Understanding magnetocrystalline anisotropy based on orbital and quadrupole moments.

Understanding magnetocrystalline anisotropy (MCA) is fundamentally important for developing novel magnetic materials. Therefore, clarifying the relationship between MCA and local physical quantities observed by spectroscopic measurements, such as the orbital and quadrupole moments, is necessary. In this review, we discuss MCA and the distortion effects in magnetic materials with transition metals (TMs) based on the orbital and quadrupole moments, which are related to the spin-conserving and spin-flip terms in the second-order perturbation calculations, respectively. We revealed that orbital moment stabilized the spin moment in the direction of the larger orbital moment, while the quadrupole moment stabilized the spin moment along the longitudinal direction of the spin-density distribution. The MCA of the magnetic materials with TMs and their interfaces can be determined from the competition between these two contributions. We showed that the perpendicular MCA of the face-centered cubic Ni with tensile tetragonal distortion arose from the orbital moment anisotropy, whereas that of Mn-Ga alloys originated from the quadrupole moment of spin density. In contrast, in the Co/Pd(111) multilayer and Fe/MgO(001), both the orbital moment anisotropy and quadrupole moment of spin density at the interfaces contributed to the perpendicular MCA. Understanding the MCA of magnetic materials and interfaces based on orbital and quadrupole moments is essential to design MCA of novel magnetic applications.

Seebeck-driven transverse thermoelectric generation.

When a temperature gradient is applied to a closed circuit comprising two different conductors, a charge current is generated via the Seebeck effect1. Here, we utilize the Seebeck-effect-induced charge current to drive 'transverse' thermoelectric generation, which has great potential for energy harvesting and heat sensing applications owing to the orthogonal geometry of the heat-to-charge-current conversion2-9. We found that, in a closed circuit comprising thermoelectric and magnetic materials, artificial hybridization of the Seebeck effect into the anomalous Hall effect10 enables transverse thermoelectric generation with a similar symmetry to the anomalous Nernst effect11-27. Surprisingly, the Seebeck-effect-driven transverse thermopower can be several orders of magnitude larger than the anomalous-Nernst-effect-driven thermopower, which is clearly demonstrated by our experiments using Co2MnGa/Si hybrid materials. The unconventional approach could be a breakthrough in developing applications of transverse thermoelectric generation.

Detecting quadrupole: a hidden source of magnetic anisotropy for Manganese alloys.

Mn-based alloys exhibit unique properties in the spintronics materials possessing perpendicular magnetic anisotropy (PMA) beyond the Fe and Co-based alloys. It is desired to figure out the quantum physics of PMA inherent to Mn-based alloys, which have never been reported. Here, the origin of PMA in ferrimagnetic Mn3- δ Ga ordered alloys is investigated to resolve antiparallel-coupled Mn sites using x-ray magnetic circular and linear dichroism (XMCD/XMLD) and a first-principles calculation. We found that the contribution of orbital magnetic moments in PMA is small from XMCD and that the finite quadrupole-like orbital distortion through spin-flipped electron hopping is dominant from XMLD and theoretical calculations. These findings suggest that the spin-flipped orbital quadrupole formations originate from the PMA in Mn3- δ Ga and bring the paradigm shift in the researches of PMA materials using x-ray magnetic spectroscopies.

Electronic structure of AlFeN films exhibiting crystallographic orientation change from c- to a-axis with Fe concentrations and annealing effect.

Wurtzite AlN film is a promising material for deep ultraviolet light-emitting diodes. However, some properties that attribute to its crystal orientation, i.e., c-axis orientation, are obstacles in realizing high efficiency devices. Constructing devices with non-c-axis oriented films is a solution to this problem; however, achieving it with conventional growth techniques is difficult. Recently, we succeeded in growing a-axis oriented wurtzite heavily Fe-doped AlN (AlFeN) films via sputtering. In this article, we report the electronic structures of AlFeN films investigated using soft X-ray spectroscopies. As-grown films were found to have conduction and valence band structures for a film with c-axis in film planes. Simultaneously, it was found that large gap states were formed via N-p and Fe-d hybridization. To remove the gap states, the films were annealed, thereby resulting in a drastic decrease of the gap states while maintaining a-axis orientation. We offer heavy Fe-doping and post annealing as a new technique to obtain non-polar AlN films.

