We report observations of tunneling anisotropic magnetoresitance (TAMR) in vertical tunnel devices with a ferromagnetic multilayer-(Co/Pt) electrode and a non-magnetic Pt counter-electrode separated by an AlOx barrier. In stacks with the ferromagnetic electrode terminated by a Co film the TAMR magnitude saturates at 0.15% beyond which it shows only weak dependence on the magnetic field strength, bias voltage, and temperature. For ferromagnetic electrodes terminated by two monolayers of Pt we observe order(s) of magnitude enhancement of the TAMR and a strong dependence on field, temperature and bias. Discussion of experiments is based on relativistic ab initio calculations of magnetization orientation dependent densities of states of Co and Co/Pt model systems.PACS numbers: 85.75. Mm,75.45.+j,75.50.Cc Anisotropic magnetoresistance (AMR) sensors replaced in the early 1990s classical magneto-inductive coils in hard-drive readheads launching the era of spintronics. Their utility has, however, remained limited partly because the response of these ferromagnetic resistors to changes in magnetization orientation originates from generically subtle spin-orbit (SO) interaction effects [1]. Currently widely used giant magnetoresistance [2] and tunneling magnetoresistance (TMR) [3] elements comprising (at least) two magnetically decoupled ferromagnetic layers provided a remarkably elegant way of tying the magnetoresistance response directly to the ferromagnetic exchange splitting of the carrier bands without involving SO-coupling. Large magnetoresistances in these devices are, nevertheless, obtained at the expense of a significantly increased structure complexity, necessary to guarantee independent and different magnetization switching characteristics and spin-coherence of transport between the ferromagnetic layers.Studies of AMR effects [4,5,6,7] in ferromagnetic semiconductor tunneling devices showed that AMR response can in principle be huge and richer than TMR, with the magnitude and sign of the magnetoresistance dependent on the magnetic field orientation and electric fields. Subsequent theoretical work predicted [8] that the tunneling AMR (TAMR) effect is generic in ferromagnets with SO-coupling, including the high Curie temperature transition metal systems. A detailed investigation of the TAMR is therefore motivated both by its intricate relativistic quantum transport nature and by its potential in more versatile alternatives to current TMR devices which will not require two independently controlled ferromagnetic electrodes and spin-coherent tunneling.Experimental demonstration of the TAMR in a tunnel junction with a ferromagnetic metal electrode has recently been reported [9] in an epitaxial Fe/GaAs/Au stack. The observed TAMR in this structure is relatively small, bellow 0.5%, consistent with the weak SO-coupling in Fe. In this paper we present a study of vertical tunnel devices in which the ferromagnetic electrode comprises alternating Co and Pt films. We build upon the extensive literature [10,11,12,13,14,15] o...

Logic devices based on magnetism show promise for increasing computational efficiency while decreasing consumed power. They offer zero quiescent power and yet combine novel functions such as programmable logic operation and non-volatile built-in memory. However, practical efforts to adapt a magnetic device to logic suffer from a low signal-to-noise ratio and other performance attributes that are not adequate for logic gates. Rather than exploiting magnetoresistive effects that result from spin-dependent transport of carriers, we have approached the development of a magnetic logic device in a different way: we use the phenomenon of large magnetoresistance found in non-magnetic semiconductors in high electric fields. Here we report a device showing a strong diode characteristic that is highly sensitive to both the sign and the magnitude of an external magnetic field, offering a reversible change between two different characteristic states by the application of a magnetic field. This feature results from magnetic control of carrier generation and recombination in an InSb p-n bilayer channel. Simple circuits combining such elementary devices are fabricated and tested, and Boolean logic functions including AND, OR, NAND and NOR are performed. They are programmed dynamically by external electric or magnetic signals, demonstrating magnetic-field-controlled semiconductor reconfigurable logic at room temperature. This magnetic technology permits a new kind of spintronic device, characterized as a current switch rather than a voltage switch, and provides a simple and compact platform for non-volatile reconfigurable logic devices.

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Among two-dimensional (2D) layered van der Waals materials, ferromagnetic 2D materials can be useful for compact low-power spintronic applications. One promising candidate material is Fe3GeTe2 (FGT), which has a strong perpendicular magnetic anisotropy and relatively high Curie temperature. In this study, we confirmed that an oxide layer (O-FGT) naturally forms on top of exfoliated FGT and that an antiferromagnetic coupling (AFC) exists between FGT and O-FGT layers. From a first-principles calculation, oxide formation at the interface of each layer induces an AFC between the layers. An AFC causes a tailed hysteresis loop, where two-magnetization reversal curves are included, and a negative remanence magnetization at a certain temperature range.

The purpose of the present study was to determine the prevalence of excessive daytime sleepiness (EDS) and its associations with sleep habits, sleep problems, and school performance in high school students in South Korea. A total of 3871 students (2703 boys and 1168 girls with a mean age of 16.8 years and 16.9 years, respectively) aged 15-18 years in the 11th grade of high school completed a questionnaire that contained items about individual sociodemographic characteristics, sleep habits, and sleep-related problems. The overall prevalence of EDS was 15.9% (14.9% for boys and 18.2% for girls). Mean reported total sleep time was similar in EDS and non-EDS (6.4 ± 1.6 and 6.4 ± 1.3 h/day, respectively). The increased risk of EDS was related to perceived sleep insufficiency (P < 0.001), teeth grinding ≥4 days/week (P < 0.001), witnessed apnea ≥1-3 days/week (P < 0.01), nightmares ≥4 days/week (P < 0.05), low school performance (P < 0.01), and two or more insomnia symptoms (P < 0.05). Students with low school performance had a 60% excess in the odds of EDS compared to those whose school performance was high. These findings suggest that EDS is associated with multiple sleep-related factors in adolescents. Whether interventions to modify associated correlates can alter EDS warrants consideration, especially because it may also improve academic performance in high school students.

Habitual snoring is associated with cardiovascular morbidity and mortality, and metabolic abnormalities such as impaired glucose homeostasis. Many studies were performed in obese Western populations. The purpose of this study was to examine the association of habitual snoring with glucose and insulin metabolism in nonobese Korean men who were free of diabetes and hypertension. A total of 2,719 men ages 40-69 years from the Korean Health and Genome Study participated in this study. Information of snoring frequency was obtained by a questionnaire and glucose and insulin levels during oral glucose tolerance test were measured. Repeated measures analysis of variance detected significant differences in the changing patterns of glucose and insulin levels at 1 hour and 2 hours between habitual snorers and nonhabitual snorers, whereas there were no significant differences in fasting blood glucose and insulin levels. Multivariate logistic regression analyses revealed that habitual snoring was independently associated with elevated 1-hour and 2-hour glucose levels and a 2-hour insulin level, respectively. The present data suggest that habitual snoring may affect glucose-insulin metabolism, independent of diabetes and hypertension, even in nonobese Korean middle-age men. Further prospective studies are needed to examine the causal relationship between habitual snoring and insulin resistance or glucose intolerance.

A questionnaire survey was carried out to examine the sleep habits and excessive daytime sleepiness (EDS) of 3871 high school students with a mean age of 16.8 years in Korea. The results showed that mean total sleep time was 6.3 h/day for male students and 6.5 h/day for female students, which may be insufficient for adolescence during puberty. The overall prevalence of EDS (defined as an Epworth sleepiness scale score of > 10) was 15.9% (14.9% for boys and 18.2% for girls). The prevalence of EDS increased significantly ( P < 0.001) with a decline in school performance.

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