Lithuanian Journal of Physics article / Lietuvos fizikos žurnalo straipsnis

ALTERNATING CURRENT SUSCEPTIBILITY AND MAGNETISATION OF NANOCRYSTALLINE Co₂MnSi HEUSLER ALLOY FILMS
Bonifacas Vengalis^a, Andrius Maneikis^a, Gražina Grigaliūnaitė-Vonsevičienė^b, Remigijus Juškėnas^a, and Algirdas Selskis^a
^aCenter for Physical Sciences and Technology, Goštauto 11, 01108 Vilnius, Lithuania
^bVilnius Gediminas Technical University, Saulėtekio 11, 10223 Vilnius, Lithuania
Email: veng@pfi.lt

Received 11 June 2019; revised 16 September 2019; accepted 10 November 2019

The Co₂MnSi (CMS) Heusler alloy films with thickness d = 90 ÷ 110 nm were grown by DC magnetron sputtering on both nonheated and heated Si(100) and MgO(100) substrates. The films grown (annealed) at T ≥ 400°C demonstrated a nanocrystalline structure with a partially ordered B2 phase and traces of a highly ordered L2₁ phase as found from XRD measurements. The films deposited onto the nonheated substrates followed by annealing at T_ann = 300 ÷ 500°C demonstrated a gradual increase of the saturation magnetisation, M_sat, up to about 4.0 μB/f.u. (at 295 K) while the coercity field, H_c, of the films increased from about 10 to 12 kA/m with T_ann increasing from 400 to 500°C. Unusually low H_c values of about 0.1 and 0.3 kA/m have been indicated for the films grown in situ at 400°C on MgO and Si, respectively. A significant increase of the H_c values found for the films grown in situ at T_s = 450°C and reduced M_sat values for similar films grown at 500°C have been associated with the instability of the ordered L2₁ structure at high temperatures.

Keywords: Co₂MnSi, Heusler alloy films, AC magnetic susceptibility, magnetisation, magnetoresistance
PACS: 75.60.-d, 72.15 Gd, 75.70.-i, 75.30.-m

NANOKRISTALINIŲ Co₂MnSi HEUSLERIO LYDINIO SLUOKSNIŲ MAGNETINIS JAUTRIS IR ĮMAGNETĖJIMAS
Bonifacas Vengalis^a, Andrius Maneikis^a, Gražina Grigaliūnaitė-Vonsevičienė^b, Remigijus Juškėnas^a, Algirdas Selskis^a

^aFizinių ir technologijos mokslų centras, Vilnius, Lietuva
^bVilniaus Gedimino technikos universitetas, Vilnius, Lietuva

Plonieji Co₂MnSi (CMS) sluoksniai (d = 90 ÷ 10 nm) buvo gaminami pastoviosios srovės magnetroninio dulkinimo būdu ant kaitinamų (T_s = 200 ÷ 500°C) ir nekaitinamų Si(100) ir MgO(100) padėklų. Sluoksniai, užauginti ant nekaitinamų padėklų, buvo papildomai kaitinami vakuume. Elektroninės mikroskopijos ir rentgeno difrakcijos tyrimai parodė, kad nanokristaliniai CMS sluoksniai su iš dalies susitvarkiusiomis B2 ir L2₁ kristalinėmis struktūromis susidaro esant aukštesnėms auginimo (kaitinimo) temperatūroms (T_s, T_ann, ≥400 °C). Sluoksnių, užaugintų ant nekaitintų padėklų, magnetinio įspūdingumo tyrimai atskleidė, kad kaitinimo temperatūrai didėjant nuo 400 °C iki 500 °C jų koercinio lauko H_c vertės kambario temperatūroje kinta nežymiai (10 ÷ 12 kA/m), o soties įmagnetėjimo Msat vertės padidėja iki 4,0 μB/f.u. Sluoksniai, kurie buvo auginami ant kaitinamų MgO ir Si padėklų esant 400 °C temperatūrai, pasižymėjo ypač mažomis H_c vertėmis (atitinkamai ≅ 0,1 ir 0,3 kA/m). Siekiant paaiškinti nepalyginamai didesnes sluoksnių H_c vertes auginant 450 °C temperatūroje ir pastebimą M_sat verčių sumažėjimą auginant sluoksnius dar aukštesnėje (500 °C) temperatūroje padaryta prielaida, kad tvarkioji L2₁ fazė nėra patvari aukštoje (≥450 °C) temperatūroje.

