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Magnetic and transport properties of SiMn films with the high Mn content

Magnetic and transport properties of SiMn films with the high Mn content. PRB, 84, 075209 (2011). Rylkov V.V. Tugushev V.V. Nikolaev S.N. . Perov N.S. Semisalova A. S. Caprara Podolskii V.V. Lesnikov V.P. A. Lashkul. RRC “Kurchatov Institute”, Moscow, Russia. Aronzon B.A.

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Magnetic and transport properties of SiMn films with the high Mn content

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  1. Magnetic and transport properties of SiMn films with the high Mn content PRB, 84, 075209 (2011) Rylkov V.V. Tugushev V.V. Nikolaev S.N. . Perov N.S. Semisalova A. S. Caprara Podolskii V.V. Lesnikov V.P. A. Lashkul RRC “Kurchatov Institute”, Moscow, Russia Aronzon B.A. Moscow State University, Russia Dipartamento di Fisica, Universita di Roma NIFTI, N. Novgorod , Russia Lappeenranta University of Technology, Finland

  2. Outline 1 Introduction. What is known about SiMn structures? 2 Transport, AHE 3 Magnetic properties 4 Model 5 Conclusion

  3. MnxSi1-x Si Si Mn Mn The equilibrium solubility of Mn in Si is very low(~1016cm-3). It is needed to reach higher manganese concentration (1021cm-3). Mn impurities in Si favor interstitial position and act as donors, that results in very weak exchange interaction. While strong hybridization of Mn 3d states with s,p states in Si occurs if Mn enter substitutional (MnSi) positions as acceptors Binary compounds of 3d metals with Si are weak itinerant magnets of helicoidal type with Curie temperature <50K (no hysteresis loop).

  4. What is known about magnetic properties of MnxSi1-x 1. Ion beam implantation Mn(х≈ 0.8 %) :Tc > 400 K (M. Bolduc et al., Phys. Rev. B 71, 033302 (2005)). Magnetism is due to paramagnetic defects T. Dubroca et al., Appl. Phys. Lett. 88, 182504 (2006); A.F. Orlov, A.B. Granovsky et al.JETP 109, 602 (2009) 2. Magnetron sputtering. (х~ 5%):ТС ≈ 250К (X.C. Liu, Z.H. Lu et al.,J. Appl. Phys. 100, 073903 (2006); 102, 033902 (2007)), p≈1016cm-3 3. MBE [Si(20Å)/Mn(1 - 2Å)](х~5-10%):ТС≈ 300К (S.H. Chiu et al.,J. Appl. Phys. 103, 07D110 (2008)).While (х<17,5%):ТС ≈ 3К (L. Zeng, PRB, 77, 073306 (2008)) Magnetiztion; no AHE. 4. Magnetron co-sputtering. Mn-doped amorphous Si:H (х~10 %):Т ≈ 150К (J.H. Yao, S.C. Li et al., Appl. Phys. Lett. 94, 072507 (2009)). 5. Mn –Si complexes (2-3)B/Mn (Q. Liu et al. Phys. Rev. B 77, 245211 (2008)) and self- organized in Si1-xMnx molecular clusters (S. Zhou et al. PRB 75, 085203 (2007); 80, 174423 (2009)) (> 0.2 B/Mn) Mn4Si7 ТС ≈ 50К (A. Sulpice et al.,JMMM. 272-276, 519 (2004)).

  5. Method: Anomalous Hall Effect The Hall resistance RHd= yx = R0B + RsM R0 and Rs are the ordinary and anomalous Hall coefficients. Anomalous Hall Effect is proportional to magnetization. Two types of mechanisms: skew –scattering - Rs Rxxand side-jump - Rs R2xx For both mechanisms AHE depends on the strength of the spin-orbit interaction and spin polarization of carriers.The sign of either of the two contributions canbe positive or negative depending on an interplay between the orientationsof orbital and spin momenta as well as on the character (repulsive vs.attractive) of scattering potentials. [T. Dietl (2007)] AHE current arises because the impurity cross-section seen by beam of electrons possesses right-left asymmetry T.Jungwirth et al.(2006), T. Dietl et al.(2003), S.Y. Liuet al. (2005), V.K. Dugaevet al. (2005) v(k) = grad [ε(k)]/h + (e/h)E(k) z(k) = 2Im[<u/ky|u/kx>]  - does not depend on scattering

  6. Why Anomalous Hall Effect ? • AHE depends on the strength of the spin-orbit interaction and spin polarization of carriers • AHE is not affected by the magnetism of substrate • AHE mainly is not affected by the inclusion of second phase • AHE is not need an expensive equipment and could be measured easily

  7. Parameters ofMnxSi1-x samples, x ≈ 0.35 Hole concentration p ≈ (2 – 3)1022cm-3

  8. Microanalysis Report EDAX ZAF Quantification Standardless SEC Table : Default

  9. Anomalous Hall effect up to room temperature Hall resistance The Hall resistance is determined mainly by the anomalous component even at room temperature and has negative sign while normal Hall effect is positive. Hysteresis is observed up to 230 К. Hole concentration obtained from the normal Hall effect p 21022cm-3. Rs 2.410-8Ohmcm/Gs(10-7 Ohmcm/Gsfor GaMnAs with p  1021cm-3, S.H. Chun, et al., Phys. Rev. Lett. 98, 026601 (2007) ).