Erratum: Realizing Room-Temperature Resonant Tunnel Magnetoresistance in Cr/Fe/MgAl2O4 Quasi-Quantum Well Structures.

[This corrects the article DOI: 10.1002/advs.201901438.].

Realizing Room-Temperature Resonant Tunnel Magnetoresistance in Cr/Fe/MgAl2O4 Quasi-Quantum Well Structures.

The quantum well (QW) realizes new functionalities due to the discrete electronic energy levels formed in the well-shaped potential. Magnetic tunnel junctions (MTJs) combined with a quasi-QW structure of Cr/ultrathin-Fe/MgAl2O4(001)/Fe, in which the Cr quasi-barrier layer confines Δ 1 up-spin electrons to the Fe well, are prepared with perfectly lattice-matched interfaces and atomic layer number control. Resonant peaks are clearly observed in the differential conductance of the MTJs due to the formation of QWs. Furthermore, enhanced tunnel magnetoresistance (TMR) peaks at the resonant bias voltages are realized for the MTJs at room temperature, i.e., it is observed that TMR ratios at specific and even high bias-voltages (V bias) are larger than zero-bias TMR ratios for the MTJs with odd Fe atomic layers, in contrast to the earlier experimental studies. In addition, a new finding in this study is unique sign changes in the temperature coefficient of resistance (TCR) depending on the Fe thickness and V bias, which is interpreted as a signature of the QW formation of Δ1 symmetry electronic states. The present study suggests that the spin-dependent resonant tunneling via the QWs formed in Cr/ultrathin-Fe/MgAl2O4/Fe structures should open a new pathway to achieve a large TMR at practically high V bias.

Exploring half-metallic Co-based full Heusler alloys using a DFT+U method combined with linear response approach.

A density functional theory (DFT)+U method based on linear response (LR) theory was applied to investigate the electronic structures of a Co-based ternary full Heusler alloy Co2YSi to explore half-metallic (HM) ferromagnets with a wide HM gap. The LR-based DFT+U calculations tend to obtain a reasonable correlation parameter for the Y site, while the correlation of the Co site misdirects to the unphysical ground state due to the overestimated parameter value that arises from the delocalized electronic structure of Co. Furthermore, we found that the HM gap of Co2MnSi originates from the Co orbital in the conduction state and the Co-Mn hybridizing t2g orbital in the valence state around the Fermi energy. This means that the HM gap is a tunable property by selecting the Y element and/or mixing several elements into the Y site through t2g atomic-orbital coupling. Our LR-based DFT+U method was extended to other ternary Co2YSi and quaternary Co2(Y,Mn)Si. We found that Co2(Ti0.25,Mn0.75)Si and Co2(Fe0.25,Mn0.75)Si show HM nature, with the Fermi energy being at almost the center of the minority band gap, which leads to high thermal stability.

Novel recombinant feline interferon carrying N-glycans with reduced allergy risk produced by a transgenic silkworm system.

BACKGROUND: The generation of recombinant proteins for commercialisation must be cost-effective. Despite the cost-effective production of recombinant feline interferon (rFeIFN) by a baculovirus expression system, this rFeIFN carries insect-type N-glycans, with core α 1,3 fucosyl residues that act as potential allergens. An alternative method of production may yield recombinant glycoproteins with reduced antigenicity. RESULTS: A cDNA clone encoding the fifteenth subtype of FeIFN-α (FeIFN-α15) was isolated from a Japanese domestic cat. This clone encoded a protein of 189 amino acids with a molecular mass of 21.1 kDa. The rFeIFN-α15 was expressed using a transgenic silkworm system, which was expected to yield an N-glycan structure with reduced antigenicity compared with the protein produced by the baculovirus system. The resulting rFeIFN-α15 accumulated in the sericin layer of silk fibres and was easily extracted and purified by column chromatography. The N-terminal amino acid sequence of purified rFeIFN-α15 was identical to the mature form of natural sequence. Moreover, its N-glycans did not include detectable core α 1,3 fucosyl residues. Its anti-vesicular stomatitis virus activity (2.6 × 108 units/mg protein) was comparable to that of the baculovirus-expressed rFeIFN. CONCLUSIONS: The lower allergy risk of rFeIFN produced by the transgenic silkworm system than by the baculovirus expression system is due to the former lacking core α 1,3 fucosyl residues in its N-glycans. The rFeIFN-α15 produced by the transgenic silkworm system may be a prospective candidate for the next generation of rFeIFN in veterinary medicine.

