Ge 0.94 Mn 0.06 nanocolumn thin film is a unique phase of GeMn diluted magnetic semiconductors (DMS) which exhibit Curie temperature (TC) > 400 K. The multilayers of Ge 0.94 Mn 0.06 nanocolumns separated by nano-scaled spacers represent great interests for spintronic applications, such as spin valves or giant magneto-resistance (GMR) multilayers. In this article, we present the results obtained from the preliminary study on the exchange coupling in two types of GeMn nanocolumn/Ge multilayers. All the samples have been grown using molecular beam epitaxy (MBE). The superconducting quantum interference device (SQUID) magnetometer has been used to determine the magnetic properties of the samples. In the multilayer system Ge/[Ge 0.94 Mn 0.06 (40 nm)/Ge(d nm)]9/Ge 0.94 Mn 0.06 (40 nm)/Ge, no exchange coupling can be observed. Inversely, exchange coupling between the layers exists and depends on the thickness of the Ge spacers for the GeMn nanocolumns/Ge multilayer spin valve systems. The exchange coupling in the nanocolumns multilayer systems has been shown to be complex due to the leakage field induced by neighboring nanocolumns and the magnetic anisotropy of nanocolumns.
KeywordsMultilayersFerromagnetic SemiconductorGeMn NanocolumnsExchange CouplingThin Film
Baibich, M.N., Broto, J.M., Fert, A.F., Nguyen, V.D., Petroff, F., Etienne, P., Creuzet, G., Friederich, A. and Chazelas, J. (1988) Giant Magnetoresistance of Fe(001)/Cr(001) Magnetic Superlattices. Physical Review Letters, 61, 2472-2475. https://doi.org/10.1103/PhysRevLett.61.2472
Binasch, G., Grünberg, P., Saurenbach, F. and Zinn, W. (1989) Enhanced Magnetoresistance in Layered Magnetic Structures with Antiferromagnetic Interlayer Exchange. Physical Review B, 39, 4828. https://doi.org/10.1103/PhysRevB.39.4828
Bruno, P. (1995) Theory of Interlayer Magnetic Coupling. Physical Review B, 52, 411. https://doi.org/10.1103/PhysRevB.52.411
Slonczewski, J.C. (1989) Conductance and Exchange Coupling of Two Ferromagnets Separated by a Tunneling Barrier. Physical Review B, 39, 6995. https://doi.org/10.1103/PhysRevB.39.6995
Stiles, M.D. (2005) Ultrathin Magnetic Structures III: Fundamentals of Nanomagnetism, Volume 3 (Interlayer Exchange Coupling). Springer, Berlin.
Strijkers, G.J., Kohlhepp, J.T., Swagten, H.J.M. and de Jonge, W.J.M. (2000) Origin of Biquadratic Exchange in Fe/Si/Fe. Physical Review Letters, 84, 1812. https://doi.org/10.1103/PhysRevLett.84.1812
Mattson, J.E., Kumar, Sudha, Fullerton, Eric, E., Lee, S.R., Sowers, C.H., Grimsditch, M., Bader, S.D. and Parker, F.T. (1993) Photoinduced Antiferromagnetic Interlayer Coupling in Fe/(Fe-Si) Superlattices. Physical Review Letters, 71, 185. https://doi.org/10.1103/PhysRevLett.71.185
Yaacoub, N., Meny, C., Bengone, O. and Panissod, P. (2006) Short Period Magnetic Coupling Oscillations in Co/Si Multilayers: Theory versus Experiment. Physical Review Letters, 97, Article ID: 257206. https://doi.org/10.1103/PhysRevLett.97.257206
Kepa, H., Kutner-Pielaszek, J., Blinowski, J., Twardowski, A., Majkrzak, C.F., Story, T., Kacman, P., Galazka, R.R., Ha, K., Swagtenand, H.J.M., de Jonge, W.J.M., Yu Sipatov, A., Volobuev, V. and Giebultowicz, T.M. (2001) Antiferromagnetic Interlayer Coupling in Ferromagnetic Semiconductor Eus/PbS(001) Superlattices. EPL (Europhysics Letters), 56, 54. https://doi.org/10.1209/epl/i2001-00487-7
Gareev, R.R., Burgler, D.E., Buchmeier, M., Olligs, D., Schreiber, R. and Grunberg, P. (2001) Metallic-Type Oscillatory Interlayer Exchange Coupling across an Epitaxial FeSi Spacer. Physical Review Letters, 87, Article ID: 157202. https://doi.org/10.1103/PhysRevLett.87.157202
