Spin-polarized tunneling in a half-metallic ferromagnet

Abstract

Direct measurement of the conduction electron spin polarization ͑P͒ in epitaxial NiMnSb was performed to test the prediction of half metallicity in this material. Spin-polarized tunneling in NiMnSb/Al 2 O 3 /Al junctions showed P of 28%, contrary to the predicted value of 100%. Magnetoresistance measurements in NiMnSb/Al 2 O 3 /Ni 80 Fe 20 junctions concurred with this result. The discrepancy between theory and experiment is discussed. Also, the latter junctions show four nonvolatile remanent states due to the NiMnSb magnetocrystalline anisotropy, which has potential as four-level logic elements.

Structural and magnetic properties of the (001) and (111) surfaces of the half-metal NiMnSb

“…These polarisation values are consistent with a small perpendicular magnetoresistance measured for NiMnSb in a spin-valve structure [23], and a superconducting and a magnetoresistive tunnel junction [5]. Ristoiu et al showed that during the growth of the NiMnSb thin films, first Sb and then Mn atoms segregate to the surface, which is far from being perfect, thus decreasing the obtained spin-polarization [24].…”

Thin films of the Heusler alloys Cu2MnAl and Co2MnSi: recovery of ferromagnetism via solid-state crystallization from the x-ray amorphous state

“…ferromagnets with full spin polarization at the Fermi levelare promising materials for applications in spintronics [11,12]. They can be employed as spin filters [13], in spin injection/detection devices [14,15] or in magnetic tunnelling junctions (MTJs) [16]. Apart from a few oxidic compounds and Mn-doped semiconductors [17][18][19], the class of Heusler alloys provides the only metallic alloy system with halfmetallicity.…”

Surface properties of the half-and full-Heusler alloys

“…One of the most interesting problems of this new field is the spin-injection from a ferromagnet into a semiconductor, that would lead to the creation of efficient spin-filters [3], tunnel junctions [4], GMR devices for spin injection [5], etc. This has intensified the interest in the so-called half-ferromagnetic materials which have a band gap at the Fermi level (E F ) for one spin direction and thus exhibit 100% spin polarisation at E F .…”