Search

The demonstration of the spin-charge conversion, especially with enhanced spin Hall conductivity, is crucial for the development of energy-efficient spintronic devices such as spin-orbital torque (SOT) based magnetoresistive random access memories. In this work, fully epitaxial Ru/Cu heterostructures were fabricated with interface engineering and nanolayer insertions consisting of Cu (1nm)/Ru (1nm) structures with different numbers of periods. The atomically controlled interface was confirmed by the high-resolution high-angle annular dark-field scanning transmission electron microscopy, and the epitaxial relationship persists even in the hybrid nanolayer insertion structures. The spin current generation was detected by the measurement of unidirectional spin Hall magnetoresistance, and the effective damping-like spin Hall efficiency (ξ_DL) was further quantitatively evaluated by the spin-torque ferromagnetic resonance with thickness dependence of the ferromagnetic layer. It is found that the sharp interface Ru/Cu film has a sizeable ξ_DL of −2.2% and the insertion of Cu/Ru nanolayers at the interface can increase the ξ_DL value to −3.7%. The former could be attributed to the interface spin-orbit filtering effect and the latter may be further understood by the intrinsic contribution from the local electronic structure tuning due to the lattice distortion near the interface. A large effective spin Hall conductivity is achieved to be (3~5)×10^5 ℏ/2eΩ^(−1)m^(−1) in the epitaxial Ru/Cu hybrid nanolayers, which is in the same range as that of platinum. This work indicates that the interfacial control with hybrid nanolayer structures can extend the SOT-based materials to highly conductive metals, even with weak spin-orbit interactions, toward high stability, low cost, and low energy consumption for spintronic applications.

The orbital angular momentum is an electron’s essential degree of freedom and provides an alternative opportunity for the further development of spintronics. Recent studies suggest orbital transport as a potential tool to realize practical and highly-efficient spin manipulation with diverse material classes. Nevertheless, utilization of the orbital transport remains a challenging issue considering that the orbital transport often bares distinctive properties to the spin transport. Here we study the role of oxygen atom accumulation on the orbital transport in CoFe/Cu/Al2O3 ultrathin structures. By varying the type of oxygen accumulation, we revealed that the gradient of the oxygen accumulation nearby the CoFe/Cu interface can be a crucial factor of the orbital transport, modulating the orbital torque by a factor of about ~3. Our finding will encourage to realize efficient and versatile utilization of orbital transport for nano-spintronic devices.

We theoretically study the tunnel magnetoresistance (TMR) effect in (111)-oriented magnetic tunnel junctions (MTJs) with SrTiO$_{3}$ barriers, Co/SrTiO$_{3}$/Co(111) and Ni/SrTiO$_{3}$/Ni(111). Our analysis combining the first-principles calculation and the Landauer formula shows that the Co-based MTJ has a high TMR ratio over 500%, while the Ni-based MTJ has a smaller value (290%). Since the in-plane lattice periodicity of SrTiO$_{3}$ is about twice that of the primitive cell of fcc Co (Ni), the original bands of Co (Ni) are folded in the $k_x$-$k_y$ plane corresponding to the $ab$ plane of the MTJ supercell. We find that this band folding gives a half-metallic band structure in the $\Lambda_1$ state of Co (Ni) and the coherent tunneling of such a half-metallic $\Lambda_1$ state yields a high TMR ratio. We also reveal that the difference in the TMR ratio between the Co- and Ni-based MTJs can be understood by different $s$-orbital weights in the $\Lambda_1$ band at the Fermi level., Comment: 7 pages, 5 figures, 3 tables

