Ab initio calculations and synthesis of the off-stoichiometric half-Heusler phase Ni 1 − x Mn 1 + x Sb

• Published in: Journal of applied physics 2010-11, Vol.108 (9), p.093712-093712-9
• Main Authors: Ekholm, M., Larsson, P., Alling, B., Helmersson, U., Abrikosov, I. A.
• Format: Article
• Language: English
• Subjects: TECHNOLOGY; TEKNIKVETENSKAP
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.3476282

We perform a combined theoretical and experimental study of the phase stability and magnetism of the off-stoichiometric Ni 1 − x Mn 1 + x Sb in the half-Heusler crystal phase. Our work is motivated by the need for strategies to engineer the magnetism of potentially half-metallic materials, such as NiMnSb, for improved performance at elevated temperatures. By means of ab initio calculations we investigate Ni 1 − x Mn 1 + x Sb over the whole composition range 0 ≤ x ≤ 1 of Ni replacing Mn and show that at relevant temperatures, the half-Heusler phase should be thermodynamically stable up to at least x = 0.20 with respect to the competing C38 structure of Mn 2 Sb . Furthermore we find that half-Heusler Ni 1 − x Mn 1 + x Sb retains half-metallic band structure over the whole concentration range and that the magnetic moments of substitutional Mn Ni atoms display magnetic exchange interactions an order of magnitude larger than the Ni-Mn interaction in NiMnSb. We also demonstrate experimentally that the alloys indeed can be created by synthesizing off-stoichiometric Ni 1 − x Mn 1 + x Sb films on MgO substrates by means of magnetron sputtering.