Spin reorientation is a magnetic phase transition in which rotation of the magnetization vector with respect to the crystallographic axes occurs upon a change in the temperature or magnetic field. For example, SmFeO 3 shows a magnetization rotation from the c axis above 480 K to the a axis below 450 K, known as the Γ 4 → Γ 2 transition. This work reports the successful synthesis of the new single-crystal perovskite SmFe 0.75 Mn 0.25 O 3 and finds interesting spin reorientations above and below room temperature. In addition to the spin reorientation of the Γ 4 → Γ 2 magnetic phase transition observed at around T SR2 = 382 K, a new spin reorientation, Γ 2 → Γ 1 , was seen at around T SR1 = 212 K due to Mn doping, which could not be observed in the parent rare earth perovskite compound. This unexpected spin configuration has complete antiferromagnetic order without any canting-induced weak ferromagnetic moment, resulting in zero magnetization in the low-temperature regime. M – T and M – H measurements have been made to study the temperature and magnetic-field dependence of the observed spin reorientation transitions.
We have successfully synthesized a single-crystal sample of the layered structure ferromagnet Fe3GeTe2 and present the results of its complete characterization using powder X-ray diffraction (XRD), magnetic susceptibility χ(T), isotherm magnetization \(M(H)\), specific heat \(C(T)\), and electrical resistivity ρ(T) measurements. The rietveld refinement of the powder XRD data confirms that Fe3GeTe2 crystallizes in the space group \(p6_{3}/mmc\). The χ(T), \(C(T)\), and ρ(T) data indicate bulk ferromagnetic ordering at \(T_{\text{C}} = 220\) K with a saturation moment of 1.625 µB/Fe at zero temperature. The magnetic measurements of the external magnetic field \(H\) applied along the \(c\)-axis and \(ab\)-plane show a large anisotropy in this material. We found that the modified Arrott plot (\(M^{4}\)–\(H/M\)) rather than the \(M^{2}\)–\(H/M\) plot is obeyed in this material. The generalized Rhodes–Wohlfarth ratio indicates an itinerant magnetism in this material. The spin fluctuation parameters are estimated and the magnetic properties are discussed in the framework of the self-consistent renormalization (SCR) and Takahashi theory of spin fluctuations.
To evaluate the image resolutions in global teleophthalmology using 2 smartphones.A standard resolution test card and two human eyes (one eye wearing a contact lens) were imaged with an iPhone 4S adapted for slitlamp biomicroscopy in Hangzhou, Zhejiang, China. An iPhone 5 was used as a receptor on the other side of the world (Miami, FL). The real-time images and still images were transferred through Skype from Hangzhou to Miami during slitlamp eye examination. The real-time resolutions captured and displayed on the both phones at different places were measured. There was vocal communication concurrent between two parties during image transference and the examination by the slitlamp biomicroscopy performed in Hangzhou.The real-time and still images were transferred between two cities while two operators talked with each other smoothly and without difficulty. The viewer in Miami was able to instruct the operator in Hangzhou to thoroughly examine the eye using the slitlamp microscopy with different magnification settings and illumination settings. The resolution of the still images recorded in the iPhone in Hangzhou was higher than that of the real-time images on the screen. The main features of the eye were recognizable in real-time.The study demonstrated that global teleophthalmology is feasible using two smartphones. The system is simple, portable, and affordable, and the image quality in still and real-time images is acceptable for real-time teleophthalmology.
Silver nanoparticles (AgNPs) are increasingly utilized in a number of applications. This study was designed to investigate AgNPs induced cytotoxicity, oxidative stress and apoptosis in rat tracheal epithelial cells (RTE). The RTE cells were treated with 0, 100 μg/L and 10,000 μg/L of the AgNPs with diameters of 10 nm and 100 nm for 12 hr. The cell inhibition level, apoptosis ratio, reactive oxygen species (ROS), malondialdehyde (MDA) and metallothionein (MT) content were determined. The mRNA expression of cytoc, caspase 3, and caspase 9 was measured by quantitative real-time polymerase chain reaction (qRT-PCR). In addition, we also analyzed the cytoc, caspase 3, pro-caspase 3, caspase 9, and pro-caspase 9 protein expression by western blotting. Electric cell-substrate impedance sensing (ECIS) analysis showed that the growth and proliferation of RTE cells were significantly inhibited in a dose-dependent manner under AgNPs exposure. The cell dynamic changes induced by 10 nm AgNPs were more severe than that of the 100 nm AgNPs exposure group. The intracellular MT, ROS, and MDA content increased when the exposure concentration increased and size reduced, whereas Ca2+-ATPase activity and Na+/K+-ATPase activity changed inversely. The relative expression of protein of cytoc, caspase 3, and caspase 9 were upregulated significantly, which indicated that AgNPs induced apoptosis of RTE cells through the caspase-dependent mitochondrial pathway. Our results demonstrate that AgNPs caused obvious cytotoxicity, oxidative stress, and apoptosis in RTE cells, which promoted the releasing of cytochrome C and pro-apoptotic proteins into the cytoplasm to activate the caspase cascade and finally led to apoptosis.
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≤T<3.7 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.
Abstract Topological metals, including Dirac and Weyl semimetals, represent a wide class of quantum materials with non-trivial electronic band structures. The essential properties of Dirac or Weyl fermions, including light effective mass and high mobility, have been observed in a number of semimetal compounds, which in turn exhibit large positive magnetoresistances. Here, we report an unexpected observation of all these properties in α -gallium (α-Ga) single crystals, a pure metal that is in the liquid phase at room temperature and ambient pressure. Based on systematical transport measurements, α -Ga single crystal is found to exhibit large magnetoresistance, reaching about 1.66 × 10 6 per cent at 2 K in a magnetic field of 9 T. At low temperatures the de Haas–van Alphen and Shubinikov de Hass quantum oscillations show ultrahigh mobility and very small cyclotron effective mass for charge carriers, together with a non-trivial Berry phase. Combined with first-principle band structure calculations, these properties demonstrate α -Ga as a rare topological pure metal. Furthermore, superconductivity with T c of ~0.9 K is confirmed by both specific heat and resistivity measurements. These findings suggest that α -Ga is a unique pure metal displaying both non-trivial topological and superconducting properties.
We report the successful synthesis and characterization of a new layered diluted magnetic semiconductor (DMS) La(Zn,Mn,Cu)AsO which is isostructural to Fe-based "1111" superconductor. Mn and Cu are codoped into the same Zn sites to provide local moments and carriers, respectively. A ferromagnetic transition with the highest TC of ∼ 8 K has been observed for from magnetization measurements. Iso-thermal magnetization plots show that the compound has a coercive field, ∼ 500 Oe, much smaller than that in (La,Ba)(Zn,Mn)AsO. The resistivity of all samples display semiconducting behavior with the doping level up to 15%.
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