Human induced pluripotent stem (iPS) cell-derived hepatocyte-like cells (HLCs) are expected to replace primary human hepatocytes as a new stable source of functional hepatocytes in various medical applications. However, the hepatic functions of HLCs are still low and it takes a long time to differentiate them from human iPS cells. Furthermore, HLCs have very low proliferative capacity and are difficult to be passaged due to loss of hepatic functions after reseeding. To overcome these problems, we attempted to develop a technology to dissociate, cryopreserve, and reseed HLCs in this study. By adding epithelial-mesenchymal transition inhibitors and optimizing the cell dissociation time, we have developed a method for passaging HLCs without loss of their functions. After passage, HLCs showed a hepatocyte-like polygonal cell morphology and expressed major hepatocyte marker proteins such as albumin and cytochrome P450 3A4 (CYP3A4). In addition, the HLCs had low-density lipoprotein uptake and glycogen storage capacity. The HLCs also showed higher CYP3A4 activity and increased gene expression levels of major hepatocyte markers after passage compared to before passage. Finally, they maintained their functions even after their cryopreservation and re-culture. By applying this technology, it will be possible to provide ready-to-use availability of cryopreserved HLCs for drug discovery research.

The coupling of single crystal diamond (SCD) micro-electromechanical systems (MEMS) through with a functional hetero-material provides the strategy to develop diamond MEMS sensors. Here a noncontact magnetic sensor based on SCD MEMS resonance system functionalized with a boron-doped FeGa (FeGaB) thin film owning excellent magneto-strictive properties on diamond is demonstrated to improve the magnetic sensitivity. The amorphous FeGaB thin film is beneficial for high magnetic sensing performance. The FeGaB/Ti/SCD MEMS magnetic sensor exhibits magnetic sensitivity of as high as 152.1 Hz/mT, which is over four times of those of FeGa/Ti/SCD MEMS magnetic sensors. The derivative of the Young’s modulus change with magnetic field (dE/dH) reaches a maximum value of 4.5 GPa/mT at 1.77 mT. By tailoring the magnetic properties with impurity dopant, one can markedly improve the sensitivity of the diamond MEMS magnetic sensitivity toward satisfying the figure-of-merits of ultra-high sensitivity, low noise level and high-reliability magnetic field operation.

We demonstrate tunnel magnetoresistance (TMR) ratios of up to 631% at room temperature (RT) using CoFe/MgO/CoFe(001) epitaxial magnetic tunnel junctions (MTJs). The TMR ratio increased up to 1143% at 10 K. The large TMR ratios resulted from fine-tuning of atomic-scale structures of the MTJs, such as crystallographic orientations and MgO interface oxidation by interface insertion of ultrathin CoFe and Mg layers, which are expected to enhance the well-known Δ1 coherent tunneling transport. Interestingly, the TMR oscillation effect, which is not covered by the standard coherent tunneling theory, also became significant. A 0.32-nm period TMR oscillation with increasing MgO thickness dominates the transport in a wide range of MgO thicknesses; the peak-to-valley difference of the TMR oscillation exceeds 140% at RT, which is attributed to the appearance of large oscillatory components in the resistance area product.

Spinel MgAl2O4 and family oxides are emerging barrier materials useful for magnetic tunnel junctions (MTJs). We report large tunnel magnetoresistance (TMR) ratios up to 429% at room temperature (RT) and 1,034% at 10 K in a Fe/MgAl2O4/Fe(001)-based MTJ prepared using electron-beam evaporation of Mg4Al-Ox. Resistance oscillations with a MTJ barrier thickness of 0.3-nm were significantly enhanced compared to those of a Fe/MgO/Fe(001) MTJ, resulting in a large TMR oscillation peak-to-valley difference of 125% at RT. The differential conductance spectra were symmetric with bias polarity, and the spectrum in the parallel magnetization state at low temperature demonstrate significant peaks within broad local minima at |0.2-0.6| V, indicating improved barrier interfaces by the Mg4Al-Ox barrier. This study demonstrates that TMR ratios in Fe(001)-MTJs can still be improved., 14 pages, 1 table, 4 figures

Green materials for electron spin manipulation are essential for common spintronic applications. Recent studies have documented the efficient generation of spin torque using spin-orbit interactions (SOIs); however, SOI use relies on the employment of rare metals such as platinum. Here, we demonstrate that a nanometre-thick gradient from silicon to aluminium, which consists of readily available elements from earth resources, can produce a spin torque over three times as large as that of platinum, despite the weak SOI of these compositions. The spin-torque efficiency can be improved by decreasing the thickness of the gradient, while a sharp interface was not found to increase the spin torque. Moreover, the electric conductivity of the gradient material can be up to twice as large as that of platinum, which provides a way to reduce Joule heating losses and signal delays in spintronic device circuits. Our findings represent a pathway for sustainable spin manipulation.

