset and upper critical field (Hc2). This can be interpreted as a result of increase in density of states under external anisotropic stress imposed by the tip, as revealed by first-principles calculations. Furthermore, novel phase winding of the pseudospin texture along k-space loops around the Fermi energy is uncovered from the calculations, indicating that the observed superconductivity in Au2Pb may have nontrivial topology. Researchers in China have uncovered evidence for a new type of superconductivity in an old alloy. Jian Wang from Peking University and co-workers measured the superconducting properties of gold-lead (Au2Pb) and observed what could be an unusual effect known as topological superconductivity–superconductivity that arises due to a particular electronic structure. The researchers measured the low temperature resistivity of a single crystal of Au2Pb and confirmed that it is a superconductor. Simulations indicated that its superconductivity arises from its electronic structure, which has a nontrivial topological arrangement. Superconducting materials enable ultrasensitive sensors of magnetic fields and powerful magnets, but they usually exhibit their unusual properties only at low temperatures. Materials that exhibit superconductivity in new and unusual ways are of interest because they may open the door for ways to circumvent these limitations.

In this paper, we present the investigations of electron paramagnetic resonance on perovskite manganite Pr0.5Sr0.5MnO3 and Ga-doped Pr0.5Sr0.5Mn0.95Ga0.05O3. The temperature dependent paramagnetic resonance spectra parameters (effective g-factor, peak-to-peak linewidth ΔH pp and double integrated intensities) have been used to study the paramagnetic spin correlations and spin dynamics. The gradual increase of effective g-factor is attributed to the presence of orbital ordering above T C. The model fittings of temperature dependent double integrated intensities reveal Arrhenius law is appropriate for describing Pr0.5Sr0.5Mn0.95Ga0.05O3 instead of Pr0.5Sr0.5MnO3 system. As for Pr0.5Sr0.5MnO3, the broadening of linewidth with the temperature increase origins from the contribution of small polaron hopping in the PM regime. However, as for Pr0.5Sr0.5Mn0.95Ga0.05O3, the broadening of EPR linewidth can be understood with the spin-lattice relaxation mechanism.

The effects of As doping on the superconductivity and magnetism in the Tl0.4K0.4Fe2−y Se2 superconductor are studied. We find that the As doping does not significantly change the occupancy at the Fe-site, meaning a certain amount of Fe ions changes its valence from 2+ to 3+. The superconductivity is gradually suppressed with increasing As doping. The magnetic measurements suggest that though the As doping does not destroy the antiferromagnetic order in the system, it induces an increase in the staggered magnetic moment. These results suggest that the Tl0.4K0.4Fe2−y Se2 system is a system with intrinsic phase separation. The change in the valence state of Fe could be a possible reason for the suppression of superconductivity.

Electron paramagnetic resonance studies have been performed on the perovskite manganite Pr0.55Sr0.45MnO3. The various spectrum parameters including line width, effective g-value and double-integrated intensities have been analyzed in detail. The changes of g-value and linewidth are indicative of the presence of strong spin–lattice interaction in the paramagnetic regime. The lattice distortion causes the appearance of localized carriers and the formation of a small polaron. Therefore, the large activation energy obtained from two different methods implies that a strong spin–lattice correlation exists in Pr0.55Sr0.45MnO3.

The substitution of Ga for Mn in manganite Nd0.6Dy0.1Sr0.3MnO3 with a ferromagnetic (FM) ground state has been performed to study the influence of the Mn-sublattice magnetic ordering on the magnetic rare-earth sublattice. It is found that the substitution of Mn3+ with Ga3+ ions results in a sharp decrease of TC, reflecting the reduction of the double-exchange interactions strength JMn–Mn. At the same time, a depinning effect of the rare-earth magnetic moment has been observed. This behavior unambiguously proves that the exchange interaction between Mn and rare-earth ions JMn–R strongly influences the rare-earth magnetic ordering at temperatures below TC and stabilizes the rare-earth magnetic ground state.

Transport and magnetic properties of the CuIr2−xAlxS4 system have been investigated. It is found that the Peierls-like phase transition is suppressed with the substitution of Al. In addition, the resistivity under strong magnetic field shows that the Peierls-like phase transition is very steady to the external field. The study of magnetization reveals that the density of states at the Fermi level [ N ( E F ) ] is not influenced by the doping of Al, while the localization length is decreased with the increase of Al. Theoretically, we find that the upturn of the magnetization at low temperatures is produced by paramagnetic clusters, which are formed by several moments captured by defects. Moreover, the increase of Al content just increases the number of capture centers, but does not affect the magnetic moment of a single paramagnetic cluster.

