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With Fermat Principle, that is, the most fundamental principle in geometric optics, it is easy to obtain the three laws of geometric optics as well as the paraxial refraction and catoptric imaging laws. Making use of the principle and a simple mathematical relation, this paper expounds and derives the rectilinear propagation law of rays in the homogeneous medium, the optical reflection and refraction laws as well as the spherical reflection and refraction laws under the paraxial condition. Ulteriorly, with given character rules, the spherical dioptric and catoptric imaging formulas can be generalized into a unified formula separately. The elaboration and derivation in this paper reflect the simplicity of physics and reduce the error probability of complex trigonometric function operation, thus making it more easy for high school students or junior undergraduate and junior college students to accept and understand.

We report the synthesis and electrical resistivity of Zr (Cu, Fe)Se2−δ single crystals with layered hexagonal structure (space group P-3M1, No. 164). Se vacancies are found existed in all pristine samples. Adding Fe into the raw materials results in substitution of Zr and the lattice parameters are found almost unaffected while that with Cu results in intercalation of the van der Waals gap and the lattice parameters are expanded essentially. All compounds display semiconducting behavior, i.e. negative temperature dependence, and the activation energy (Δ) estimated from thermal activation model are in the range of 50–200 meV. We also observe spin-glass-like behavior in the Fe-containing samples.

The magnetic properties of CsCo2Se2, possessing a ThCr2Si2-structure, are systematically studied by using specific heat, resistivity, and torque measurements. Our results reveal that CsCo2Se2 undergoes a paramagnetic state to antiferromagnetic order at T N ≈ 80 K at zero magnetic field. The T N is nearly independent of the external magnetic field for H ‖ c-axis, and can be suppressed for H ‖ ab-plane below 4 T, above which spin-flop phase transition sets in. At 2 K, the magnetoresistance has a small value of 2.3% for H ‖ c-axis while goes up to 60% for H ‖ ab-plane at 9 T. A hump-like behavior in resistivity was discovered, which was ascribed to a field-induced spin-flop phase transition. The magnetoresistance results suggest that a crossover of spin-flop phase transition occurs at low temperatures in the field range of 2–4 T for H ‖ ab-plane. Furthermore, the magnetic torque results reveal a novel ordered Co spin structure at low temperatures under 6 T for H ‖ ab-plane. Finally, we summarize the magnetic phase diagram of CsCo2Se2 based on resistivity and torque results.

The critical behavior of ferromagnetic transition is investigated by bulk magnetization measurements for La0.85Co1.68As2 crystal with a ThCr2Si2-type structure, grown by using NaAs as a flux, in which the vacancies on the both La and Co sites exist. The critical exponents [ β = 0.388(3), γ = 1.44(2) and δ = 4.855(9)] with Curie temperature T c = 99.4 K are obtained, whose self-consistency and reliability are verified by the Widom scaling law and the scaling equation. The critical exponents of ferromagnetic transition occurring in La0.85Co1.68As2 belong to the three-dimensional (3D) Heisenberg model, and suggest that the magnetic interaction decays as J ( r ) ∼ r − 4 . 975 with a short range coupling. These results provide helpful information for understanding the mechanism of ferromagnetism emerging in La0.85Co1.68As2 compound.

we have reported the synthesis, electrical resistivity ρ (T), Hall coefficient (RH) and magnetoresistance (MR) of Bi2O2Se single crystals with layered tetragonal structure (space group I4/mmm). The lattice parameters obtained after Rietveld refinement are a = b = 3.897 A, c = 12.237 A, respectively. ρ (T) and RH measured in the temperature range from 2 K to 300 K show high carrier concentration extrinsic semiconductor behavior. At higher temperatures (130–300 K), the resistivity is dominated by phonon scattering mechanism, as manifested by ρ (T) ∝ T1.5. The magnetic field dependence of resistivity is positive in the whole temperature range. The MR at 2 K increase monotonically with magnetic field and manifest very weak saturate trend up to 9 T where it reaches its maximum value with Δ ρ xx / ρ xx ≈ 100%.

