Melike Kaya

Magnetic and magnetocaloric properties of Ni43Mn46−xAlxIn11 (x = 0, 0.5 and 1.0)

A nearly parallel G2-manifold Y is a Riemannian 7-manifold whose cone C(Y ) = R>0 × Y has the holonomy group contained in Spin(7). In other words, it is a spin 7-manifold with a real Killing spinor. We have a special class of calibrated submanifolds called Cayley submanifolds in C(Y ). An associative submanifold in Y is a minimal 3submanifold whose cone is Cayley. We study its deformations, namely, Cayley cone deformations, explicitly when it is homogeneous in the 7sphere S.

Room temperature magnetocaloric effect in Pr1.75Sr1.25Mn2O7 double-layered perovskite manganite system

Abstract In this work, we have studied on double-layered perovskite (Ruddlesden–Popper) manganite structure in Pr1.75Sr1.25Mn2O7 synthesised by sol–gel method. The crystal structure of the double-layered perovskite is found as tetragonal from the X-ray diffraction analysis with I4/mmm space group. A high Curie temperature, TC = 305 K is observed from the temperature dependence of magnetisation measurement. The isothermal magnetisation curves showed that magnetic phase transition is second order due to the positive slope of the Arrott plots. Maximum magnetic entropy change (ΔSM) and adiabatic temperature change (ΔTad) values are calculated as 3.99 J kg−1 K−1 and 2.1 K under external magnetic field of 70 kOe, respectively. Since our double-layered perovskite manganite sample has desired TC value and relatively high ΔSM, it can be a potential candidate as a magnetocaloric material for room temperature magnetic cooling systems.

Effect of heat treatment procedure on magnetic and magnetocaloric properties of Ni43Mn46In11 melt spun ribbons

Abstract The effect of heat treatment on the structural, magnetic and magnetocaloric properties of Ni43Mn46In11 melt-spun ribbons was systematically investigated using X-ray powder diffraction (XRD), scanning electron microscope (SEM), atomic force microscope (AFM), magnetic force microscope (MFM) and magnetic measurements. From the XRD studies, tetragonal and cubic phases were detected at room temperature for as-spun, quenched and slow-cooled ribbons. Furthermore, it was observed, upon annealing martensite transition temperatures increased when compared to the as-spun ribbon. To avoid magnetic hysteresis losses in the vicinity of the structural transition region, the magnetic entropy changes-ΔS m of the investigated ribbons were evaluated from temperature-dependent magnetisation-M(T) curves on cooling for different applied magnetic fields. The maximum ΔS m value was found to be 6.79 J kg−1 K−1 for the quenched ribbon in the vicinity of structural transition region for a magnetic field change of 50 kOe.