A review of recent advances in spintronics is presented. We report the structural, magnetic, electrical and thermal properties of the ferromagnetic half-Heusler alloy NiMnSb grown by arcmelting. The bulk material is used to deposit highly crystalline thin films at low temperature (200°C) by Pulsed Laser Deposition (PLD). The structural and magnetic and transport properties of these films are nearly bulk-like suggesting that these films can be grown by PLD in multilayer structures for efficient spin injection in spintronics.

Highly spin polarized Heusler alloys, NiMnSb and Co2MnSi, attract a great deal of interest as potential spin injectors for spintronic applications. Spintronic devices require control of interfacial properties at the ferromagnet: semiconductor contact. To address this issue we report a systematic study of the ordinary and anomalous Hall effect, in Ni 1.15Mn0.85Sb films on silicon, as a function of film thickness. In contrast to the bulk stoichiometric material, the Hall carriers in these films become increasingly electron-like as the film thickness decreases, and as the temperature increases from 50 K toward room temperature. High field Hall measurements confirm that this is representative of the majority transport carriers. This suggests that current injected from a NiMnSb: semiconductor interface may not necessarily carry the bulk spin polarization. The films also show a low temperature upturn in the resistivity, which is linked to a discontinuity in the anomalous Hall coefficient. Overall these trends indicate that the application of Heusler alloys as spin injectors will require strictly controlled interfacial engineering, which is likely to be demanding in these ternary alloys.

NiMnSb has attracted a great deal of interest as a spin injector/detector in spintronic devices because it has a Curie temperature of 728 K and is predicted to be half-metallic (100% spin polarized). NiMnSb has been reported to have greatly reduced surface polarization, and to lose its half metallicity above 80 K. Here we report the investigation of the surface polarisation and electronic structure of NiMnSb by measurement of the transport spin polarization using point contact Andreev reflection spectroscopy, and anomalous Hall effect in thin films on Si(00 1). A comparison to bulk properties is made. © 2003 Elsevier B.V. All rights reserved.

The transport properties of pulsed-laser-deposited NiMnSb films on silicon as a function of film thickness were discussed. It was found that a low-temperature upturn was observed in the resistivity for film thicknesses of 130 nm and below. It was observed that as the film thickness decreased, the magnitude of both the resistivity upturn and the magnetoresistance increased. Analysis shows that the evolution of the field dependence of the magnetoresistance appeared similar to the silver chalcogenides and was indicative of a crossover from hole-dominated to electron-dominated transport as the temperature increased.

We have grown films of the half-metallic ferromagnet NiMnSb on single crystals of the narrow gap semiconductor InSb by pulsed laser deposition. NiMnSb is a possible candidate for spin injection applications. The film depositions occurred at 200°C. X-ray diffraction studies indicate a high degree of (220) texture and no secondary phases. A saturation magnetization of four Bohr magnetons, μB. at 5 K and coercive fields down to 5 Oe at 300 K indicate the good quality of the films.

We report the growth of single-phase, stoichiometric polycrystalline thin films of the half-Heusler ferromagnet NiMnSb, predicted to be half-metallic, on single crystal InSb (100) substrates heated at 200°C by pulsed laser deposition. The films exhibit saturation magnetization of 4 μB/ formula unit at 5 K and coercive fields of 2 Oe at 300 K indicative of their good structural quality. At low temperatures (7<200 K) the system behaves like a Heisenberg ferromagnet as expected for a half-metal, while at T>200 K it behaves like an itinerant ferromagnet. The resistivity of the film at 5 K is 6 μΩ cm. © 2004 American Institute of Physics.

The synthesis and physical properties of arc melted NiMnSb were studied using X-ray diffraction analysis. It was observed that the half metallicity in NiMnSb is supported by the integer saturation magnetization value at 5 K. It was found that the magnetic properties were due to magnetic moments localized at the Mn atoms. The results show that in the temperature region of 80 K to 150 K a crossover takes place from half metallic behavior to normal ferromagnetic behavior.