Abstract
Knowledge of the spin-dependent electronic structure at surfaces and interfaces plays an increasingly important role when assessing possible use of novel magnetic materials for spintronic applications. It is shown that spin- and angle-resolved photoelectron spectroscopy together with ab initio electronic structure methods provides a full characterization of the surface electronic structure of ferromagnetic MnSb(0 0 0 1). Two different surface reconstructions have been compared in spin- and angle-resolved valence-band photoemission. For annealing at elevated temperatures, the (1 × 1)-structure transforms into 2 × 2 and a majority-spin peak appears at −1.7 eV inside a majority-spin bulk band gap at the surface Brillouin zone centre. Its sensitivity to oxygen supports an interpretation as magnetic compound surface state. Local spin density calculations predict at the same energy (−1.75 eV) a prominent d surface state of majority spin for (1 × 1)-Mn terminated MnSb(0 0 0 1) but no such feature for (1 × 1)-Sb termination. The calculation shows that neither the bulk nor the surface is half-metallic, in agreement with the expectation for the hexagonal NiAs structure.
Highlights
DEUTSCHE PHYSIKALISCHE GESELLSCHAFT spin for (1 × 1)-Mn terminated MnSb(0 0 0 1) but no such feature for (1 × 1)-Sb termination
Our results indicate the formation of a magnetic surface state of an intermetallic compound
The (0 0 0 1)-projection of the bulk band structure shows that for minority spin (figure 4(a)), there is no gap at, whereas for majority spin (figure 4(b)), a large gap opens from −0.75 to −1.75 eV. (Apparent gaps of smaller size, e.g., around the Fermi energy, are not considered because they are an effect of the finite layer thickness.) In this gap, a majority-spin surface state, non-degenerate with the bulk, is predicted for the Mn-terminated surface
Summary
The MnSb(0 0 0 1) films in the μm thickness range have been grown onto GaAs(1 1 1) by molecular beam epitaxy using growth parameters like the ones given in [11]. The peak labelled SS at −1.7 eV appears inside but close to the border of this gap This border is, defined by 6+, which is far away in k-space, so that the expected majority-spin emission is the one marked in figure 3(a) at −3.0 eV. From this argument it becomes obvious that the peak SS cannot be explained from the band structure of stoichiometric bulk MnSb leaving a non-stoichiometric bulk state and a surface state of the compound as possible interpretations. The bulk-derived minority-spin peak at −2.0 eV (A↓3 , bonding) appears to be reduced in intensity as well. A similar observation is made for the majority-spin spectrum
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