References / Nuorodos

[1] C. Felser, L. Wollmann, S. Chadov, G.H. Fecher, and S.S.P. Parkin, Basics and prospective of magnetic Heusler compounds, APL Mater. 3, 041518-1–8 (2015),
https://doi.org/10.1063/1.4917387
[2] T. Graf, C. Felser, and S.S.P. Parkin, Simple rules for the understanding of Heusler compounds, Prog. Solid State Chem. 39, 1–50 (2011),
https://doi.org/10.1016/j.progsolidstchem.2011.02.001
[3] A. Akriche, H. Bouafia, S. Hiadsi, B. Abidri, B. Sahli, M. Elchikh, M.A. Timaoui, and B. Djebour, First-principles study of mechanical, exchange interactions and the robustness in Co₂MnSi full Heusler compounds, J. Magn. Magn. Mater. 422, 13–19 (2017),
https://doi.org/10.1016/j.jmmm.2016.08.059
[4] C.J. Palmstrøm, Heusler compounds and spintronics, Prog. Cryst. Growth Character. Mater. 62, 371–397 (2016),
https://doi.org/10.1016/j.pcrysgrow.2016.04.020
[5] F. Yang, W. Li, J. Li, H. Chen, D. Liu, X. Chen, and C. Yang, The microstructure and magnetic properties of Co₂MnSi thin films deposited on Si substrate, J. Alloys Compd. 723, 188–191 (2017),
https://doi.org/10.1016/j.jallcom.2017.06.232
[6] D. Erb, G. Nowak, K. Westerholt, and H. Zabel, Thin films of the Heusler alloys Cu₂MnAl and Co₂MnSi: recovery of ferromagnetism via solid-state crystallization from the x-ray amorphous state, J. Phys. D 43, 285001–285009 (2010),
https://doi.org/10.1088/0022-3727/43/28/285001
[7] H. Liu, M. Tang, B.L. Guo, C. Jin, P. Li, and H.L. Bai, Effect of deposition temperature on the structure, magnetic and transport properties in Co₂MnSi Heusler films, Appl. Phys. A 121, 141–148 (2015),
https://doi.org/10.1007/s00339-015-9397-4
[8] H. Pandey and R.C. Budhani, Structural ordering driven anisotropic magnetoresistance, anomalous Hall resistance and its topological overtones in full-Heusler Co₂MnSi thin films, J. Appl. Phys. 113, 203918–203927 (2013),
https://doi.org/10.1063/1.4808098
[9] K. Kim, S.J. Kwon, and T.W. Kim, Characterization of Heusler alloy thin film, Cu2MnAl and Co₂MnSi, deposited by co-sputtering method, Phys. Status Solidi B 241(7), 1557–1560 (2004),
https://doi.org/10.1002/pssb.200304580
[10] Y. Takamura, R. Nakane, and S. Sugahara, Analysis of L2₁-ordering in full-Heusler Co₂FeSi alloy thin films formed by rapid thermal annealing, J. Appl. Phys. 105, 07B109-1–3 (2009),
https://doi.org/10.1063/1.3075989
[11] M.A.I. Nahid, M. Oogane, H. Naganuma, and Y. Ando, Study of structure, magnetic and electrical properties of Co₂MnSi Heusler alloy thin films onto n-Si substrates, IEEE Trans. Magn. 45(10), 4030–4032 (2009),
https://doi.org/10.1109/TMAG.2009.2024320
[12] M. Kawano, S. Yamada, S. Oki, K. Tanikawa, M. Miyao, and K. Hamaya, Molecular beam epitaxy growth of Co₂MnSi films on group-IV semiconductors, Japan. J. Appl. Phys. 52(4S), 884–885 (2013),
https://doi.org/10.7567/JJAP.52.04CM06
[13] O. Gaier, J. Hamrle, S.J. Hermsdorfer, H. Schultheib, and B. Hillebrands, Influence of the L2₁ ordering degree on the magnetic properties of Co₂MnSi Heusler films, J. Appl. Phys. 103, 1039101–1039105 (2008),
https://doi.org/10.1063/1.2931023
[14] M. Belmeguenai, F. Zighem, D. Faurie, H. Tuzcuoglu, S.M. Cherif, K. Westerholt, W. Seiler, and P. Moch, Structural and magnetic properties of Co₂MnSi thin films, Phys. Status Solidi A 209(7), 1328–1333 (2012),
https://doi.org/10.1002/pssa.201228039
[15] S. Kawagishi, T. Uemura, Y. Imai, K.I. Matsuda, and M. Yamamoto, Structural, magnetic, and electrical properties of Co₂MnSi/MgO/n-GaAs tunnel junctions, J. Appl. Phys. 103, 07A703 (2008),
https://doi.org/10.1063/1.2830833
[16] T. Ishikawa, S. Hakamata, K. Matsuda, T. Uemura, and M. Yamamoto, Fabrication of fully epitaxial Co₂MnSi/MgO/Co₂Mn Si magnetic tunnel junctions, J. Appl. Phys. 103, 07A919 (2008),
https://doi.org/10.1063/1.2843756
[17] H. Liu, Y. Honda, T. Taira, K. Matsuda, M. Arita, T. Uemura, and M. Yamamoto, Giant tunneling magnetoresistance in epitaxial Co₂MnSi/MgO/Co₂MnSi magnetic tunnel junctions by half-metallicity of Co₂MnSi and coherent tunneling, Appl. Phys. Lett. 101, 132418 (2012),
https://doi.org/10.1063/1.4755773
[18] S. Tsunegi, Y. Sakuraba, M. Oogane, K. Takanashi, and Y. Ando, Large tunnel magnetoresistance in magnetic tunnel junctions using a Heusler alloy electrode and a MgO barrier, Appl. Phys. Lett. 93, 112506 (2008),
https://doi.org/10.1063/1.2987516
[19] G. Ortiz, A. Garcıa-Garcıa, N. Biziere, F. Boust, J.F. Bobo, and E. Snoeck, Growth, structural, and magnetic characterization of epitaxial Co₂MnSi films deposited on MgO and Cr seed layers, J. Appl. Phys. 113, 043921 (2013),
https://doi.org/10.1063/1.4789801
[20] A. Hirohata, S. Ladak, N.P. Aley, and G.B. Hix, Si segregation in polycrystalline Co₂MnSi films with grain size control, Appl. Phys. Lett. 95, 252506 (2009),
https://doi.org/10.1063/1.3276073
[21] M.I. Youssif, A.A. Bahgat, and I.A. Ali, AC magnetic susceptibility technique for the characterization of high temperature superconductors, Egypt. J. Sol. 23(2), 231–250 (2000),

