Gate-tunable black phosphorus spin valve with nanosecond spin lifetimes

Two-dimensional materials offer new opportunities for both fundamental science and technological applications, by exploiting the electron spin. While graphene is very promising for spin communication due to its extraordinary electron mobility, the lack of a band gap restricts its prospects for semiconducting spin devices such as spin diodes and bipolar spin transistors. The recent emergence of 2D semiconductors could help overcome this basic challenge. In this letter we report the first important step towards making 2D semiconductor spin devices. We have fabricated a spin valve based on ultra-thin (5 nm) semiconducting black phosphorus (bP), and established fundamental spin properties of this spin channel material which supports all electrical spin injection, transport, precession and detection up to room temperature (RT). Inserting a few layers of boron nitride between the ferromagnetic electrodes and bP alleviates the notorious conductivity mismatch problem and allows efficient electrical spin injection into an n-type bP. In the non-local spin valve geometry we measure Hanle spin precession and observe spin relaxation times as high as 4 ns, with spin relaxation lengths exceeding 6 um. Our experimental results are in a very good agreement with first-principles calculations and demonstrate that Elliott-Yafet spin relaxation mechanism is dominant. We also demonstrate that spin transport in ultra-thin bP depends strongly on the charge carrier concentration, and can be manipulated by the electric field effect

Predicting exercise behaviour in Iranian college students: utility of an integrated model of health behaviour based on the transtheoretical model and self-determination theory

Objective: The purpose of this study was to evaluate an integrated theoretical model of health behaviour based on constructs from the Transtheoretical Model (TTM) and Self-determination Theory (SDT). Design: Cross-sectional. Methods: Participants (N = 418) were students from five medical sciences universities located in northern Iran. Participants completed translated versions of Godin and Shephard’s Leisure Time Exercise Questionnaire (LTEQ) and another questionnaire which included a range of constructs from the TTM and SDT. Data were analyzed using bivariate correlation and structural equation modeling. Results: The relationships between exercise behaviour and all of the constructs from the TTM and SDT (except external regulation) were statistically significant. The modified model provided a good fit to the data and explained 82% of the variance in current exercise behaviour. All of the structural pathways, with the exception of pros and cons, were significant and positive. Conclusions: Study findings support the application of an integrated model of health behaviour combining constructs from the TTM and SDT to explain the exercise behaviour of Iranian college students