an irreversible stirling heat pump cycle using ferromagnetic materials as a cyclic working substance is established. the influences of finite-rate heat transfer, heat leak, regeneration time, regenerative lossand the internal irreversibility on the cyclic performance of magnetic heat pumps are taken into account. on the basis of the thermodynamic properties of ferromagnetic materials, the perfo...

Using ab initio calculations we study the stability of Si-based cages and nanotubes stabilized by encapsulated transition metal atoms ~TMAs!. It is demonstrated that the stabilization of these cages and nanotubes as well as their magnetic properties are strongly guided by a delicate interplay between the attainable symmetry of the system and the d-band filling of the encapsulated TMA. As a resu...

The Hubbard model in the limit of infinite U is investigated within a projected slave fermion representation and following a previous work of the author and collaborators [1]. The stability of the Nagaoka’s phase with respect to a non vanishing concentration of holes (δh) is analyzed by envisaging the existence of a spin effective action for itinerant magnetism of the Hubbard model. It is consi...

Controlling tunneling properties through graphene vertical heterostructures provides advantages in achieving large conductance modulation which has been known as limitation in lateral graphene device structures. Despite of intensive research on graphene vertical heterosturctures for recent years, the potential of spintronics based on graphene vertical heterostructures remains relatively unexplo...

We present an efficient quantum algorithm for the exact evaluation of either the fully ferromagnetic or anti-ferromagnetic q-state Potts partition function Z for a family of graphs related to irreducible cyclic codes. This problem is related to the evaluation of the Jones and Tutte polynomials. We consider the connection between the weight enumerator polynomial from coding theory and Z and expl...

In this paper we present a study of magnetic order of quantum Heisenberg spins on pyrochlore type lattices: a lattice of corner sharing tetrahedra. We use the Cluster Variation Approximation with the tetrahedron as basic cluster. We find that in case of anti-ferromagnetic nearest–neighbour exchange there is no long–range spin order at any finite temperature for any spin s. For ferromagnetic exc...

Fe,,,Ni, with xs30 at.%, known as anti-Invar alloys, undergo mprtensitic transformations. Total energy calculations have shown that these alloys incorporate a strongly fluctuating magnetic moment in the fcc state. In order to undeixtand the relationship between the moment fluctuations and the martensitic transformation, we have investigated the magnetic moment in the paramagnetic fcc state of t...

The hot electron magnetotransport in a spin-valve transistor has been theoretically explored at finite temperatures. We have explored the parallel and anti-parallel collector current changing the relative spin orientation of the ferromagnetic layers at finite temperatures. In this model calculations, hot electron energy redistribution due to spatial inhomogeneity of Schottky barrier heights and...