We have investigated the X-ray diffraction (XRD) spectra, magnetic susceptibility χ(T) and electrical resistivity with and without magnetic field H, ρ(H, T), of an arc melted MoCx alloy. XRD data suggest that the pristine sample is not in the homogeneity range. Magnetic and electrical transport measurements indicate consistently that the sample become superconducting at around Tc ∼ 5.8 K. Further, the upper critical field (Hc2) is estimated to be 1.6 ± 0.1 Tesla by using empirical formulas.

The so-called Dirac materials such as graphene and topological insulators are a new class of matter different from conventional metals and (doped) semiconductors. Superconductivity induced by doing or applying pressure in these systems may be unconventional, or host mysterious Majorana fermions. Here, we report a successfully observation of pressure-induced superconductivity in an antiferromagnetic Dirac material BaMnBi2 with T c of ~4 K at 2.6 GPa. Both the higher upper critical field, μ0H c2(0) ~ 7 Tesla, and the measured current independent of T c precludes that superconductivity is ascribed to the Bi impurity. The similarity in ρ ab (B) linear behavior at high magnetic fields measured at 2 K both at ambient pressure (non-superconductivity) and 2.6 GPa (superconductivity, but at the normal state), as well as the smooth and similar change of resistivity with pressure measured at 7 K and 300 K in zero field, suggests that there may be no structure transition occurred below 2.6 GPa, and superconductivity observed here may emerge in the same phase with Dirac fermions. Our findings imply that BaMnBi2 may provide another platform for studying SC mechanism in the system with Dirac fermions.

We report the critical current density Jc and the vortex dynamics in phase-separated Tl0.58Rb0.42Fe1.72Se2 crystals by performing magnetization measurements. Structural investigation reveals micro- and nanoscopic phase separation between 122 (superconducting) and 245 (not superconducting) phases. Micrometric phase separation refers to 245 islands with typical diameters of 2 µm embedded in a multiply-connected 122 superconducting network. Nanoscopic phase separation refers to 245 nanoprecipitates embedded in the 122 superconducting paths. The 245 nanoprecipitates with size comparable to the coherence length produce strong vortex pinning. It was observed that the temperature dependence of the flux creep rate presents a peak at intermediate temperatures and magnetic fields lower than 0.5 T. The peak is systematically suppressed as the magnetic field is increased, and it could be related with relaxation generated by double-kink excitations. Double-kinks are low-energy depinning excitations usually associated with strong pinning produced by correlated disorder. Fil: Haberkorn, Nestor Fabian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Troiani, Horacio Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Condo, Adriana Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Wang, Hangdong. Zhejiang University; China. Hangzhou Normal University; China Fil: Mao, Qianhui. Zhejiang University; China Fil: Fang, Minghu. Zhejiang University; China. Collaborative Innovation Center of Advanced Microstructures; China

In this article, the structure, transport and magnetic properties were studied in details for EuMn

To better suit the bandgap of solar cell, we proposed a novel theoretical model of solar thermophotovoltaic system, which consists of a concentrator, a surface-textured absorber, an emitter, a photovoltaic cell, and a downconversion layer. Two configurations of rear and front down converters are proposed to enhance the performance of the solar thermophotovoltaic system. The corresponding expressions of particle and heat fluxes are derived. Based on balance equations of particle and energy, the temperatures of emitter and solar cell, and the voltages of down converter are determined. In addition, the influences of solar concentration ratio, geometrical factor, and refractive indexes of emitter and solar cell are considered. Moreover, the operating voltage of solar cell, the areas of emitter and solar cell, and the bandgap of solar cell are optimized at the maximum efficiency condition. The results show that the existence of down converter can efficiently enhance the performance of the solar thermophotovoltaic system, and the proposed configurations can provide theoretical guidance for efficient solar energy harvesting.