In this paper, we have studied the magnetic and magnetocaloric properties of the perovskite manganite Pr 0.55 Sr 0.45 MnO 3 . It shows a sharp paramagnetic–ferromagnetic phase transition at 291 K and possesses a moderate magnetic entropy change near room temperature. In addition, a large relative cooling power (143.64 J/kg) and a wide temperature range (84 K) have been found in this material. Compare with the Landau model, we find that the itinerant electrons mainly contribute the larger magnetic entropy change at paramagnetic region.

The epitaxial thin films of Ge0.96−xBixFe0.04Te are deposited on BaF2 substrates by using pulsed laser deposition technique. The thin films with three different compositions i.e. Ge0.8Bi0.2Te, Ge0.76Bi0.2Fe0.04Te, and Ge0.64Bi0.32Fe0.04Te are prepared in this wok. Their high-quality epitaxy and crystallinity are confirmed by X-ray diffraction and atomic force microscopy. According to the measurements of Hall effect variation, we find that each of all curves exhibits a negative slope for the different films as the temperature varies from low temperature to room temperature, indicating that Ge0.96−xBixFe0.04Te films are n-type material because the substitution of Bi for Ge makes the carriers change from holes into electrons. Temperature dependence of resistivity confirms that the electronic transport behavior for each of Ge0.96−xBixFe0.04Te thin films exhibits a typical semiconductor characteristic. From the measurements of temperature dependence of electronic transport under various external magnetic fields, we find that the Ge0.64Bi0.32Fe0.04Te thin film shows some magnetoresistive effect while other composition films do not possess such a property. Based on the linear fitting of temperature dependence of magnetic susceptibility in high temperature and low temperature region, the magnetic property of Ge0.64Bi0.32Fe0.04Te thin film changes from 253 K. Together with the study of magnetic susceptibility curve in the paramagnetic region, the Curie-Weiss temperature is determined to be 102 K. At a low temperature of 10.0 K, we observe an obvious ferromagnetic hystersis loop in Ge0.64Bi0.32Fe0.04Te instead of in Ge0.76Bi0.2Fe0.04Te thin film. These results imply that the increase of Bi dopant is main reason for the establishment of ferromagnetic ordering state. The carrier concentration increases and thus promotes the carriers transporting the Ruderman-Kittel-Kasuya-Yoshida interaction, thereby leading to the separated Fe ions producing the magnetic interaction and forming an n-type diluted magnetic semiconductor.

Structure, spectrum, magnetic, and transport properties of the compounds Cu1−xLixCr2Se4 ( x = 0 – 0.7 ) have been experimentally investigated. X-ray photoelectron spectroscopy spectra (XPS) suggest dominant monovalent Cu+ in the samples. With Li+ substitution for Cu+, the ground state changes from ferromagnetic metal to ferromagnetic insulator due to the suppression of the holes in a ligand Se p –Cu d orbitals, leading to the decrease of the saturation moment M s . Both the spectrum and the magnetic results suggest that Lotgering’s model of Cu+[Cr3+]2Se4 is relevant. There is an inner compressive strain in the system, which results in thermal hysteresis in M ( T ) and ρ ( T ) curves.

The magnetic behavior and electronic transport in the half-doped manganite Nd0.5Ca0.25Sr0.25MnO3 have been investigated. The critical exponents are studied by using isothermal magnetization methods. The results show that the paramagnetic–ferromagnetic transition is second order and the magnetic interaction is satisfied with the prediction of three-dimensional Heisenberg model. The electronic transport belongs to the percolation mechanism. These findings demonstrate that the critical behavior of the magnetic transition and conductivity for manganites are related to Mn-site ordering degree.

a b s t r a c t The magnetic entropy around the paramagnetic-ferromagnetic (PM-FM) phase transition temperature TC has been investigated for chromium based spinel CdCr2Se4. It is found that magnetic entropy changes are generated by the spin-lattice coupling, which can be easily modulated by the external magnetic field. The electron paramagnetic resonance (EPR) study proves the existence of the spin-lattice coupling above TC , and reveals the stronger coupling at TC . In addition, the variation of the micro-structure due to the spin-lattice interaction has been observed around TC from the measurement of the low-temperature X- ray diffraction.

