Half-Metallic Properties and Stability of Ferromagnetic State in the Full-Heusler Alloys (Fe<I><SUB>x</SUB></I>Ru<SUB>1&minus;<I>x</I></SUB>)<SUB>2</SUB>CrSi (0&le;<I>x</I>&le;1)

Abstract

We investigate the half-metallic properties and the stability of the ferromagnetic state in the alloys (Fe x Ru 1Àx ) 2 CrSi (0 x 1) with orderly and disorderly atomic arrangement based on the Heusler structure. It is predicted from the electronic structures that the ordered alloys are half-metals in the range of 1=3 < x < 3=4 and ferromagnets with high spin polarization in the range of 3=4 x 1. However, in the ferromagnetic state, the atomic arrangement with the Fe-Cr disorder tends to be energetically more favorable than the orderly arrangement, and the Fe-Cr disorder decreases the spin polarization of the ordered alloys. This is attributed to the fact that occupation of Cr sites by Fe destroys the gap near the Fermi energy in the minority spin state. But, because the Fe-Cr disorder shows a tendency to keep the spin polarization high as x increases, it is deduced that (Fe x Ru 1Àx ) 2 CrSi are materials with high spin polarization if x is high.

Magnetic and atomic order in the potential half metallic ferromagnets Ru2−xFexCrGe

“…The prediction on theoretical grounds of ideal half metallic ferromagnetism in Ru 2−x Fe x CrGe motivated a recent experimental study of a series of single phase alloys with 0.25 x 1.7 [9,10]. The linear decrease in lattice parameter with increasing x (figure 2) was taken to show that the Fe atoms enter the lattice sites randomly [13].…”

“…Recent band structure calculations suggest that at some compositions the new Heusler alloy series Ru 2−x Fe x CrZ (Z = Si, Ge) should be ideal half metallic ferromagnets with a large density of states in the majority spin states at the Fermi level [9,10]. The calculations predict an integral ground state moment of 2 μ B almost independent of Fe concentration.…”

Low-temperature magnetic properties of Heusler compoundsRu2−xFexCrSi<

“…[3][4][5] In a theoretical study, it was pointed out that Ru 2−x Fe x CrSi is a strong candidate material in which the half metallicity is preserved in the presence of higher level defects and randomness of the crystalline structure. 6 Hiroi et al [7][8][9] synthesized Ru 2−x Fe x CrSi compounds over a wide range of x, and investigated their transport and magnetic properties. For 1.4Յ x Ͻ 2.0, Ru 2−x Fe x CrSi shows ferromagnetic transition at a Curie temperature T C ϳ 500 K. With x decreasing from x ϳ 1.4, T C decreases linearly, and the system becomes antiferromagnetic below x = 0.2.…”