In this paper, 133Cs nuclear magnetic resonance (NMR) measurements have been performed to investigate the magnetic properties of an A-type antiferromagnet CsCo 2 Se 2 . The field-sweeping NMR spectra become broadened mainly due to the internal magnetic field attributed to antiferromagnetic ordering. Both T -dependence of Knight shift 133 K and T divided spin-lattice relaxation rate 1/ T 1 T provide clear evidences for the antiferromagnetic transition at ∼ 70 K. 1/ T 1 T exhibits a Curie–Weiss T -dependence down to 80 K, suggesting the development of antiferromagnetic spin fluctuations with decreasing temperature. The linear-relationship between T 1 T - T suggests that antiferromagnetic spin fluctuations are two-dimensional in the paramagnetic state.

The reactivity and fate of parabens during chlorination were investigated in this work. Chlorination kinetics of methylparaben (MeP), ethylparaben (EtP), propylparaben (PrP), and butylparaben (BuP) were studied in the pH range of 4.0 to 11.0 at 25 ± 1 °C. Apparent rate constants (k app) of 9.65 × 10−3 M-0.614·s−1, 1.77 × 10−2 M-1.019·s−1, 2.98 × 10−2 M-0.851·s−1, and 1.76 × 10−2 M-0.860·s−1 for MeP, EtP, PrP, and BuP, respectively, were obtained at pH 7.0. The rate constants depended on the solution pH, temperature, and NH4 + concentration. The maximum k app was obtained at pH 8.0, and the minimum value was obtained at pH 11.0. The reaction rate constants increased with increasing temperature. When NH4 + was added to the solution, the reaction of parabens was inhibited due to the rapid formation of chloramines. Two main transformation products, 3-chloro-parabens and 3,5-dichloro-parabens, were identified by GC-MS and LCMS-IT-TOF, and a reaction pathway was proposed. Dichlorinated parabens accumulated in solution, which is a threat to human health and the aqueous environment.

This study was undertaken to develop an extraction method for seven acidic pharmaceuticals and five steroidal estrogens from wastewater, treated wastewater and sludge samples. The temperature and time of sample derivatization using N,O-bis(trimethylsilyl)trifluoroacetamide was optimized. Our results show that pretreatment combined with solid phase extraction (SPE) for wastewater samples (using an ENVI-C18 cartridge) and liquid-solid extraction combined with SPE (using an HLB cartridge) for sludge samples increased the analytical efficiency for acidic pharmaceuticals and estrogenic hormones using gas chromatography-mass spectrometry (GC-MS). The derivatization conditions were optimized at 40°C for 2 h. In addition, the derivatized samples were stable at ambient temperature. The new method was validated and applied to the analysis of real wastewater and discharged sludge samples from a local wastewater treatment plant. Except for 17α-ethinylestradiol, all acidic pharmaceuticals and estrogens were detected in the influent, effluent and discharged sludge samples. The concentrations of these compounds were particularly high in the discharged sludge samples.

We have investigated the critical behavior near the ferromagnetic transition of TlCo

We have investigated the magnetism and magnetocaloric effect of TlCo2-x Ni x S2 (0 [Formula: see text] x [Formula: see text] 0.05). TlCo2S2 and TlCo1.97Ni0.03S2 are ferromagnetically ordered below 153 K and 142 K with saturated moment 0.82 [Formula: see text] [Formula: see text]/Co and 0.80 [Formula: see text] [Formula: see text]/Co, respectively, while TlCo1.95Ni0.05S2 shows ferromagnetic transition at 132 K. The magnetism displays slightly itinerant character, as inferred from the Rhodes-Wohlfarth ratio. An unusual historical dependence of magnetization in TlCo1.95Ni0.05S2 is consistently observed by scanning both the temperature and magnetic field. The isothermal magnetic entropy change ([Formula: see text] S [Formula: see text]) of TlCo2S2 and TlCo1.95Ni0.05S2 are calculated by Maxwell relation and a temperature averaged entropy change is adopted to estimate the figure of merit for the compounds.

In this paper, we present a new method to synthesize the quasi-one-dimensional (1D) BaCoO 3 single crystal using (NaOH+KOH) flux at ambient pressure. Composition analysis showed that the crystal was stoichiometric. The structure was determined by single crystal x-ray diffraction. This study sheds new light on the synthesis of the low dimensional cobalt oxides. At the end, the physical properties were investigated in BaCoO 3 single crystal. It was found that the titled compound is electrically insulating with a gap of 61 meV along the chain.