https://mafiadoc.com/ac-magnetic-susceptibility-technique-for-the-eg-mrs_5b59ee3b097c47d7288b45f6.html

[22] M. Balanda, AC susceptibility studies of phase transitions and magnetic relaxation: conventional, molecular and low-dimensional magnets, Acta. Phys. Pol. 124(6), 964–976 (2013),
https://doi.org/10.12693/APhysPolA.124.964
[23] E. Garaio, J.M. Collantes, J.A. Garcia, F. Plazaola, S. Mornet, F. Couillaud, and O. Sandre, A wide-frequency range AC magnetometer to measure the specific absorption rate in nanoparticles for magnetic hyperthermia, J Magn. Magn. Mater. 368, 432–437 (2014),
https://doi.org/10.1016/j.jmmm.2013.11.021
[24] F. Gömöry, Topical Review. Characterization of high-temperature superconductors by AC susceptibility measurements, Supercond. Sci. Technol. 10, 523–542 (1997),
https://doi.org/10.1088/0953-2048/10/8/001
[25] R. Hein, ac magnetic susceptibility, Meissner effect, and bulk superconductivity, Phys. Rev. B 33(11), 7539–7549 (1985),
https://doi.org/10.1103/PhysRevB.33.7539
[26] M. Ohashi, G. Oomi, and I. Satoh, AC magnetic susceptibility studies of single crystalline CeNiGe₂ under high pressure, J. Phys. Soc. Jpn. 76, 114712 (2007),
https://doi.org/10.1143/JPSJ.76.114712
[27] D.K. Oh, C.E. Lee, J.I. Jin, and S.J. Noh, Design of a sensitive ac magnetic susceptibility measurement system, J. Magn. 2(2), 55–57 (1997),
[PDF]
[28] Y.T. Chen, S.H. Lin, and T.S. Sheu, Effect of low-frequency AC magnetic susceptibility and magnetic properties of CoFeB/MgO/CoFeB magnetic tunnel junctions, Nanomaterials 4, 46–54 (2014),
https://doi.org/10.3390/nano4010046