Selection criteria for spintronic materials: Role of spin dependent band-width narrowing/broadening

Abstract

The selection of a material of a particular application in spintronics requires that criteria of half-metallic should be fulfilled. The stability with adequate cohesive energy of the systems plays an important role. Apart from stability, magnetic moment must be adequate to store the information along with the appropriate presence of conducting channels at Fermi energy to conduct. Recently we have established a bridge between the results obtained by density functional theory (DFT) with those from mean field theory in the case of monatomic chains of 3-d series of periodic table. We have found that in the systems with less than half filled band, the up spin channel contributes for conduction and in case of more than half filled band the down spin channel contributes in conduction, while other channel is responsible for maintaining the magnetic state. It has been observed that both the conditions of stabilized magnetic state and conduction are required for a good spintronic material. Therefore in case of available systems, the materials with more than half filled would be better from application point of view.Therefore, we have extended our previous study to 4-d and 5-d series of periodic table for systems with more than half filled band only i.e. 4-d elements (Ru, Rh, Pd) and 5-d elements (Os, Ir, Pt) in 1 dimension (1D: monatomic chain), 2 dimension (2D: monolayer) and 3 dimension (3D: bulk) in addition to 3-d elements (Fe, Co, Ni). The study establishes a fact that as magnetization changes, for more than half filled band, the bandwidth or conduction also changes in such a way that bandwidth of up spin decreases and for down spin increases. The study also verifies that, in these systems, the onset of magnetism as well as enhancement of magnetic moment in low dimensions are driven by the combined role of band splitting and band-narrowing/broadening of the individual spin bands.