Dau, M.T., Le Thanh, V., Le, T.G., Spiesser, A., Petit, M., Michez, L.A. and Daineche, R. (2011) Mn Segregation in Ge/Mn5Ge3 Heterostructures: The Role of Surface Carbon Adsorption. Applied Physics Letters, 99, Article ID: 151908. https://doi.org/10.1063/1.3651488
Dau, M.T., Le Thanh, V., Le, T.G., Spiesser, A., Petit, M., Michez, L., Le, T.G., Abbes, O. and Ranguis, A. (2012) An Unusual Phenomenon of Surface Reaction Observed during Ge Overgrowth on Mn5Ge3/Ge(111) Heterostructures. New Journal of Physics, 14, Article ID: 103020. https://doi.org/10.1088/1367-2630/14/10/103020
Michez, L.A., Spiesser, A., Petit, M., Bertaina, S., Jacquot, J.F., Didier, D. and Le Thanh, V. (2015) Magnetic Reversal in Mn5Ge3 Thin Films: An Extensive Study. Journal of Physics: Condensed Matter, 27, Article ID: 266001. https://doi.org/10.1088/0953-8984/27/26/266001
Assaf, E., Portavoce, A., Hoummada, K., Bertoglio, M. and Bertaina, S. (2017) High Curie Temperature Mn5Ge3 Thin Films Produced by Non-Diffusive Reaction. Applied Physics Letters, 110, Article ID: 072408. https://doi.org/10.1063/1.4976576
Olive Mendez, S.F., Petit, M., Ranguis, A., Le Thanh, V. and Michez, L. (2018) From the Very First Stages of Mn Deposition on Ge(001) to Phase Segregation. Crystal Growth & Design, 18, 5124-5129. https://doi.org/10.1021/acs.cgd.8b00558
Kalvig, R., Jedryka, E., Wojcik, M., Petit, M. and Michez, L. (2020) Selective Modification of the Unquenched Orbital Moment of Manganese Introduced by Carbon Dopant in Epitaxial Mn5Ge3C0.2/Ge(111) Films. Physical Review B, 101, Article ID: 094401. https://doi.org/10.1103/PhysRevB.101.094401
Le, T.G., Le Thanh, V. and Michez, L. (2020) Effect of Carbon on Structural and Magnetic Properties of Ge1-xMnx Nanocolumns. Bulletin of Materials Science, 43, 103. https://doi.org/10.1007/s12034-020-2082-z
Le, T.G., Dau, M.T., Le Thanh, V., Nam, D.N.H., Petit, M., Michez, L. and Khiem, N.V. (2012) Growth Competition between Semiconducting Ge1-xMnx Nanocolumns and Metallic Mn5Ge3 Clusters. Advances in Natural Sciences: Nanoscience and Nanotechnology, 3, Article ID: 025007. https://doi.org/10.1088/2043-6262/3/2/025007
Jamet, M., Barski, A., Devillers, T., Poydenot, V., Dujardin, R., Bayle-Guillemaud, P., Rothman, J., Bellet-Amalric, E., Marty, A. and Cibert, J. (2006) High-Curie-Temperature Ferromagnetism in Self-Organized Ge1-xMnx Nanocolumns. Nature Materials, 5, 653-659. https://doi.org/10.1038/nmat1686
Devillers, T., Jamet, M., Barski, A., Poydenot, V., Bayle-Guillemaud, P., Bellet-Amalric, E., Cherifi, S. and Cibert, J. (2007) Structure and Magnetism of Self-Organized Ge1-xMnx Nanocolumns on Ge(001). Physical Review B, 76, Article ID: 205306. https://doi.org/10.1103/PhysRevB.76.205306
Le, T.G. and Dau, M.T. (2016) Vertical Self-Organization of Ge1-xMnx Nanocolumn Multilayers Grown on Ge(001) Substrates. Modern Physics Letters B, 30, Article ID: 1650269. https://doi.org/10.1142/S0217984916502699
Le, T.G. (2015) Direct Structural Evidences of Epitaxial Growth Ge1-xMnx Nanocolumn Bi-Layers on Ge(001). Materials Sciences and Applications, 6, 533-538. http://www.scirp.org/journal/msa https://doi.org/10.4236/msa.2015.66057
Tardif, S., Cherifi, S., Jamet, M., Devillers, T., Barski, A., Schmitz, D., Darowski, N., Thakur, P., Cezar, J.C., Brookes, N.B., Mattana, R. and Cibert, J. (2010) Exchange Bias in GeMn Nanocolumns: The Role of Surface Oxidation. Applied Physics Letters, 97, Article ID: 062510. https://doi.org/10.1063/1.3476343