In this paper, we investigated the electrical and magnetic properties of electron-doped manganite Y 0.4Ca0.6MnO3 with a relatively small average cationic radius 〈 r A 〉 . The small 〈 r A 〉 of the present system results in a short-range antiferromagnetic charge-ordering (AFM-CO) state in the manganite. With the decrease of temperature, a ferromagnetic super-exchange interaction begins to establish itself between the remaining disordered Mn ions after the formation of the short-range CO state. Then, a reentrant cluster-glass state originates from the frustration between the FM order in the clusters and the AFM interactions present in the background matrix.

In this paper, we have investigated the magnetic properties of spinel sulphide materials Cu 1 − x Ag x Ir 2 S 4 ( 0 ≤ x ≤ 0.15 ) . Based on the measurement of magnetization and specific heat, the weak remnant ferromagnetism is found in this system. The remnant ferromagnetism, which coexists with paramagnetism and diamagnetism, is enhanced with the increase of Ag content. Theoretical calculation in magnetization and specific heat also supports the present experimental observation. The remnant ferromagnetism observed here may be related to either non-dimerized Ir 4 + ions or defects in this system.

The lattice dynamics in the CuIr2S4 system have been investigated through Raman spectroscopy and the induced-pressure effect. Four Raman active modes are observed experimentally. Upon cooling, these Raman spectra undergo changes due to the Peierls-like phase transition. In addition, the substitution of Ag for Cu affects the amplitude of the Raman spectra while keeping their wave number unchanged. Furthermore, the positive and negative pressure effects are induced by shrinking and expanding the lattice. It is suggested that the pressure effect is an effective proof of the orbital-induced Peierls state mechanism.

We report electrical transport and anisotropic magnetic properties of Mn-intercalated 2H-TaS2, a layered transition-metal dichalcogenide with a hexagonal structure. The single crystal MnxTaS2 with x = 1/3 exhibits a transition from paramagnetism to ferromagnetism near 70 K, below which both the magnetoresistance and magnetization properties present strong anisotropic behavior. Its anisotropic magnetoresistance effect and in-plane soft ferromagnetic property suggests that this layered material would be a good candidate for exploring the physics of two-dimensional ferromagnetism.

In the present work, the magnetic entropy change of the half-doped Nd0.5Ca0.25Sr0.25MnO3 manganite has been investigated. The measurement of isothermal magnetization around Curie temperature reveals the maximum isothermal magnetic entropy change of 1.85 and 0.77 J/kg K for Δ H = 3.0 and 1.0 T magnetic field variation, respectively. In addition, from the data of heat capacity, we find the adiabatic temperature change of 0.88 K for a magnetic field variation of 3.0 T. Though only a moderate magnetic entropy change and a small adiabatic temperature change were obtained, a considerable large relative cooling power (140 J/kg as Δ H = 3.0 T ) and a wide temperature range (74 K as Δ H = 3.0 T ) were found in this sample, this ensure it to be a promising candidate for the actual magnetic refrigerant materials.

We perform oxygen doping experiments in the CaFeAsF and CaFe0.88Co0.12AsF compounds. In the parent compound CaFeAsF, partial replacement of F by O leads to an increase of resistivity and a weakening of spin-density wave transition, indicating that the out-of-plane disorder strongly affects the electronic and magnetic properties of the system. In the CaFe0.88Co0.12AsF1−xOx system, the doping of oxygen leads to the suppression of superconductivity, reflecting the importance of Ca–F layer disorder in this system.

In this paper, the magnetocaloric effect of perovskite manganite Nd 0.6 La 0.1 Sr 0.3 MnO 3 has been investigated. From the measurement of isothermal magnetization around the Curie temperature, we have calculated the maximum isothermal magnetic entropy change as 3.14 J/kg K for the 1.5 T magnetic field variation. Furthermore, a large relative cooling power of 45 J/kg has been determined, which makes Nd 0.6 La 0.1 Sr 0.3 MnO 3 attractive candidate materials for magnetic refrigeration.

