Half-metallic ferromagnets. II. Transport properties of NiMnSb and related inter-metallic compounds

Abstract

For pt.I see ibid., vol.1, p.2341 (1989). The electrical resistivity and the Hall effect of inter-metallic compounds XMnSb (X=Pt, Ni, Au) and PtMnSn were investigated in the temperature region 4-1000 K. The results for the anomalous Hall effect were analysed in terms of skew scattering and side-jump contributions. This analysis is possible in a half-metallic ferromagnet because the conduction electron spin polarisation at T=0 K is known.

Evidence for two-band magnetotransport in half-metallic chromium dioxide

“…7, similar to that of PtMnSb from Ref. 33. That these features have some commonality in half-metallic ferromagnets and the likely association with an energy scale ⌬ warrants further investigation.…”

“…The analysis indicates that this is due to a decrease in R h ͑and hence an increase in p and h ) rather than, say, different scattering rates. This is difficult to understand; however, it is interesting to note that a similar, inexplicable decrease in the Hall coefficient was observed for the half-metallic Heusler alloy NiMnSb for temperatures between 4 and 100 K, with constant behavior above 100 K. 33 Since b is constant above 100 K, we suspect that R h is as well. There is also a measurable decrease in R e between 10 and 50 K as shown in Fig.…”

Antiferromagnetic dipolar ordering in[Co2MnGe∕V]Nmultilayers

“…Actually for NiMnSb this type of behaviour for temperatures below 80 K has been detected. Additionally the Hall coefficient exhibits an anomalous temperature dependence in this temperature range, strongly suggesting a thermal excitation of charge carriers across a gap coexisting with metallic conductivity [41,42]. More directly, positron annihilation experiments on bulk single crystals from the NiMnSb phase were found to be consistent with 100% spin polarization at the Fermi level [43], which could additionally be confirmed by infrared absorption experiments [44].…”

“…The first attempts to prove the half-metallicity used electron transport measurement to test the existence of a gap in the spin down electron band [41,42]. Since in the half-metal for temperatures small compared to the gap in the minority spin band there is only one spin direction at the Fermi level available, it is expected that electronic scattering processes involving spin flips and longitudinal spin wave excitations are inhibited.…”

Ab initio calculations and synthesis of the off-stoichiometric half-Heusler phase Ni1−xMn1+xSb

“…2 Several experimental studies on bulk samples including measurements of resistivity, Hall effect, and magnetic properties arrived at the conclusion that the ground state of NiMnSb is half-metallic. 2,3 This was supported by the positron-annihilation measurements of bulk spin-polarization by Hanssen et al 4 In contrast, surface sensitive techniques, such as superconducting point contact measurements ͑Andreev reflection 5 ͒ 6,7 and spin-resolved photoemission spectroscopy 8,9 have failed to reproduce spin-polarization beyond the extent of a normal ferromagnet, even at low temperature. Calculations indicate NiMnSb surfaces and interfaces not to be half-metallic in general but using a suitably chosen interface-such as ͑111͒ oriented CdS or InP-halfmetallicity can be restored.…”