Magnetic refrigeration based on the magnetocaloric effect (MCE) is an environment-friendly, high-efficiency technology. It has been believed that a large MCE can be realized in the materials with a first-order magnetic transition (FOMT). Here, we found that TlFe3Te3 is a ferromagnetic metal with a first-order magnetic transition occurring at Curie temperature TC = 220 K. The maximum values of magnetic entropy change (Δ"Equation missing") along the crystallographic c-axis, estimated from the magnetization data, reach to 5.9 J kg−1K−1 and 7.0 J kg−1 K−1 for the magnetic field changes, ΔH = 0–1 T and 0–2 T, respectively, which is significantly larger than that of MCE materials with a second-order magnetic transition (SOMT). Besides the large ΔSM, the low-level both thermal and field hysteresis make TlFe3Te3 compound an attractive candidate for magnetic refrigeration. Our findings should inspire the exploration of high performance new MCE materials.

${\mathrm{Re}}_{6}\mathrm{Hf}$, which crystallizes in $\ensuremath{\alpha}$-Mn structure(space group $I\overline{4}3m)$ without a spatial inversion center, is a superconductor with a superconducting transition temperature ${T}_{c}\phantom{\rule{4pt}{0ex}}\ensuremath{\approx}6.2\phantom{\rule{4pt}{0ex}}\mathrm{K}$. The measurements of magnetic susceptibility $(\ensuremath{\chi})$, resistivity $(\ensuremath{\rho})$, and specific heat capacity $(C)$ were carried out. Bulk superconductivity is revealed by the jump at ${T}_{c}$ of the specific heat with $\mathrm{\ensuremath{\Delta}}C/{\ensuremath{\gamma}}_{n}{T}_{c}\phantom{\rule{4pt}{0ex}}\ensuremath{\approx}\phantom{\rule{4pt}{0ex}}1.63$, suggesting moderate electron-electron coupling strength in this system. The upper critical field ${\ensuremath{\mu}}_{0}{H}_{c2}^{WHH}(0)$ was estimated to be of 89 kOe, and ${\ensuremath{\mu}}_{0}{H}_{c2}^{GL}(0)=107$ kOe, which is close to the Pauli limiting field. The Ginzburg Landau parameter ${\ensuremath{\kappa}}_{GL}=50.2$, indicates that ${\mathrm{Re}}_{6}\mathrm{Hf}$ is a type-II superconductor. The temperature dependence of the electronic specific heat ${C}_{el}(T)$ in the superconducting state can be explained by BCS theory. Furthermore, the magnetic-field dependence of $\ensuremath{\gamma}(H)$ is found to be linear with respect to $H$. These results imply a dominant $s$-wave superconductivity in ${\mathrm{Re}}_{6}\mathrm{Hf}$.

After growing successfully TaP single crystal, we measured its longitudinal resistivity (rhoxx) and Hall resistivity (rhoyx) at magnetic fields up to 9T in the temperature range of 2-300K. It was found that at 2K its magnetoresistivity (MR) reaches to 328000 percent, at 300K to 176 percent at 8T, and both do not appear saturation. We confirmed that TaP is indeed a low carrier concentration, hole-electron compensated semimetal, with a high mobility of hole muh=371000 cm2V-1s-1, and found that a magnetic-field-induced metal-insulator transition occurs at room temperature. Remarkably, as a magnetic field (H) is applied in parallel to the electric field (E), the negative MR due to chiral anomaly is observed, and reaches to -3000 percent at 9T without any signature of saturation, too, which distinguishes with other Weyl semimetals (WSMs). The analysis on the Shubnikov-de Haas (SdH) oscillations superimposing on the MR reveals that a nontrivial Berry phase with strong offset of 0.3958 realizes in TaP, which is the characteristic feature of the charge carriers enclosing a Weyl nodes. These results indicate that TaP is a promising candidate not only for revealing fundamental physics of the WSM state but also for some novel applications.