The magnetic properties of Y 0.35Ln0.05Ca0.6MnO3 (Ln = La, Pr, Nd, Sm, Gd, Dy) have been investigated thoroughly. The small average cationic radius 〈 r A 〉 of the present system results in a short-range antiferromagnetic charge-ordering (AFM-CO) state in the manganites. With the decrease of temperature, a super-exchange interaction begins to establish itself between the remaining disordered Mn ions after the formation of the short-range CO state. Then, the reentrant cluster-glass state originates from the frustration between the FM order in the clusters and the AFM interactions present in the background matrix. However, the large magnetic moments of Gd3+ and Dy3+ ions apply an internal magnetic field on the Mn3+ and Mn4+ ions, which results in the suppression of the cluster-glass state.

The magnetic properties of Nd0.6Ln0.1Sr0.3MnO3 compositions (Ln = La, Pr, Gd, Dy) have been investigated thoroughly. The effect of 〈 r A 〉 is considered to be profound on the PM–FM phase transition in the manganites. The experiment results indicate that T C decreases with Ln changing from La to Gd due to the decreases of 〈 r A 〉 . The abnormal increase of T C in Dy-composition with the smallest 〈 r A 〉 and largest σ 2 is attributed to the large magnetic moment of Dy3+ ions. The rapid increase of magnetization below 30 K indicates directly the magnetic ordering of rare earth ions at A-site.

Charge density wave (CDW), the periodic modulation of the electronic charge density, will open a gap on the Fermi surface that commonly leads to decreased or vanishing conductivity. On the other hand superconductivity, a commonly believed competing order, features a Fermi surface gap that results in infinite conductivity. Here we report that superconductivity emerges upon Se doping in CDW conductor ZrTe$_{3}$ when the long range CDW order is gradually suppressed. Superconducting critical temperature $T_c(x)$ in ZrTe$_{3-x}$Se$_x$ (${0\leq}x\leq0.1$) increases up to 4 K plateau for $0.04$$\leq$$x$$\leq$$0.07$. Further increase in Se content results in diminishing $T_{c}$ and filametary superconductivity. The CDW modes from Raman spectra are observed in $x$ = 0.04 and 0.1 crystals, where signature of ZrTe$_{3}$ CDW order in resistivity vanishes. The electronic-scattering for high $T_{c}$ crystals is dominated by local CDW fluctuations at high temperures, the resistivity is linear up to highest measured $T=300K$ and contributes to substantial in-plane anisotropy., Comment: 15 pages, 4 figures

Mono-arsenide CrAs, endures a helical anti-ferromagnetic order transition at~ 265 K under ambient pressure. Recently, pressure-induced-superconductivity was discovered vicinity to the helical anti-ferromagnetic order in CrAs[Wei Wu et al., Nature Communications 5, 5508 (2014).]. However, the size of crystal grown via tin flux method is as small as 1 mm in longest dimension. In this work, we report the single crystal growth of CrAs with size of 1 * 5 * 1 mm3 via chemical vapor transport method and its physical properties., Comment: 9 pages, 3 figures

The electrical and magnetic properties of highly doped manganite Gd0.4Ca0.6MnO3 with a relatively small 〈 r A 〉 have been investigated thoroughly. Through the M – T , M – H , and ESR measurements it is found that the magnetization in M – T curve originates from the paramagnetic contribution of disordered Mn ions at B-site and Gd3+ ions at A-site. The peculiar behavior of M – T curve below TCO originates from the remaining spin disordered Mn ions after the formation of charge-ordering phase in the manganite, and the AFM charge-ordering state is supposed to be a local short-range ordering state.

Quantum spin liquid (QSL) is a novel state of matter which refuses the conventional spin freezing even at 0 K. Experimentally searching for the structurally perfect candidates is a big challenge in condensed matter physics. Here we report the successful synthesis of a new spin-1/2 triangular antiferromagnet YbMgGaO$_4$ with R$\bar{3}$m symmetry. The compound with an ideal two-dimensional and spatial isotropic magnetic triangular-lattice has no site-mixing magnetic defects and no antisymmetric Dzyaloshinsky-Moriya (DM) interactions. No spin freezing down to 60 mK (despite $\Theta$$_w$ $\sim$ -4 K), the low-T power-law temperature dependence of heat capacity and nonzero susceptibility suggest that YbMgGaO$_4$ is a promising gapless ($\leq$ $|$$\Theta$$_w$$|$/100) QSL candidate. The residual spin entropy, which is accurately determined with a non-magnetic reference LuMgGaO$_4$, approaches zero ($, Comment: 28 pages including supplementary materials, 4 figures, 33 references