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Strain-induced high ferromagnetic transition temperature of MnAs epilayer grown on GaAs (110).

Xu P, Lu J, Chen L, Yan S, Meng H, Pan G, Zhao J - Nanoscale Res Lett (2011)

Bottom Line: Specular and grazing incidence X-ray diffractions are used to study the influence of different strain states of MnAs/GaAs (110) and MnAs/GaAs (001) on the first-order magnetostructural phase transition.It comes out that the first-order magnetostructural phase transition temperature Tt, at which the remnant magnetization becomes zero, is strongly affected by the strain constraint from different oriented GaAs substrates.Our results show an elevated Tt of 350 K for MnAs films grown on GaAs (110) surface, which is attributed to the effect of strain constraint from different directions.PACS: 68.35.Rh, 61.50.Ks, 81.15.Hi, 07.85.Qe.

View Article: PubMed Central - HTML - PubMed

Affiliation: State Key Laboratory for Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P,O, Box 912, Beijing 100083, China. jhzhao@red.semi.ac.cn.

ABSTRACT
MnAs films are grown on GaAs surfaces by molecular beam epitaxy. Specular and grazing incidence X-ray diffractions are used to study the influence of different strain states of MnAs/GaAs (110) and MnAs/GaAs (001) on the first-order magnetostructural phase transition. It comes out that the first-order magnetostructural phase transition temperature Tt, at which the remnant magnetization becomes zero, is strongly affected by the strain constraint from different oriented GaAs substrates. Our results show an elevated Tt of 350 K for MnAs films grown on GaAs (110) surface, which is attributed to the effect of strain constraint from different directions.PACS: 68.35.Rh, 61.50.Ks, 81.15.Hi, 07.85.Qe.

No MeSH data available.


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XRD patterns. XRD patterns measured by synchrotron radiation for reflections of MnAs  in the specular geometry,  and (0002) in the grazing incidence geometry for samples A (black), B (blue), C (wine), and D (red). The radial scan along MnAs (0002) of sample C can be fitted well by two peaks centered at 31.44 and 31.61 which can be ascribed to MnAs (0002) and GaAs (002), respectively (d).
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Figure 5: XRD patterns. XRD patterns measured by synchrotron radiation for reflections of MnAs in the specular geometry, and (0002) in the grazing incidence geometry for samples A (black), B (blue), C (wine), and D (red). The radial scan along MnAs (0002) of sample C can be fitted well by two peaks centered at 31.44 and 31.61 which can be ascribed to MnAs (0002) and GaAs (002), respectively (d).

Mentions: In order to probe the effect of anisotropic strain on the first-order magnetostructural phase transition, we performed synchrotron XRD measurements. The experimental results are shown in Figure 5. The orthorhombic notation is used for the α-phase lattice parameters, in which aortho, bortho, and cortho stand for the spacing between MnAs (0001), MnAs , and MnAs , respectively. The lattice parameters, primitive cell volume, and transition temperature are shown in Table 2. Early in the 1960s, Bean and Rodbell and Menyuk et al. concluded that Tt is proportional to the primitive cell volume and a larger primitive cell volume (V) corresponds to a higher Tt based on the magnetostrictive model [15,16]. Clearly our experimental results cannot be explained by a simple effect of primitive cell volume variation, and Tt is not a linear function of V. For example, as to all the epitaxial films studied here, the primitive cell volume is smaller than that of the bulk material, while ferromagnetic hexagonal α-phase can coexist with paramagnetic orthorhombic β-phase to a higher temperature. Furthermore, there is remarkable difference between lattice parameters for MnAs films grown on GaAs (001) and GaAs (110). For sample A, grown on GaAs (001), aortho is larger, while bortho and cortho are smaller than that for sample D, grown on GaAs (110). In good agreement with the experimental and theoretical results of Iikawa et al. [23], all these changes result in a lower transition temperature (stretching of the lattice parameters in the basal plane results in a higher Tt, while stretching of lattice parameters along the perpendicular direction lowers Tt).


