Long-Range Orbital Transport in Ferromagnets

While it is often assumed that the orbital transport is short-ranged due to strong crystal field potential and orbital quenching, we show that orbital propagation can be remarkably long-ranged in ferromagnets. In contrast to spin transport, which exhibits an oscillatory decaying behavior by spin dephasing, the injected orbital angular momentum does not oscillate and decays slowly. This unusual feature is attributed to nearly degenerate states in $\mathbf{k}$-space, which form hot-spots for the intrinsic orbital response. We demonstrate this in a bilayer consisting of a nonmagnet and a ferromagnet, where the orbital Hall current is injected from a nonmagnet into a ferromagnet. Interaction of the orbital Hall current with the magnetization in the ferromagnet results in an intrinsic response of the orbital angular momentum which propagates far beyond the spin dephasing length. This gives rise to a distinct type of orbital torque on the magnetization, increasing with the thickness of the ferromagnet. Such behavior may serve as critical long-sought evidence of orbital transport to be directly tested in experiments. Our findings open the possibility of using long-range orbital transport in orbitronic device applications

An Array of Ferromagnetic Nanoislands Nondestructively Patterned <i>via</i> a Local Phase Transformation by Low-Energy Proton Irradiation

Low-energy proton irradiation was applied to pattern an array of metallic, ferromagnetic nanoislands through the local phase transformation of an oxidic, paramagnetic phase in a complex superlattice composed of repetitions of an oxidic and metallic layer. The irradiation inflicted minimal damage on the structure, resulting in the absence of unwanted defects and side effects. This nondestructive pattern transfer was clearly confirmed by the contrast between irradiated and unirradiated regions in electrical, chemical, and magnetic images. Simulation based on the magnetic properties suggests that this low-energy proton irradiation can nondestructively pattern an array of ferromagnetic islands with 8.2 nm in diameter and 7.4 nm in spacing between islands, which means it can achieve an areal density of ∼3 Tb/in.² with a thermal stability of over 80 <i>k</i>_B<i>T</i>. Such an array is strong enough to overcome the so-called superparamagnetism limit in magnetic recording. The attributes demonstrated here corroborate that proton irradiation can be applied to design and pattern devices on a nanometer scale not only for magnetic but also for electric and optical materials systems in all such systems in which a local phase transformation is available

Leukemia inhibitory factor and its receptor: expression and regulation in the porcine endometrium throughout the estrous cycle and pregnancy

Objective Leukemia inhibitory factor (LIF) binds to a heterodimeric receptor composed of LIF receptor (LIFR) and glycoprotein 130 (GP130) to transmit signals into the cell. LIF plays an important role in reproduction by regulating immune response, decidualization, and implantation in several species. However, the expression of LIF and LIFR in the endometrium throughout the estrous cycle and pregnancy in pigs is not fully understood. Methods We analyzed the expression of LIF and LIFR in the endometrium on days 0 (estrus), 3, 6, 9, 12, 15, and 18 of the estrous cycle, and days 12, 15, 30, 60, 90, and 114 of pregnancy, in conceptuses on days 12 and 15, and in chorioallantoic tissues on days 30, 60, 90, and 114 of pregnancy in pigs. We also determined the effects of estrogen and progesterone on the expression of LIF and LIFR in endometrial tissues. Results The expression of LIF increased in the endometrium during the late diestrus phase of the estrous cycle and during mid- to late- pregnancy, while the expression of LIFR increased during early pregnancy. The expression of LIF was induced by increasing doses of estrogen, whereas the expression of LIFR was induced by increasing doses of progesterone. Conclusion These results indicate that the expression of LIF and its receptor LIFR in the endometrium is regulated in a stage-specific manner during the estrous cycle and pregnancy, suggesting that LIF and its receptor signaling system may play critical roles in regulating endometrial function in pigs

The Influence of Capping Layers on Tunneling Magnetoresistance and Microstructure in CoFeB/MgO/CoFeB Magnetic Tunnel Junctions upon Annealing

This study investigates the effects of annealing on the tunnel magnetoresistance (TMR) ratio in CoFeB/MgO/CoFeB-based magnetic tunnel junctions (MTJs) with different capping layers and correlates them with microstructural changes. It is found that the capping layer plays an important role in determining the maximum TMR ratio and the corresponding annealing temperature (Tann). For a Pt capping layer, the TMR reaches ~95% at a Tann of 350 °C, then decreases upon a further increase in Tann. A microstructural analysis reveals that the low TMR is due to severe intermixing in the Pt/CoFeB layers. On the other hand, when introducing a Ta capping layer with suppressed diffusion into the CoFeB layer, the TMR continues to increase with Tann up to 400 °C, reaching ~250%. Our findings indicate that the proper selection of a capping layer can increase the annealing temperature of MTJs so that it becomes compatible with the complementary metal-oxide-semiconductor backend process

Improved Robustness against Magnetic Field in Spin–Orbit‐Torque‐Based Physical Unclonable Functions through Write‐Back Operation

Abstract Physical unclonable functions (PUFs), which exploit uncontrollable and unpredictable randomness of materials or devices, have been investigated as a hardware‐based security primitive owing to their robustness against adversarial attacks. Spin–orbit torque (SOT) switching is one of the promising techniques for PUF applications because it can provide randomness by the stochastic switching distribution of perpendicular magnetization. In this study, the improvement in the reliability of SOT‐based PUFs against external magnetic fields with write‐back operation (WBO) is demonstrated. A PUF consisting of 8 × 4 array Hall‐bar devices with a Ta/CoFeB/MgO structure is fabricated, where the random distribution of the SOT switching current serves as an entropy source. However, the information stored in the PUF is easily modified by the application of an external magnetic field. To improve the robustness against magnetic fields, a WBO is introduced that applies an additional current to saturate the magnetization in either the upward or downward direction depending on the magnetic state. As a result, the SOT‐based PUF maintains an entropy value close to unity under a magnetic field of up to the coercive field of the CoFeB layer. Furthermore, the WBO provides a digitalized output, which potentially reduces peripheral circuitry such as analog‐to‐digital converters

Secondhand smoke exposures in indoor public places in seven Asian countries

Exposure to secondhand smoke (SHS) is a major threat to public health. Asian countries having the highest smoking prevalence are seriously affected by SHS. The objective of the study was to measure SHS levels in hospitality venues in seven Asian countries and to compare the SHS exposure to the levels in Western countries. The study was carried out in four types of related hospitality venues (restaurant, café, bar/club and entertainment) in China, India, Japan, Korea, Malaysia, Pakistan and Sri Lanka. Real-time measurement of particulate matter of \u3c2.5microm aerodynamic diameter (PM(2.5)) was made during business hour using a handheld laser operated monitor. A total of 168 venues were measured in seven countries. The average indoor PM(2.5) level was 137microg/m(3), ranging from 46microg/m(3) in Malaysia to 207microg/m(3) in India. Bar/club had the highest PM(2.5) level of 191microg/m(3) and restaurants had the lowest PM(2.5) level of 92microg/m(3). The average indoor PM(2.5) level in smoking venues was 156micro/m(3), which was 3.6 times higher than non-smoking venues (43microg/m(3)). Indoor PM(2.5) levels were significantly associated with country, type of venue, smoking density and air exchange rate (p\u3c0.05). In the seven Asian countries, PM(2.5) levels were high due to SHS in public places. The current levels are comparable to the levels in Western countries before the adoption of smoke-free policy. Since Asian country has high prevalence of SHS in public places, there is an urgent need for comprehensive smoke-free regulation in Asian countries