International audience; This work investigates the thermal expansion behaviors of Fe30Co30Ni30Cr10-xMnx High Entropy Alloys (HEAs) (x = 0, 5, 10 at.%) from 400 K to 1200 K. Interestingly, comparing to that of Cantor alloy, a decrease in Cr and Mn in Co–Cr–Fe–Mn–Ni system could significantly decrease the thermal expansion coefficient by 45.2%; Fe30Co30Ni30Cr10-xMnx (x = 0, 5, 10) also showed an abrupt change in thermal expansion behaviors similar to that of Invar alloys. Experimental and theoretical analysis suggest the abrupt change in thermal expansion behaviors of these HEAs were associated with the transition from ferromagnetism to paramagnetism, and these alloys appear to exhibit the dimensional stability of the Invar effect. Since the Invar effect is related to ferromagnetic properties, the amount of Cr and Mn in the HEAs would influence the suppression of thermal expansion due to different intensity of anti-ferromagnetic coupling effect. This research contributes to the understanding of the thermal expansion behaviors of Co–Cr–Fe–Mn–Ni high entropy alloys and the effects of antiferromagnetic elements

We investigate the effects of off-stoichiometric compositional variations from the Co2Fe(Ga0.5Ge0.5) (CFGG) full-Heusler alloy on its half-metallic electronic structure. First-principles calculations predict that the Co antisite defects that occupy Fe-sites (CoFe) lead to a finite DOS in the half-metallic gap of CFGG. Fe antisites defects in Co-sites (FeCo) introduced by excessing Fe composition, which could suppress the formation of CoFe, preserves the half-metallic gap but reduces spin polarization because the Fermi level shifts to the lower energy. We found that, in Fe-excess CFGG, Ge-excess has an important role to enhance the spin polarization by lifting up the Fermi level position and suppressing the formation of CoFe. To confirm the effect of the Fe and Ge-excess off-stoichiometric composition on spin polarization and phase-purity experimentally, we fabricated CFGG epitaxial thin films with various composition ratios (Co2− αFe1+ α) (Ga1− βGe β)1+ γ with small positive γ (=0.09–0.29). It turns out that Co1.75Ge or Fe1.7Ge secondary phase often forms in the films for [Formula: see text] in Fe-deficient [Formula: see text] and excess [Formula: see text] compositions. This secondary phase can be suppressed by tuning the Ge and Fe compositions, and the L21-phase pure film was found in Co39.4Fe29.3Ga13.4Ge17.9 [Formula: see text]. The measurements of conventional magnetoresistance effects qualitatively indicate higher spin polarization in the Co39.4Fe29.3Ga13.4Ge17.9 film compared to other Co-excess and Ge-deficient films, which evidences the benefit to make Fe- and Ge-excess off-stoichiometric CFGG for obtaining the half-metallic nature of CFGG.

After the demonstration of the giant tunnel magnetoresistance (TMR) ratios at room temperature (RT) using a crystalline MgO barrier based magnetic tunnel junctions (MTJs) in 2004 [1] , [2] , an application range of spintronic devices, including read-heads of hard disk drives (HDDs) and cells of magnetoresistive random access memories (MRAMs), has been significantly boosted. Use of MgO barriers enabled to obtain large electric output from MTJ structures since a large TMR ratio over 100% can be easily achieved due to the ∆ 1 band preferential coherent tunneling mechanism [3] . Fe/MgO/Fe(001) is known as one of the most basic structures exhibiting the giant TMR effect [2] . The structure is very simple, and thus many theoretical calculations have been demonstrated so far [3] , [4] . However, experimental TMR ratios (180~220% at RT and 290-370% at low temperature) are much smaller than those of the predictions like >1,000%. In order to create novel MTJ-based applications, such as high-capacity MRAMs, magnetic logics, and brain-morphic devices, further improvement in an experimental TMR ratio is needed. Especially, it should be essential to understand the origin of the TMR gap between experiments and theories. In this study, we revisited the simplest "Fe/MgO/Fe(001)" MTJ to obtain much larger TMR ratios by careful tuning of growth conditions for all the layers, combining sputtering and electron-beam evaporation, and MgO barrier interface modifications [5] .

