The magnetization distributions in some Heusler alloys proposed as half-metallic ferromagnets

Abstract

The magnetization distributions in a series of ternary intermetallic compounds based on the composition Co2 YZ where Y is Ti, Mn or Fe and Z a subgroup-B element have been determined from polarized neutron diffraction measurements. Comparison of the magnetic structure factors with model calculations shows that the magnetization is associated principally with those atoms which in their elemental state are themselves magnetic. The observed deviations of the magnetic moment distributions from spherical symmetry have been used to deduce which of the 3d sub-bands are active at the Fermi energy. A small moment close to the limits of resolution is observed at some of the Z sites, together with a small delocalized moment which in most cases is negative. The results have been compared with the predictions of band models, which indicate that the Fermi level falls in a broad minimum in the minority-spin density of d states. Although the identity of the bands active at the Fermi surface is in broad agreement with predictions of band-structure calculations (Ishida S, Akazawa S, Kubo Y and Ishida J 1982 J. Phys. F: Met. Phys. 12 1111), the results suggest that there is a finite density of states in the minority-spin d band of manganese. Hence the compounds cannot be classified as half-metallic ferromagnets.

X-ray magnetic circular dichroism of pulsed laser deposited Co2MnSn and Co2MnSb thin films grown on GaAs (001)

“…Figure 3 shows a similar display of spectra for the Mn L 2,3 edge. 23 The total magnetic moment per formula unit from this calculation is 5.32 B , which is higher than the obtained bulk value of 4.94 B . It is natural to expect a slightly higher value compared to the bulk because we have not accounted for the contribution from Sn which is likely antiferromagnetically aligned to the Co and Mn moments, but this alone cannot account for the higher value of moment.…”

Antiferromagnetic dipolar ordering in[Co2MnGe∕V]Nmultilayers

“…For the Co 2 Mn(Si,Ge,Sn) fully spin polarized group of Heusler compounds spin polarized neutron diffraction measurements on bulk samples have been employed to determine the degree of spin polarization at the Fermi level [46]. This methods probe the spatial distribution of the magnetization, details of which depend sensitively on the spin polarization.…”

Optically induced magnetization dynamics and variation of damping parameter in epitaxialCo2MnSiHeusler alloy films

“…7͒ corresponding to a value of 1030 emu/ cm 3 for a lattice parameter of 0.565 nm. Since Co 2 MnSi has a Curie temperature of 985 K, 7 the room temperature magnetization is expected to be close to 1000 emu/ cm 3 . However, recent SQUID magnetometry measurements made upon epitaxial films yielded a reduced magnetization, 5 its value falling from 850 to 800 emu/ cm 3 as T an was increased from 350 to 500°C.…”