Well understanding about the physical properties of FeTe compound, as a parent of superconducting Fe(Te, Se) system, is very important for exploring superconducting mechanism in the Fe-based superconductors. Here, based on the transport and magnetization measurements, we report the Cu doping effects on the physical properties of Fe1.05Te compound. We found that in the undoped sample, an antiferromagnetic (AFM) transition accompanying a semiconductor–metal transition occurs at 70 K. With the increase of Cu content x, the AFM transition temperature decreases monotonously at first. When x ⩾ 0.05 , both the metallic behavior and long-range AFM ordering disappear. Meanwhile, a spin-glass state emerges at low temperatures. The evolution of the transport and the magnetic properties with the Cu content x is summarized and a phase diagram is proposed. Our results indicate that a local spin picture may be more appropriate than an itinerant model for the Fe1.05Te compound.

We have investigated the critical behavior of Fe2.85GeTe2 single crystals near the paramagnetic-ferromagnetic transition by bulk dc magnetization measurements. The critical exponents β, γ and δ, obtained from modified Arrott plot, Kouvel-Fisher method, and critical isothermal magnetization analysis, could fulfill the Widom scaling law. The self-consistency and reliability of these exponents are further verified by the magnetic state equations below and above the Curie temperature at high magnetic field. In addition, the exchange distance deduced from the susceptibility exponent is shown to decay as [Formula: see text]. Based on the observations, we suggest that the competition between direct magnetic exchange and Coulombic and/or RKKY interactions should be responsible for the intrinsic magnetism in this system.

We have investigated the critical behavior near the ferromagnetic transition of TlCo2S2 single crystals and the magnetic properties of Tl(Co0.95Ni0.05)2S2 by means of magnetization measurements. The obtained critical exponents β, γ and δ of TlCo2S2 could basically satisfy the scaling equations and are found very close to the prediction of the tricritical mean-field theory. 5[Formula: see text] Ni doping drives the system to an antiferromagnetic ground state which is unstable to magnetic field, yielding metamagnetic transition. The possible existence of a tricritical point (TCP) in Tl(Co0.95Ni0.05)2S2 is also discussed.

Combining photoemission spectroscopy, Raman spectroscopy, and first-principles calculations, we characterize superconducting TlNi2Se2 as a material with weak electronic Coulomb correlations leading to a bandwidth renormalization of 1.4. We identify a camelback-shaped band, whose energetic position strongly depends on the selenium height. While this feature is universal in transition metal pnictides, in TlNi2Se2 it lies in the immediate vicinity of the Fermi level, giving rise to a pronounced van Hove singularity. The resulting heavy band mass resolves the apparent puzzle of a large normal-state Sommerfeld coefficient [H. Wang et al., Phys. Rev. Lett 111, 207001 (2013)] in this weakly correlated compound.

The physical properties of CsNi$_{2}$Se$_{2}$ were characterized by electrical resistivity, magnetization and specific heat measurements. We found that the stoichiometric CsNi$_{2}$Se$_{2}$ compound is a superconductor with a transition temperature \textit{T$_{c}$}=2.7K. A large Sommerfeld coefficient $\gamma$$_{n}$ ($\sim$77.90 mJ/mol$\cdot$K$^{-2}$), was obtained from the normal state electronic specific heat. However, the Kadowaki-Woods ratio of CsNi$_{2}$Se$_{2}$ was estimated to be about 0.041$\times$10$^{-5}$ $\mu\Omega$$\cdot$cm(mol$\cdot$K/mJ)$^{2}$, indicating the absence of strong electron-electron correlations in this compound. In the superconducting state, we found that the zero-field electronic specific heat data, $C_{es}(T)$ (0.5K $\leq$ T $, Comment: 5 pagers, 4 figures