Human induced pluripotent stem (iPS) cell-derived hepatocyte-like cells (iPS-HLCs) are expected to be applicable to large-scale in vitro hepatotoxicity screening systems. Accordingly, methods for generating HLCs from human iPS cells have been improved over the past decade. However, although human hepatocytes have zone-specific characteristics in vivo, there is currently no technique to generate zone-specific HLCs from human iPS cells. Therefore, to generate HLCs with zone-specific properties from human iPS cells, we cultured iPS-HLCs using a parenchymal or nonparenchymal cell-conditioned medium (CM). The results showed that urea production and gluconeogenesis capacity in iPS-HLCs were increased by culturing with cholangiocyte-CM, and glutamine production and drug metabolism capacity in iPS-HLCs were increased by culturing with hepatocyte-CM. It was thus clarified that iPS-HLCs acquire zone 1 hepatocyte-like properties by culturing with cholangiocyte-CM and that iPS-HLCs acquire zone 3 hepatocyte-like properties by culturing with hepatocyte-CM. In addition, we found that WNT inhibitory factor-1 secreted from cholangiocytes, and WNT7B and WNT8B secreted from hepatocytes play important roles in the zone-specific conversion of iPS-HLCs. We hope that our findings will facilitate the application of iPS-HLCs to drug discovery research.

Heusler alloys are theoretically predicted to become half-metals at room temperature (RT). The advantages of using these alloys are good lattice matching with major substrates, high Curie temperature above RT and intermetallic controllability for spin density of states at the Fermi energy level. The alloys are categorised into half- and full-Heusler alloys depending upon the crystalline structures, each being discussed both experimentally and theoretically. Fundamental properties of ferromagnetic Heusler alloys are described. Both structural and magnetic characterisations on an atomic scale are typically carried out in order to prove the half-metallicity at RT. Atomic ordering in the films is directly observed by X-ray diffraction and is also indirectly probed via the temperature dependence of electrical resistivity. Element specific magnetic moments and spin polarisation of the Heusler alloy films are directly measured using X-ray magnetic circular dichroism and Andreev reflection, respectively. By employing these ferromagnetic alloy films in a spintronic device, efficient spin injection into a non-magnetic material and large magnetoresistance are also discussed. Fundamental properties of antiferromagnetic Heusler alloys are then described. Both structural and magnetic characterisations on an atomic scale are shown. Atomic ordering in the Heusler alloy films is indirectly measured by the temperature dependence of electrical resistivity. Antiferromagnetic configurations are directly imaged by X-ray magnetic linear dichroism and polarised neutron reflection. The applications of the antiferromagnetic Heusler alloy films are also explained. The other non-magnetic Heusler alloys are listed. A brief summary is provided at the end of this review., Graphical abstract

We have studied current induced magnetization switching in W/CoFeB/MgO based three terminal magnetic tunnel junctions. The switching driven by spin—orbit torque (SOT) is evaluated in the so-called type-Y structure, in which the magnetic easy-axis of the CoFeB layer lies in the film plane and is orthogonal to the current flow. The effective spin Hall angle estimated from the bias field dependence of critical current (Ic) is ~ 0.07. The field and current dependence of the switching probability are studied. The field and DC current induced switching can be described using a model based on thermally assisted magnetization switching. In contrast, the 50 ns long pulse current dependence of the switching probability shows significant deviation from the model, even if contribution from the field-like torque is included. The deviation is particularly evident when the threshold switching current is larger. These results show that conventional thermally assisted magnetization switching model cannot be used to describe SOT induced switching using short current pulses.