Anatomy of interfacial spin-orbit coupling in Co/Pd multilayers using X-ray magnetic circular dichroism and first-principles calculations.

Element-specific orbital magnetic moments and their anisotropies in perpendicularly magnetised Co/Pd multilayers are investigated using Co L-edge and Pd M-edge angle-dependent x-ray magnetic circular dichroism. We show that the orbital magnetic moments in Co are anisotropic, whereas those in Pd are isotropic. The first-principles density-functional-theory calculations also suggest that the Co/Pd interfacial orbital magnetic moments in Co are anisotropic and contribute to the perpendicular magnetic anisotropy (PMA), and that the isotropic ones in Pd manipulates the Co orbitals at the interface through proximity effects. Orbital-resolved anatomy of Co/Pd interfaces reveals that the orbital moment anisotropy in Co and spin-flipped transition related to the magnetic dipoles in Pd are essential for the appearance of PMA.

Prophylactic clip closure may reduce the risk of delayed bleeding after colorectal endoscopic submucosal dissection.

BACKGROUND AND STUDY AIMS: Endoscopic submucosal dissection (ESD) has a high en bloc resection rate and is widely performed for large superficial colorectal tumors, but delayed bleeding remains one of the most common complications of colorectal ESD. The aim of the present study was to evaluate the clinical efficacy of prophylactic clip closure of mucosal defects for the prevention of delayed bleeding after colorectal ESD. PATIENTS AND METHODS: We enrolled consecutive patients with colorectal lesions between January 2012 and May 2017 in this retrospective study. In the early part of this period, post-ESD mucosal defects were not closed (non-closure group); however, from January 2014, post-ESD mucosal defects were prophylactically closed with clips when possible (closure group). The main outcome measured was delayed bleeding. Variables were analyzed using the chi-squared test, Fisher's exact test, or Student's t-test. RESULTS: Of 156 lesions analyzed, 61 were in the non-closure group and 95 in the closure group. Overall, delayed bleeding occurred in 5 cases (3.2 %). The delayed bleeding rate was 0 % (0/95) in the closure group and 8.2 % (5/61) in the non-closure group ( P  = 0.008). The mean procedure time for closure was 10.4 ±â€Š4.6 min (range 3 - 26 min). CONCLUSIONS: We demonstrated that prophylactic clip closure of mucosal defects might reduce the risk of delayed bleeding after colorectal ESD.

Carney complex: a case with thyroid follicular adenoma without a PRKAR1A mutation.

BACKGROUND: Carney complex (CNC) is a very rare disease. Although thyroid lesions are included in the diagnostic criteria for CNC, they are an infrequent occurrence. CASE PRESENTATION: The patient was a 69-year-old woman who had undergone the removal of a left atrial myxoma 10 years earlier, at the age of 59. At the time of the operation, thyroid ultrasonography (US) revealed multiple hypoechoic nodules. Thyroid scintigraphy revealed an increased uptake of 99mTc in these lesions, which was consistent with toxic multinodular goiter, and she was diagnosed with CNC. Genetic studies showed no mutation in the PRKAR1A (protein kinase A regulatory subunit 1-α) gene. From then on, she received annual brain magnetic resonance imaging (MRI), abdominal computed tomography (CT), and thyroid US examinations. Her follicular thyroid nodules gradually increased in number and size. Although aspiration cytology samples from the thyroid nodules diagnosed them as class III, thyroid cancer could not be ruled out. The patient underwent a partial thyroidectomy, and the pathological diagnosis was multiple follicular adenomas. CONCLUSION: Careful and frequent evaluation of the thyroid gland should be required for CNC patients due to the potential for carcinoma to develop in the context of a variety of follicular thyroid lesions.

Drastic change in density of states upon martensitic phase transition for metamagnetic shape memory alloy Ni2Mn(1+x)In(1-x).

We have unravelled the electronic structure of a class of metamagnetic shape memory alloy Ni2Mn1+x In1-x by combining bulk-sensitive hard x-ray photoelectron spectroscopy and first-principles density-functional calculations. A sharp drop in the Ni 3d e(g) density of states forming a pseudogap in the martensitic phase transition (MPT) for x = 0.36 has been observed near the Fermi level. As a feature of MPT, hysteretic behaviour of this drop has been confirmed in both cooling and warming. This pseudogap is responsible for the giant negative magnetoresistance. The experimental result is well reproduced by the first principle calculation. We have also clarified theoretically that the MPT is linked to a competition of ferromagnetic and anti-ferromagnetic coupling between ordinary and anti-site Mn atoms.