We report the pressure dependence of the superconducting transition temperature ${T}_{c}$ in ${\mathrm{TlNi}}_{2}{\mathrm{Se}}_{2\ensuremath{-}x}{\mathrm{S}}_{x}$ detected via the ac susceptibility method. The pressure-temperature phase diagram constructed for ${\mathrm{TlNi}}_{2}{\mathrm{Se}}_{2}$, ${\mathrm{TlNi}}_{2}{\mathrm{S}}_{2}$, and ${\mathrm{TlNi}}_{2}\mathrm{SeS}$ exhibits two unexpected features: (a) a sudden collapse of the superconducting state at moderate pressure for all three compositions and (b) a dome-shaped pressure dependence of ${T}_{c}$ for ${\mathrm{TlNi}}_{2}\mathrm{SeS}$. These results point to the nontrivial role of S substitution and its subtle interplay with applied pressure, as well as interesting superconducting properties of the ${\mathrm{TlNi}}_{2}{\mathrm{Se}}_{2\ensuremath{-}x}{\mathrm{S}}_{x}$ system.

Low-temperature thermal conductivity measurements were performed on single crystals of $\mathrm{TlNi}{}_{2}\mathrm{Se}{}_{2}$, a nickel chalcogenide heavy-electron superconductor with ${T}_{c}\ensuremath{\simeq}3.7$ K. In zero field, the residual electronic contribution at $T\ensuremath{\rightarrow}0$ K (${\ensuremath{\kappa}}_{0}/T$) was well separated from the total thermal conductivity, which is less than 0.45% of its normal-state value. Such a tiny residual ${\ensuremath{\kappa}}_{0}/T$ is unlikely contributed by the nodal quasiparticles. The nodeless gap structure is supported by the very weak field dependence of ${\ensuremath{\kappa}}_{0}(H)/T$ in low magnetic fields. In the whole field range, ${\ensuremath{\kappa}}_{0}(H)/T$ exhibits an $\mathsf{S}$-shaped curve, as in the case of nickel pnictides $\mathrm{BaNi}{}_{2}\mathrm{As}{}_{2}$ and $\mathrm{SrNi}{}_{2}\mathrm{P}{}_{2}$. This common feature of nickel-based superconductors can be explained by multiple nodeless superconducting gaps.

We have made the first observation of superconductivity in ${\mathrm{TlNi}}_{2}{\mathrm{Se}}_{2}$ at ${T}_{C}=3.7\text{ }\text{ }\mathrm{K}$, and it appears to involve heavy electrons with an effective mass ${m}^{*}=(14--20){m}_{b}$, as inferred from the normal-state electronic specific heat and the upper critical field, ${H}_{C2}(T)$. We found that the zero-field electronic specific-heat data, ${C}_{\mathrm{es}}(T)$ ($0.5\text{ }\text{ }\mathrm{K}\ensuremath{\le}Tl3.7\text{ }\text{ }\mathrm{K}$) in the superconducting state can be fitted with a two-gap BCS model, indicating that ${\mathrm{TlNi}}_{2}{\mathrm{Se}}_{2}$ seems to be a multiband superconductor, which is consistent with the band calculation for the isostructural ${\mathrm{KNi}}_{2}{\mathrm{S}}_{2}$. It is also found that the electronic specific-heat coefficient in the mixed state ${\ensuremath{\gamma}}_{N}(H)$ exhibits a ${H}^{1/2}$ behavior, which is considered as a common feature of the $d$-wave superconductors. ${\mathrm{TlNi}}_{2}{\mathrm{Se}}_{2}$, as a $d$-electron system with heavy electron superconductivity, may be a bridge between cuprate- or iron-based and conventional heavy-fermion superconductors.

The magnetic properties of ThCr${}_{2}$Si${}_{2}$-type single crystals $A$Co${}_{2}$Se${}_{2}$ ($A=\text{K}$, Rb, and Cs) were investigated by means of magnetic susceptibilities and isothermal magnetizations measurements. The ferromagnetic phase transition temperatures are $\ensuremath{\approx}$74 and 76 K for $A=\text{K}$ and Rb, respectively. A possible antiferromagnetic phase transition occurs around 80 K in susceptibility and a metamagnetismlike behavior is first discovered at a field of $\ensuremath{\approx}$3.5 T for $H\ensuremath{\parallel}ab$ plane in CsCo${}_{2}$Se${}_{2}$ below 62 K. The susceptibilities in the paramagnetic state obey the modified Curie-Weiss law quite well in all samples. Moreover, the derived effective magnetic moments of the Co atom are about 2.21, 2.04, and 2.04 ${\ensuremath{\mu}}_{B}$/Co for $A=\text{K}$, Rb, and Cs, respectively. The generalized Rhodes-Wohlfarth ratio indicates an itinerant magnetism in this series. Finally, we discussed the magnetic properties in this series within the frameworks of the self-consistent renormalization and Takahashi's theory of spin fluctuations.