The origin of the interfacial perpendicular magnetic anisotropy (PMA) induced in the ultrathin Fe layer on the Au(111) surface was examined using synchrotron-radiation-based M\"ossbauer spectroscopy (MS), x-ray magnetic circular dichroism (XMCD), and angle-resolved photoemission spectroscopy (ARPES). To probe the detailed interfacial electronic structure of orbital hybridization between the Fe $3d$ and Au $6p$ bands, we detected the interfacial proximity effect, which modulates the valence-band electronic structure of Fe, resulting in PMA. MS and XMCD measurements were used to detect the interfacial magnetic structure and anisotropy in orbital magnetic moments, respectively. In situ ARPES also confirms the initial growth of Fe on large spin-orbit coupled surface Shockley states under Au(111) modulated electronic states in the vicinity of the Fermi level. This suggests that PMA in the Fe/Au(111) interface originates from the cooperation effects among the spin, orbital magnetic moments in Fe, and large spin-orbit coupling in Au. These findings pave the way to develop interfacial PMA using $p\text{\ensuremath{-}}d$ hybridization with a large spin-orbit interaction.

We study the tunnel magnetoresistance (TMR) effect and magnetocrystalline anisotropy in a series of magnetic tunnel junctions (MTJs) with $L1_1$-ordered fcc ferromagnetic alloys and MgO barrier along the [111] direction. Considering the (111)-oriented MTJs with different $L1_1$ alloys, we calculate their TMR ratios and magnetocrystalline anisotropies on the basis of the first-principles calculations. The analysis shows that the MTJs with Co-based alloys (CoNi, CoPt, and CoPd) have high TMR ratios over 2000$\%$. These MTJs have energetically favored Co-O interfaces where interfacial antibonding between Co $d$ and O $p$ states is formed around the Fermi level. We find that the resonant tunneling of the antibonding states, called the interface resonant tunneling, is the origin of the obtained high TMR ratios. Our calculation of the magnetocrystalline anisotropy shows that many $L1_1$ alloys have large perpendicular magnetic anisotropy (PMA). In particular, CoPt has the largest value of anisotropy energy $K_{\rm u} \approx 10\,{\rm MJ/m^3}$. We further conduct a perturbation analysis of the PMA with respect to the spin-orbit interaction and reveal that the large PMA in CoPt and CoNi mainly originates from spin-conserving perturbation processes around the Fermi level., Comment: 11 pages, 9 figures, 2 tables

Quantum-well (QW) devices have been extensively investigated in semiconductor structures. More recently, spin-polarized QWs were integrated into magnetic tunnel junctions (MTJs). In this Letter, we demonstrate the spin-based control of the quantized states in iron $3d$-band QWs, as observed in experiments and theoretical calculations. We find that the magnetization rotation in the Fe QWs significantly shifts the QW quantization levels, which modulate the resonant-tunneling current in MTJs, resulting in a tunneling anisotropic magnetoresistance (TAMR) effect of QWs. This QW-TAMR effect is sizable compared with other types of TAMR effect, and it is present above room temperature. In a QW MTJ of $\mathrm{Cr}/\mathrm{Fe}/{\mathrm{MgAl}}_{2}{\mathrm{O}}_{4}/\mathrm{top}$ electrode, where the QW is formed by a mismatch between Cr and Fe in the $d$ band with ${\mathrm{\ensuremath{\Delta}}}_{1}$ symmetry, a QW-TAMR ratio of up to 5.4% was observed at 5 K, which persisted to 1.2% even at 380 K. The magnetic control of QW transport can open new applications for spin-coupled optoelectronic devices, ultrathin sensors, and memory.

