Theoretical prediction and experimental study of a ferromagnetic shape memory alloy: Ga_2MnNi

We predict the existence of a new ferromagnetic shape memory alloy Ga_2MnNi using density functional theory. The martensitic start temperature (T_M) is found to be approximately proportional to the stabilization energy of the martensitic phase (deltaE_tot) for different shape memory alloys. Experimental studies performed to verify the theoretical results show that Ga_2MnNi is ferromagnetic at room temperature and the T_M and T_C are 780K and 330K, respectively. Both from theory and experiment, the martensitic transition is found to be volume conserving that is indicative of shape memory behavior.Comment: 11 pages, 3 figure

Magnetic behavior of nano crystals of a spin-chain system, Ca3Co2O6: Absence of multiple steps in the low temperature isothermal magnetization

We report that the major features in the temperature dependence of dc and ac magnetization of a well-known spin-chain compound, Ca3Co2O6, which has been known to exhibit two complex magnetic transitions due to geometrical frustration (one near 24 K and the other near 10 K), are found to be qualitatively unaffected in its nano form synthesized by high-energy ball-milling. However, the multiple steps in isothermal magnetization - a topic of current interest in low-dimensional systems - known for the bulk form well below 10 K is absent in the nano particles. We believe that this finding will be useful to the understanding of the 'step' magnetization behavior of such spin-chain systems.Comment: Phys. Rev. B (Rapid Communications), in pres

The Mechanism of Ni-Assisted GaN Nanowire Growth

Despite the numerous reports on the metal-catalyzed growth of GaN nanowires, the mechanism of growth is not well understood. Our study of the nickel-assisted growth of GaN nanowires using metalorganic chemical vapor deposition provides key insights into this process. From a comprehensive study of over 130 nanowires, we observe that as a function of thickness, the length of the nanowires initially increases and then decreases. We attribute this to an interplay between the Gibbs–Thomson effect dominant in very thin nanowires and a diffusion induced growth mode at larger thickness. We also investigate the alloy composition of the Ni–Ga catalyst particle for over 60 nanowires using energy dispersive X-ray spectroscopy, which along with data from electron energy loss spectroscopy and high resolution transmission electron microscopy suggests the composition to be Ni₂Ga₃. At the nanowire growth temperature, this alloy cannot be a liquid, even taking into account melting point depression in nanoparticles. We hence conclude that Ni-assisted GaN nanowire growth proceeds via a vapor–solid–solid mechanism instead of the conventional vapor–liquid–solid mechanism

A model of simplification: the ways in which teachers simplify learning materials

The production of simplified language materials (SLMs) is a widespread practitioner response to delivering a curriculum to a diverse student population across mainstream settings. This paper examines the approaches of two groups of teachers and support staff in producing SLMs. It firstly reports on SLMs produced by 33 practitioners, identifying four main approaches. It then surveys 43 practitioners to test the reliability of these identified approaches. It offers a conceptual framework for describing SLMs and exploring their possible efficacy, highlighting the need to examine SLMs within the class context and their value as a tool of educational engagement. [ABSTRACT FROM AUTHOR