The origin of perpendicular magneto-crystalline anisotropy in L1(0)-FeNi under tetragonal distortion.

We investigated the origin of perpendicular magneto-crystalline anisotropy (MCA) in L1(0)-ordered FeNi alloy using first-principles density-functional calculations. We found that the perpendicular MCA of L1(0)-FeNi arises predominantly from the constituent Fe atoms, which is consistent with recent measurements of the anisotropy of the Fe orbital magnetic moment of L1(0)-FeNi by means of x-ray magnetic circular dichroism. Analysis of the second-order perturbation of the spin-orbit interaction indicates that spin-flip excitations between the occupied majority-spin and unoccupied minority-spin bands make a considerable contribution to the perpendicular MCA, as does the spin-conservation term for the minority-spin bands. Furthermore, the MCA energy increases as the in-plane lattice parameter decreases (increasing the axial ratio c/a). The increase in the MCA energy can be attributed to further enhancement of the spin-flip term due to modulation of the Fe d(xy) and d(x(2) - y(2)) orbital components around the Fermi level under compressive in-plane distortion.

Superconductivity of Ni-Nb-Zr-H glassy alloys with nanoclusters.

We investigated the hydrogen effect on superconductivity in the (Ni0.36Nb0.24Zr0.40)(100-x)H(x)(0 < or = x < or = 6.4) glassy alloys with nanoclusters, as a function of temperature. The resistivity of these alloys started to drop from onset temperature of around 9.5 K. The (Ni0.36Nb0.24Zr0.40)98.6H1.6 showed zero resistance at 2.1 K. However, the application of a magnetic field > 4.6 T arrested the drop of resistivity, showing the existence of superconductivity of type II. The maximum onset temperature of 11.3 K was observed at 4.4 at% H. The superconducting behavior of the glassy alloys would be associated with electron pair transport along zigzag paths, which link the shortened atomic -Ni-Ni-Ni- array in the Zr5Ni5Nb3 clusters, and tunneling among the clusters.

The effect of the interface oxidation on tunneling conductance of Co(2)MnSi/MgO/Co(2)MnSi magnetic tunnel junction.

We investigate and discuss the effects of interfacial oxidation on electronic structures and tunnel conductance of the Co(2)MnSi/MgO/Co(2)MnSi(001) magnetic tunnel junction (MTJ) on the basis of first-principles calculations. It is found that the MnSi termination tends to be oxidized compared with the Co termination because of the relaxation of atomic positions in the MnSi-terminated interface. Furthermore, we found that the single oxide layer inserted on both sides of the junction greatly decreases the tunnel conductance of the MTJ in parallel magnetization. We concluded that the relaxation of the Mn atomic position in the oxidized junction reduces the coupling of the Δ(1) states between the Co(2)MnSi electrode and the MgO barrier and causes significant interfacial scattering of the majority-spin electrons with Δ(1) symmetry at the oxidized layer.

Half-metallic interface between a Heusler alloy and Si.

The interface between the half-Heusler alloy CoFeSi and Si is investigated by using first-principles density-functional calculations. Although CoFeSi has not been fabricated yet, its formation energy turns out to be negative. Within the generalized gradient approximation, CoFeSi shows nearly half-metallic properties, and its lattice constant is about 5.38 Å; this value is relatively close to the lattice constant of Si. We here chiefly investigate the CoFeSi/Si (110) interface, and find that the half-metallic properties are almost preserved at a specific (110) interface. Furthermore, the interfacial structure which leads to the high spin polarization has the lowest energy of the (110) interfacial patterns examined in this work. The half-metallicity at the interfaces is similarly observed in the densities of states projected onto delocalized sp states, and this suggests the relevance of the high spin polarization to transport properties.

Coherent tunnelling conductance in magnetic tunnel junctions of half-metallic full Heusler alloys with MgO barriers.