Spin-1 chiral semimetal is a new state of quantum matter hosting unconventional chiral fermions that extend beyond the common Dirac and Weyl fermions. B20-type CoSi is a prototypal material that accommodates such an exotic quasiparticle. To date, the spin transport properties in the spin-1 chiral semimetals, have not been explored yet. In this work, we fabricated B20-CoSi thin films on sapphire c-plane substrates by magnetron sputtering and studied the spin Hall effect (SHE) by combining experiments and first-principles calculations. The SHE of CoSi using CoSi/CoFeB/MgO heterostructures was investigated via spin Hall magnetoresistance and harmonic Hall measurements. First-principles calculations yield an intrinsic spin Hall conductivity (SHC) at the Fermi level that is consistent with the experiments and reveal its unique Fermi-energy dependence. Unlike the Dirac and Weyl fermion-mediated Hall conductivities that exhibit a peak-like structure centering around the topological node, SHC of B20-CoSi is odd and crosses zero at the node with two antisymmetric local extrema of opposite sign situated below and above in energy. Hybridization between Co d-Si p orbitals and spin-orbit coupling are essential for the SHC, despite the small (~1%) weight of Si p-orbital near the Fermi level. This work expands the horizon of topological spintronics and highlights the importance of Fermi-level tuning in order to fully exploit the topology of spin-1 chiral fermions for spin current generation., Comment: 24 pages, 6 figures

The coexistence of a low magnetic Gilbert damping constant and large perpendicular magnetic anisotropy (PMA) in ferromagnetic thin films is critical for high-speed and energy-efficient spintronics devices. To clarify the spin-resolved contributions of damping and PMA, a flat, lattice-matched interface is developed in an $\mathrm{Fe}$(0.7 nm)/${\mathrm{Mg}\mathrm{Al}}_{2}{\mathrm{O}}_{4}$(oxide)(3 nm) bi-layer film by varying the ex situ annealing temperature, which acts as a catalyst to vary the PMA energy densities according to the oxidation degree. Here, the optimized procedure for interface engineering is implemented to achieve an extremely low magnetic Gilbert damping constant (0.013) and a strong interfacial PMA energy $(0.8\phantom{\rule{0.1em}{0ex}}\mathrm{MJ}\phantom{\rule{0.1em}{0ex}}{\mathrm{m}}^{\ensuremath{-}3})$ for epitaxial thin films. By employing different interfacial atomic configurations in a first-principles calculation, this study explains the origin of the PMA energy and damping constant. The d(yz) and d(zx) orbitals of the interfacial $\mathrm{Fe}$ atoms in the minority-spin states play a role in the orbital moment and its anisotropy. Furthermore, the matrix elements between these two orbitals in the non-spin-flip term predominately contribute to damping. These detailed findings provide a clear insight into the development of materials with significantly improved PMA energies and low damping characteristics, thereby facilitating promising future spintronic applications.

Giant tunnel magnetoresistance (TMR) ratios of 417% at room temperature (RT) and 914% at 3 K were demonstrated in epitaxial Fe/MgO/Fe(001) exchanged-biased spin-valve magnetic tunnel junctions (MTJs) by tuning growth conditions for each layer, combining sputter deposition for the Fe layers, electron-beam evaporation of the MgO barrier, and barrier interface tuning. Clear TMR oscillation as a function of the MgO thickness with a large peak-to-valley difference of ~80% was observed when the layers were grown on a highly (001)-oriented Cr buffer layer. Specific features of the observed MTJs are symmetric differential conductance (dI/dV) spectra for the bias polarity and plateau-like deep local minima in dI/dV (parallel configuration) at |V| = 0.2~0.5 V. At 3K, fine structures with two dips emerge in the plateau-like dI/dV, reflecting highly coherent tunneling through the Fe/MgO/Fe. We also observed a 496% TMR ratio at RT by a 2.24-nm-thick-CoFe insertion at the bottom-Fe/MgO interface., 21 pages, 7 figures