Strain-induced high ferromagnetic transition temperature of MnAs epilayer grown on GaAs (110).

Xu P, Lu J, Chen L, Yan S, Meng H, Pan G, Zhao J - Nanoscale Res Lett (2011)

XRD patterns. XRD patterns measured by synchrotron radiation for reflections of MnAs  in the specular geometry,  and (0002) in the grazing incidence geometry for samples A (black), B (blue), C (wine), and D (red). The radial scan along MnAs (0002) of sample C can be fitted well by two peaks centered at 31.44 and 31.61 which can be ascribed to MnAs (0002) and GaAs (002), respectively (d).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211171&req=5

Figure 5: XRD patterns. XRD patterns measured by synchrotron radiation for reflections of MnAs in the specular geometry, and (0002) in the grazing incidence geometry for samples A (black), B (blue), C (wine), and D (red). The radial scan along MnAs (0002) of sample C can be fitted well by two peaks centered at 31.44 and 31.61 which can be ascribed to MnAs (0002) and GaAs (002), respectively (d).
Mentions: In order to probe the effect of anisotropic strain on the first-order magnetostructural phase transition, we performed synchrotron XRD measurements. The experimental results are shown in Figure 5. The orthorhombic notation is used for the α-phase lattice parameters, in which aortho, bortho, and cortho stand for the spacing between MnAs (0001), MnAs , and MnAs , respectively. The lattice parameters, primitive cell volume, and transition temperature are shown in Table 2. Early in the 1960s, Bean and Rodbell and Menyuk et al. concluded that Tt is proportional to the primitive cell volume and a larger primitive cell volume (V) corresponds to a higher Tt based on the magnetostrictive model [15,16]. Clearly our experimental results cannot be explained by a simple effect of primitive cell volume variation, and Tt is not a linear function of V. For example, as to all the epitaxial films studied here, the primitive cell volume is smaller than that of the bulk material, while ferromagnetic hexagonal α-phase can coexist with paramagnetic orthorhombic β-phase to a higher temperature. Furthermore, there is remarkable difference between lattice parameters for MnAs films grown on GaAs (001) and GaAs (110). For sample A, grown on GaAs (001), aortho is larger, while bortho and cortho are smaller than that for sample D, grown on GaAs (110). In good agreement with the experimental and theoretical results of Iikawa et al. [23], all these changes result in a lower transition temperature (stretching of the lattice parameters in the basal plane results in a higher Tt, while stretching of lattice parameters along the perpendicular direction lowers Tt).

Bottom Line: Specular and grazing incidence X-ray diffractions are used to study the influence of different strain states of MnAs/GaAs (110) and MnAs/GaAs (001) on the first-order magnetostructural phase transition.It comes out that the first-order magnetostructural phase transition temperature Tt, at which the remnant magnetization becomes zero, is strongly affected by the strain constraint from different oriented GaAs substrates.Our results show an elevated Tt of 350 K for MnAs films grown on GaAs (110) surface, which is attributed to the effect of strain constraint from different directions.PACS: 68.35.Rh, 61.50.Ks, 81.15.Hi, 07.85.Qe.

View Article: PubMed Central - HTML - PubMed

Affiliation: State Key Laboratory for Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P,O, Box 912, Beijing 100083, China. jhzhao@red.semi.ac.cn.

ABSTRACT
MnAs films are grown on GaAs surfaces by molecular beam epitaxy. Specular and grazing incidence X-ray diffractions are used to study the influence of different strain states of MnAs/GaAs (110) and MnAs/GaAs (001) on the first-order magnetostructural phase transition. It comes out that the first-order magnetostructural phase transition temperature Tt, at which the remnant magnetization becomes zero, is strongly affected by the strain constraint from different oriented GaAs substrates. Our results show an elevated Tt of 350 K for MnAs films grown on GaAs (110) surface, which is attributed to the effect of strain constraint from different directions.PACS: 68.35.Rh, 61.50.Ks, 81.15.Hi, 07.85.Qe.

No MeSH data available.


Related in: MedlinePlus