We have made the first observation of superconductivity in TlNi2Se2 at T(C)=3.7 K, and it appears to involve heavy electrons with an effective mass m*=(14-20)m(b), as inferred from the normal-state electronic specific heat and the upper critical field, H(C2)(T). We found that the zero-field electronic specific-heat data, C(es)(T) (0.5 K≤T3.7 K) in the superconducting state can be fitted with a two-gap BCS model, indicating that TlNi2Se2 seems to be a multiband superconductor, which is consistent with the band calculation for the isostructural KNi2S2. It is also found that the electronic specific-heat coefficient in the mixed state γN(H) exhibits a H(1/2) behavior, which is considered as a common feature of the d-wave superconductors. TlNi2Se2, as a d-electron system with heavy electron superconductivity, may be a bridge between cuprate- or iron-based and conventional heavy-fermion superconductors.

The measurements on magnetization (M), resistivity (ρ) and specific heat (C) were carried out for the ferromagnetic CeTi Ni x Ge3 (0.0 x 0.45) system. It was found that the Curie temperature, T C, decreases with increasing Ni content, x, and reaches zero kelvin near a critical content x cr = 0.44. A new phase diagram is constructed based on these measurements. The non-Fermi liquid (nFL) behavior in ρ(T), and (T 0/T) relationship in C/T in the samples near x cr, demonstrate that strong spin fluctuation emerges in these samples, indicating that they are near a quantum critical point (QCP). Our results indicate that CeTi Ni x Ge3 may provide another platform to study exotic quantum phenomena near ferromagnetic QCP.

After our first discovery of multi-band superconductivity (SC) in the TlNi2Se2 crystal, we successfully grew a series of TlNi2Se(2-x)S(x) (0.0 ≤ x ≤ 2.0) single crystals. Measurements of resistivity, specific heat, and susceptibility were carried out on these crystals. Superconductivity with T(C) = 2.3 K was first observed in the TlNi2S2 crystal, which also appears to involve heavy electrons with an effective mass m* = 13-25 m(b), as inferred from the normal state electronic specific heat and the upper critical field, H(C2)(T). It was found that bulk SC and heavy-electron behavior is preserved in all the studied TlNi2Se(2-x)S(x) samples. In the mixed state, a novel change of the field dependence of the residual specific heat coefficient, γ(N)(H), occurs in TlNi2Se(2-x)S(x) with increasing S content. We also found that the T(C) value changes with the disorder degree induced by the partial substitution of S for Se, characterized by the residual resistivity ratio (RRR). Thus, the TlNi2Se(2-x)S(x) system provides a platform to study the effect of disorder on the multi-band SC.

The excess Fe atoms which unavoidably exist in the Fe(Te, Se, S) crystal lattice result in a complicated antiferromagnetic ground state as well as the suppression of superconductivity. As a result, there are still discrepancies on their phase diagrams. In this paper, we report the synthesis of Fe1+δTe1-xSx (0 ≤ x ≤ 0.12) single crystals by a melting method. Superconductivity was greatly improved after air annealing by which we partially removed the excess Fe atoms. Based on the resistivity and susceptibility measurements, we concluded a phase diagram of the Fe1+δTe1-xSx (0 ≤ x ≤ 0.12) system with fewer excess iron atoms. We found a coexisting region (0.07 ≤ x ≤ 0.11) of antiferromagnetic order and bulk superconductivity. This phase diagram is similar to that of the K- or Co-doped BaFe2As2 system, as well as the Fe(Te, Se) system, implying a commonality of the iron-based superconductors.