$\mathrm{C}{\mathrm{o}}_{2}\mathrm{MnAl}$ has been predicted to have Weyl points near the Fermi level in $L{2}_{1}$-ordered structure, which is expected to give rise to exotic transverse transport properties such as large anomalous Hall (AHE) and Nernst effects (ANE) due to large Berry curvature. In this study, the effects of Fermi level position and atomic ordering on AHE and ANE in $\mathrm{C}{\mathrm{o}}_{2}\mathrm{MnA}{\mathrm{l}}_{1\ensuremath{-}x}\mathrm{S}{\mathrm{i}}_{x}$ were studied systematically. The $\mathrm{C}{\mathrm{o}}_{2}\mathrm{MnAl}$ film keeps $B2$-disordred structure regardless of annealing temperature, which results in much smaller anomalous Hall conductivity ${\ensuremath{\sigma}}_{xy}$ and transverse Peltier coefficient ${\ensuremath{\alpha}}_{xy}$ than those calculated for $L{2}_{1}$-ordered $\mathrm{C}{\mathrm{o}}_{2}\mathrm{MnAl}$. Our newly performed calculation of ${\ensuremath{\sigma}}_{xy}$ with taking $B2$ disordering into account well reproduces the experimental result; thus it was concluded that Berry curvature originating from the Weyl points is largely reduced by $B2$ disordering. It was also revealed Al substitution with Si shifts the position of the Fermi level and greatly improves the $L{2}_{1}$ atomic ordering, leading to strong enhancement of ${\ensuremath{\alpha}}_{xy}$, which also agreed with our theoretical calculation. The highest thermopower of ANE of 5.7 \ensuremath{\mu}V/K, which is comparable to the recent reports for $\mathrm{C}{\mathrm{o}}_{2}\mathrm{MnGa}$, was observed for $\mathrm{C}{\mathrm{o}}_{2}\mathrm{MnA}{\mathrm{l}}_{0.63}\mathrm{S}{\mathrm{i}}_{0.37}$ because of dominant contribution of ${\ensuremath{\alpha}}_{xy}$. This study clearly shows the importance of both Fermi level tuning and high atomic ordering for obtaining the effect of topological features in Co-based Heusler alloys on transverse transport properties.

We investigated the structure of 1-nm-thick Co2FeAl (CFA)/MgAl2O4 (MAO) epitaxial heterojunctions in order to understand the origin of perpendicular magnetic anisotropy (PMA). The CFA/MAO stacks were fabricated by plasma oxidation of Mg-Al grown on the CFA layer and subsequent post-annealing process. Before post-annealing (as-oxidized), the stack showed in-plane magnetization with poor crystallinity of the MAO layer. After post-annealing, the stack showed PMA accompanied by the improved crystallinity in the MAO layer, leading to the formation of a lattice-matched CFA/MAO(001) epitaxial interface. These behaviors indicate that the crystallization of the MAO layer is strongly promoted by atomic templating effect from a lattice-matched underlayer. In addition, we also found that this MAO crystallization effectively enhanced PMA at the interface. At the same time, significant Al atomic diffusion from CFA to MAO was confirmed. This Al diffusion was observed in the as-oxidized stack, and this was further promoted by the post-annealing. Therefore, the strong PMA at the CFA/MAO interfaces is attributed to (i) the reduced in-plane magnetocrystalline anisotropy due to the lattice-matching and (ii) the promoted hybridization between Fe and O orbitals due to the Al re-distribution near the interface. These results include important findings for constructing high performance perpendicularly-magnetized magnetic tunnel junctions for non-volatile magnetic memory applications.

In this work, a metastable face-centered cubic High Entropy Alloy (HEA) Fe35.0Co28.7Ni24.8Cr1.1Al1.3V4.5Ti1.2Nb2.8Si0.6 was found to exhibit significantly suppressed thermal expansion coefficient (6.0 ppm/K) and stable Young's modulus over a wide temperature range. Experimental and theoretical analyses suggest that both Invar and Elinvar effects were present; in addition, the metastability of this alloy with respect to the first-order phase transition and the magnetic second-order phase transition led to abrupt changes in thermal expansion behavior. The first-order phase transition was associated with the formation of a plate-like D019 phase. The magnetic second-order phase transition decreased the Invar effect and the Elinvar effect and resulted in a significant magnetic entropy difference (−3.12 J kg−1 K−1) in this HEA of interest.