  10. Comparison with Mn4Si7 U. Gottlieb at el., JMMM (2004) and Our results

  11. Comparison with (Si:H)Mn Our results J.H. Yao et al., Appl. Phys.Lett. 94, 072507 (2009) JETP Letters 89, 707, (2009) Comparison with Mn4Si7 MnxSi1-x TC> 300K Mn4Si7 Tc<50K U. Gottlieb at el., JMMM (2004)

  12. Halleffect For sample grown at Tg =300 C coercive field Bcstrongly rises (2.8 times) when temperature lowering from 56 K down to 5 K. It is so also for Ga1-x MnxAs (atТ ТС). Contrary to that for sample grown at Tg =350 C coercive field Bcdiminisheswith temperature lowering from 59 K down to 5 K.

  13. Magnetization B, T Magnetic moment perMnatom0.1 B/Mn. InMn4Si70.012B/Mn.

  14. Correlation between AHE and magnetization Si1-хMnх/Al2O3 (№2) d=57 nm

  15. Coercitivity and saturation magnetization vs. temperature measured by AHE and SQUID

  16. Curie temperature. Magnetization. Temperature dependence Coupling betweenlocal magnetic moments of MnDdefects in the MnnSimhostmediated by spin fluctuations (SF). For DMS M(T) could be fitted by F(y) = 1 − yn, with y = T/TC(n ≈ 2 for GaMnAs) In the SF mode y = T (T − ThC)/Tc(TC− ThC) ThC = 50 K – Curie temperatureof matrix (host). n = 1.3–1.5

  17. Model Si1-xMnX MnSiy Mn4Si7MnSi1.75 35%MnMnSi1.86 Magnetic defects, molecular cluster with magnetic moment (2-3)B/Mn Q. Liu et al. [Phys. Rev. B 77, 245211 (2008)] HOST Weak itinerant magnet of helicoidal type Spin density is delocolized due to hybridization of Mn 3d – states and Si (s,p) - states Magnetic moment ~ 0.1B/Mn Mn atoms in molecular clusters ~ (3-5) %.Distance between them a0 ~ 10-12 Å.In the molecular cluster 4-5Si atoms per Mn. Tetrahedral arrangementof Sisurrounding Mn.

  18. Modelfor long-range order FM Two contributions RKKY (through free carriers21022cm-3) The long-range ferromagnetic order at high temperatures is mainly due to the Stoner enhancement of the exchange coupling between magnetic defects through thermal spin fluctuations (“paramagnons”) in the matrix. Tugushev et al. Physica B (2006); Nikolaev et al. JETP letters (2009) (Rij) – local susceptibility. SF(Rij)≈RKKY(ξSFkF)2≈N(EF)(ξSFkF)2 - ξSF – correlation length is about 1.5 nm, (kF)-1– 0.5 nm.

  19. Results forMnxSi1-x/Al2O3 The Hall resistance in MnxSi1-xis determined mainly by the anomalous component. Hysteresis is observed up to 230 К. Magnetic moment is about 0.1BperMn, that is ten times higher than in Mn4Si7 0.01B/Mn. At temperatures below 50 K resistivity decreases drastically. Properties of our structures differ from Mn4Si7 . Tc is about 300 K.

  20. Comparison betweenMnxSi1-x on Al2O3andGaAs

  21. Comparison betweenMnxSi1-x on Al2O3andGaAs

  22. Comparison betweenMnxSi1-x/Al2O3and MnxSi1-x/GaAs samples For MnxSi1-x/GaAs Hall resistance ρxyis remarkably higher then inMnxSi1-x/Al2O3 AHE in MnxSi1-x/GaAs is clearly observed at 300K and its amplitude weakly depends on temperature between 5 K and 190 K, while slope diminishes. The Hall angle tangent  = xy/ xxis ~ 10-2 (at 200 К), that corresponds to 20 Т for normal Hall effect if mobility 5 cm2/Vs.

  23. Comparison betweenMnxSi1-x on Al2O3andGaAs At saturation the magnetic moment per Mn atom is for MnSi/Al2O3 ≈0.07 μB/Mn (200 K) ≈0.03 μB/Mn (300 K) MnSi/GaAs ≈0.3μB/Mn (200 K) ≈0.08μB/Mn (300 K)

  24. Parameters ofMnxSi1-x samples, x ≈ 0.35 Hole concentration p ≈ (2 – 3)1022cm-3

  25. Conclusion AHE is observed at room temperature being the main contribution to the Hall resistance. Hysteresis is observed up to  230 К. Tc reaches more then 300 K. Curie temperature and saturation magnetization is much higher than in Mn4Si7 and in previously studied Si based structures. Properties of these films depend on substrate We explain experimental results within the model of exchange through the spin fluctuations PRB, 84, 075209 (2011) Thank you for attention

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