We have carried out electronic structure and transport calculations for magnetic tunnel junctions (MTJ) composed of MgO and a half-metallic full Heusler alloy Co(2)MnSi on the basis of the density functional theory and the Landauer formula. We find that the density of states of Co atoms at the Co(2)MnSi/MgO(001) interface shifts toward the higher energy side due to the reduced symmetry, leading to a reduction of the spin polarization at the interface. Furthermore, we show that the majority-spin transmittance as a function of the in-plane wavevector [Formula: see text] has a broad peak centred at [Formula: see text] due to the tunnelling from the Δ(1) channel of Co(2)MnSi, while the transmittance from the Δ(5) channel is three orders of magnitude smaller than that of the Δ(1) channel. These results indicate that coherent tunnelling through the Δ(1) band is dominant also in an MTJ with Co(2)MnSi and an MgO barrier, like in Fe/MgO/Fe(001) MTJ and related systems.

The computational materials design of (Ga, Cr)N: effects of co-doping on exchange interactions.

We investigate the effect of O or Be co-doping on the exchange interaction between Cr spins in (Ga, Cr)N by means of first-principles calculations based on the density-functional theory. The ferromagnetic exchange interactions are reduced by doping Be around Cr. On the other hand, O doping reduces the ferromagnetic interaction remarkably only for the case of Cr-O-Cr complex formation. The enhancement of the ferromagnetic exchange interaction cannot be achieved by doping O or Be impurities. However, the O and Be impurities can help the clustering of Cr atoms due to the enhancement of the attractive interaction between Cr atoms.

Expression and localization of MUC1, MUC2, MUC5AC and small intestinal mucin antigen in pancreatic tumors.

Alterations in the expression of mucin family members play an important role as well as alterations in oncogenes and onco-suppressor genes in carcinogenesis and progression of pancreatic cancer. We analyzed the expression and localization of MUC1, MUC2, MUC5AC and small intestinal mucin antigen (SIMA) in pancreatic tumors. MUC1 expression was observed in almost all samples, whereas MUC2 expression was not. MUC5AC expression was observed in 73.9% of the cancerous regions, 48.7% of the dysplastic regions and 72.0% of the hyperplastic regions but not in the normal pancreatic duct. SIMA expression was observed in 45.7% of cancerous regions, 17.9% of the dysplastic regions and 8.0% of the hyperplastic regions. Furthermore, stromal expression of MUC1, MUC5AC and SIMA was observed in 37.0%, 60.9% and 26.1% of the cancerous regions, respectively. Stromal expression of these mucins was not observed in the hyperplastic regions and normal pancreatic duct and was observed in only two dysplastic regions. The survival of pancreatic cancer patients with stromal expression of MUC1 or SIMA was worse than that of other patients (P=0.04). In conclusion, the localization of mucin expression, especially stromal expression of MUC1 or SIMA, might be a prognostic factor for patients with pancreatic cancer.

Screening and Field Trials of Virus Resistant Sources in Capsicum spp.

Thirty-seven Capsicum accessions containing cultivated and wild species were screened for resistance to Cucumber mosaic virus (CMV), and were also investigated for their response to Tomato aspermy virus (TAV), Tomato mosaic virus (ToMV), Pepper mild mottle virus (PMMoV), and Tomato spotted wilt virus (TSWV). C. baccatum PI 439381-1-3 (PI 439381-1-3), C. frutescens LS 1839-2-4 (LS 1839-2-4), and C. frutescens cv. Tabasco (cv. Tabasco) showed a hypersensitive reaction against CMV-Y, and thus were not systemically infected. Only inoculated leaves of C. annuum cv. Sapporo-oonaga and cv. Nanbu-oonaga were infected with CMV-Y, and viral infection did not spread systemically. These five accessions (PI 439381-1-3, LS 1839-2-4, cv. Tabasco, cv. Sapporo-oonaga, and cv. Nanbu-oonaga) were considered resistant to CMV-Y. These accessions were also resistant to other CMV isolates, but not to the TAV isolate. PI 439381-1-3, LS1839-2-4, cv. Sapporo-oonaga, and cv. Nanbu-oonaga were susceptible to PMMoV, while PI 439381-1-3 and LS1839-2-4 showed systemic necrosis. All CMV-resistant accessions were susceptible to TSWV. Field tests of eight Capsicum accessions, including CMV, PMMoV, and/or TSWV-resistant accessions, demonstrated that most of the PI 439381-1-3 plants were not infected with CMV and PMMoV among the virus-infested fields. As occurred with mechanical inoculation, LS 1839-2-4, cv. Tabasco, cv. Sapporo-oonaga, and cv. Nanbu-oonaga were hard to infect with CMV in the field.