Manganese surface segregation in NiMnSb

Ristoiu, D.; Nozières, J. P.; Borca, Camelia N.; Borca, Bogdan; Dowben, Peter A.

doi:10.1063/1.126342

Cited by 90 publications

(88 citation statements)

References 16 publications

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“…In NiMnSb, for example, extensive Mn surface segregation has been observed. 21 In another paper, this same group established a strong sensitivity of spin-polarized inverse photoemission measurements to the surface preparation of FIG. 6.…”

Section: Spin Polarizationmentioning

confidence: 99%

Magnetic, structural, and transport properties of the Heusler alloysCo2MnSiand NiMnSb

et al. 2003

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We report on structural, magnetic, transport, and spin-polarization measurements of the Heusler alloys Co 2 MnSi and NiMnSb. Laue diffraction patterns confirm the single-crystal nature of Co 2 MnSi. Roomtemperature transport measurements show a negative magnetoresistance in NiMnSb. Point-contact Andreev reflection measurements of the spin polarization yield polarization values for Co 2 MnSi and NiMnSb of 56% and 45%, respectively. Temperature dependence of resistivity for Co 2 MnSi reveals a relatively large residual resistivity ratio ( 293 K / 5 K ) typical of single-crystal Heusler alloys. In NiMnSb, resistivity and magnetization as a function of temperature show evidence of a magnetic phase transition near 90 K.

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Section: Spin Polarizationmentioning

confidence: 99%

Magnetic, structural, and transport properties of the Heusler alloysCo2MnSiand NiMnSb

et al. 2003

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“…Values of 58% and 50% for the spin-polarization at the Fermi level were obtained by Soulen et al 54 and by Mancoff et al, 55 respectively, and recently Zhu et al 56 found a value of 40% using spin-resolved photoemission measurements on polycrystalline films. Ristoiu et al 57,58,59,60 showed that during the growth of the NiMnSb thin films, Sb atoms segregate to the surface decreasing the obtained spinpolarization; they measured a value of ∼30% at 200K, while at room temperature the net polarization was practically zero. But when they removed the excess of Sb by a flash annealing, they managed to get a nearly stoichiometric ordered alloy surface terminating in MnSb.…”

Section: Introductionmentioning

confidence: 99%

Ab initio electronic and magnetic properties of half-metallic NiCrSi and NiMnSi Heusler alloys: The role of defects and interfaces

Galanakis

Özdoğan

Şaşıoğlu

2008

Journal of Applied Physics

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Using state-of-the-art first-principles calculations we study the properties of the ferromagnetic Heusler compounds NiYSi where Y stands for V, Cr or Mn. NiCrSi and NiMnSi contrary to NiVSi are half-metallic at their equilibrium lattice constant exhibiting integer values of the total spin magnetic moment and thus we concentrate on these two alloys. The minority-spin gap has the same characteristics as for the well-known NiMnSb alloy being around ∼1 eV. Upon tetragonalization the gap is present in the density of states even for expansion or contraction of the out-of-plane lattice parameter by 5%. The Cr-Cr and Mn-Mn interactions make ferromagnetism extremely stable and the Curie temperature exceeds 1000 K for NiMnSi. Surface and interfaces with GaP, ZnS and Si semiconductors are not half-metallic but in the case of NiCrSi the Ni-based contacts present spinpolarization at the Fermi level over 90%. Finally, we show that there are two cases of defects and atomic-swaps. The first-ones which involve the Cr(Mn) and Si atoms induce states at the edges of the gap which persists for a moderate-concentration of defects. Defects involving Ni atoms induce states localized within the gap completely destroying the half-metallicity. Based on single-impurity calculations we associate these states to the symmetry of the crystal.

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“…2,4 Indeed, as shown in Ref. 4, manganese segregation occurs at the NiMnSb͑100͒ surface. 4 In addition, there are several other phenomena that may contribute to the lowering of the surface Debye temperature with respect to the bulk.…”

Section: Figmentioning

confidence: 99%

“…Unfortunately, the polarization of NiMnSb is very sensitive to composition and defects 2,3 and the NiMnSb͑100͒ surface is observed to be very fragile. 2,4 The thermal motions of the surface atoms dictates many of the physical and chemical properties of a surface, such as surface diffusion, 5 anharmonicity leading to roughening transitions, 6 surface reconstructions, 7 and influence the extent of composition inhomogenities, including defects. The key descriptive parameter of the dynamic motions of atoms on the surface, as well as in the bulk, is the Debye temperature.…”

mentioning

confidence: 99%