Effective surface Debye temperature for NiMnSb(100) epitaxial films

Abstract

Hordequin, Ch.; Pierre, J.; and Nozie`res, J. P. , "Effective surface Debye temperature for NiMnSb.100. epitaxial films" (2000). Peter Dowben Publications. 29.

Are half-metallic ferromagnets half metals? (invited)

“…In the case of NiMnSb, nearly dispersionless transverseand logitudinal optical modes are observed at about 28 meV, 58 as illustrated by the experimental phonon band structure reproduced in Fig. 5.…”

“…59 The effect occurs where the magnon dispersion crosses the longitudinal optical branch of the phonons, at ka/2 ϭ0.3. 59,60 The lowest transverse optical modes in these systems, about 23 meV for La 0.7 A 0.3 MnO 3 (A ϭCa, Sr), 59,60 suggest metamagnetic transitions should occur in the manganese perovskites, similar to those observed in NiMnSb, 58 at about 84 K. This suggests that the loss of net spin polarization should occur, and indeed there are indications this does occur, as noted above, at about 100-130 K. 46 -50 The magnon phonon coupling is quite strong, 61,62 leading to complete damping of the magnons from about ka/2 Ϸ0.3 to the Brillouin zone boundary. [59][60][61] Similar phonon modes exist in a variety of compounds, including materials such as CrO 2 and Fe 3 O 4 .…”

The finite-temperature densities of states for half-metallic ferromagnets

“…It is already known [23] that a nearly dispersionless transverse optical mode occurs at about 28 meV in NiMnSb. In terms of 3k B T , this corresponds to 103 K -very close to the temperature at which there is a dramatic loss in Ni and Mn moments in NiMnSb [2].…”

A Landau-Ginzburg Description of Sb Overlayers

“…Antimony is a semimetal characterized by a very small negative energy gap [2]; the overlap and Fermi energies are about 180 meV and 90 meV, respectively, and the electron and hole carrier densities are of comparable magnitude (about 5 × 10 -19 cm -3 ) [2]. The preparation and characterization of the sputtered NiMnSb films considered in this work has been described elsewhere [3][4][5]. The Sb grows epitaxially on NiMnSb, with a <100> orientation, a cubic structure, a 3.1 Å lattice constant [6].…”