The function of hepatocytes largely depends on their position in the liver lobule. Although the method of differentiating hepatocytes from human pluripotent stem cells has been largely improved over the past decade, there remains no technique for generating hepatocyte-like cells (HLCs) with zone-specific hepatic properties. In this study, we searched for the factors that promote acquisition of zone-specific properties of HLCs. Here, we identified that WNT7B and WNT8B secreted from hepatocytes and cholangiocytes play important roles in achieving perivenous zone-specific characteristics, such as the enhancement of glutamine secretion, citric acid cycle, cytochrome P450 (CYP) 1A2 metabolism, and CYP1A2 induction capacities. We also found that WNT inhibitory factor (WIF-1) secreted from cholangiocytes was necessary for achieving periportal zone-specific characteristics, such as the enhancement of urea secretion and gluconeogenesis capacities. Therefore, WNT signal modulators secreted from hepatocytes or cholangiocytes conferred zone-specific hepatic properties onto HLCs.

International audience; We report for the first time the thermoelectric properties of CuCr2-xSbxS4 (0.22

This study reports the magnetization switching induced by spin-orbit torque (SOT) from the spin current generated in Co2MnGa magnetic Weyl semimetal (WSM) thin films. We deposited epitaxial Co2MnGa thin films with highly B2-ordered structure on MgO(001) substrates. The SOT was characterized by harmonic Hall measurements in a Co2MnGa/Ti/CoFeB heterostructure and a relatively large spin Hall efficiency of -7.8% was obtained.The SOT-induced magnetization switching of the perpendicularly magnetized CoFeB layer was further demonstrated using the structure. The symmetry of second harmonic signals, thickness dependence of spin Hall efficiency, and shift of anomalous Hall loops under applied currents were also investigated. This study not only contributes to the understanding of the mechanisms of spin-current generation from magnetic-WSM-based heterostructures, but also paves a way for the applications of magnetic WSMs in spintronic devices., 15 pages, 4 figures

We report on the tunnel magnetoresistance (TMR) effect of perpendicular magnetic tunnel junctions (p-MTJs) composed of a ferromagnetic antiperovskite MnGaN film with perpendicular magnetic anisotropy. The p-MTJ multilayer stack with MnGaN/Mg/MgO/Fe/CoFeB was used to control the MgO interface conditions by the Mg and Fe insertion layers. The Mg insertion under the MgO barrier enhanced the perpendicular anisotropy of the top Fe/CoFeB layers with post-annealing process, and thus nearly perfect perpendicular magnetization was realized. A perpendicular TMR ratio up to 3.7% $\sim 3.8$ % was obtained at room temperature. The obtained low TMR ratio is mainly attributed to the imperfect MgO barrier, which includes many lattice-misfit dislocations at the MnGaN/MgO interface due to the large lattice mismatch of 8%. This paper suggests that improving the interface state and reducing the lattice mismatch will be required to observe a higher perpendicular TMR ratio using an MnGaN electrode.

Hepatocyte-like cells differentiated from human iPS cells (human iPS-HLCs) are expected to be utilized in drug development and research. However, recent hepatic characterization of human iPS-HLCs showed that these cells resemble fetal hepatocytes rather than adult hepatocytes. Therefore, in this study, we aimed to develop a method to enhance the hepatic function of human iPS-HLCs. Because the gene expression levels of the hepatic transcription factors (activating transcription factor 5 (ATF5), CCAAT/enhancer-binding protein alpha (c/EBPα), and prospero homeobox protein 1 (PROX1)) in adult liver were significantly higher than those in human iPS-HLCs and fetal liver, we expected that the hepatic functions of human iPS-HLCs could be enhanced by adenovirus (Ad) vector-mediated ATF5, c/EBPα, and PROX1 transduction. The gene expression levels of cytochrome P450 (CYP) 2C9, 2E1, alpha-1 antitrypsin, transthyretin, Na+/taurocholate cotransporting polypeptide, and uridine diphosphate glucuronosyl transferase 1A1 and protein expression levels of CYP2C9 and CYP2E1 were upregulated by ATF5, c/EBPα, and PROX1 transduction. These results suggest that the hepatic functions of the human iPS-HLCs could be enhanced by ATF5, c/EBPα, and PROX1 transduction. Our findings would be useful for the hepatic maturation of human iPS-HLCs.