Effects of grain boundary width and crystallite size on conductivity and magnetic properties of magnetite nanoparticles
Tóm tắt
The structural, electrical, and magnetic properties of magnetite nanoparticles, with crystallite sizes 30, 40, and 50 nm, are studied. These crystallite sizes correspond to average particle sizes of 33, 87, and 90 nm, respectively, as determined by TEM. By HRTEM images, it is observed that grain boundary widths decrease as crystallite size increases. Electrical and microstructural properties are correlated based on the theoretical definition of charging energy. Conduction phenomena are investigated as a function of grain boundaries widths, which in turn depend on crystallite size: the calculations suggest that charging energy has a strong dependence on crystallite size. By zero-field-cooling and susceptibility measurements, it is observed that Verwey transition is crystallite size dependent, with values ranging from 85 to 95 K. In addition, a kink at the out-phase susceptibility curves at 35 K, and a strong change in coercivity is associated to a spin-glass transition, which is independent of crystallite size but frequency dependent. The activation energy associated to this transition is calculated to be around 6–7 meV. Finally, magnetic saturation and coercivity are found to be not significantly affected by crystallite size, with saturation values close to fine powders values. A detailed knowledge on the effects of grain boundary width and crystallite size on conductivity and magnetic properties is relevant for optimization of materials that can be used in magnetoresistive devices.
Tài liệu tham khảo
Balanda M et al (2005) Magnetic AC susceptibility of stoichiometric and low zinc doped magnetite single crystal. Eur Phys J B 43:201–212
Batlle X, Labarta A (2002) Finite-size effects in fine particles: magnetic and transport properties. J Phys D Appl Phys 35:R15–R42
Cabrera L, Gutierrez S, Menendez N, Morales MP, Herrasti P (2008) Magnetite nanoparticles: electrochemical synthesis and characterization. Electrochim Acta 53:3436–3441
Coey JMD (1999) Powder magnetoresistance. J Appl Phys 85:5576–5581
Coey JMD (2010) Magnetism and magnetic materials. Cambridge University Press, New York
Crespo P et al (2013) Magnetism in nanoparticles: tuning properties with coatings. J Phys Condens Matter 25:484006
Cullity BD, Graham CD (2009) Introduction to magnetic materials, 2nd edn. IEEE Press; Wiley, Hoboken
Dézsi I, Fetzer C, Gombkoto A, Szucs I, Gubicza J, Ungar T (2008) Phase transition in nanomagnetite. J Appl Phys 103:104312
García J, Subías G (2004) The Verwey transition—a new perspective. J Phys Condens Matter 16:R145–R178
Gonzalez-Fernandez MA et al (2009) Magnetic nanoparticles for power absorption: optimizing size, shape and magnetic properties. J Solid State Chem 182:2779–2784
Goya GF, Berquo TS, Fonseca FC, Morales MP (2003) Static and dynamic magnetic properties of spherical magnetite nanoparticles. J Appl Phys 94:3520–3528
Hernando A (1999) Magnetic properties and spin disorder in nanocrystalline materials. J Phys Condes Matter 11:9455–9482
Holland TJB, Redfern SAT (1997) Unit cell refinement from powder diffraction data: the use of regression diagnostics. Mineral Mag 61:65–77
Inoue J (2009) GMR, TMR and BMR. In: Shinjo T (ed) Nanomagnetism and spintronics. Elsevier, Oxford, pp 15–92
Janů Z, Hadač J, Švindrych Z (2007) Glass-like and Verwey transitions in magnetite in details. J Magn Magn Mater 310:e203–e205
Knobel M, Nunes WC, Socolovsky LM, De Biasi E, Vargas JM, Denardin JC (2008) Superparamagnetism and other magnetic features in granular materials: a review on ideal and real systems. J Nanosci Nanotechnol 8:2836–2857
Kodama RH, Berkowitz AE, McNiff EJJ, Foner S (1997) Surface spin disorder in ferrite nanoparticles. J Appl Phys 81:5552
Koksharov YA (2009) Magnetism of nanoparticles: effects of size, shape, and interactions. In: Gubin SP (ed) Magnetic nanoparticles. Wiley, Weinheim, pp 197–254
Kolesnichenko VL (2009) Synthesis of nanoparticulate magnetic materials. In: Gubin SP (ed) Magnetic nanoparticles. Wiley, Weinheim, pp 25–58
Lopez Maldonado KL, de la Presa P, Flores Tavizon E, Farias Mancilla JR, Matutes Aquino JA, Hernando Grande A, Elizalde Galindo JT (2013) Magnetic susceptibility studies of the spin-glass and Verwey transitions in magnetite nanoparticles. J Appl Phys 113:17E132
Lu ZL et al (2006) Large low-field magnetoresistance in nanocrystalline magnetite prepared by sol–gel method. J Phys Chem B 110:23817–23820
Macdonal JR, Johnson WB (2005) Fundamentals of impedance spectroscopy. Wiley, Hoboken
Mi WB, Shen JJ, Jiang EY, Bai HL (2007) Microstructure, magnetic and magneto-transport properties of polycrystalline Fe3O4 films. Acta Mater 55:1919–1926
Ogale SB, Ghosh K, Sharma RP, Greene RL, Ramesh R, Venkatesan T (1998) Magnetotransport anisotropy effects in epitaxial magnetite (Fe3O4) thin films. Phys Rev B 57:7823–7828
Psarras GC, Manolakaki E, Tsangaris GM (2003) Dielectric dispersion and ac conductivity in-iron particles loaded-polymer composites. Compos A Appl Sci Manuf 34:1187–1198
Sarkar D, Mandal M, Mandal K (2012) Domain controlled magnetic and electric properties of variable sized magnetite nano-hollow spheres. J Appl Phys 112:064318
Team GS (1999) Digital micrograph (TM), 3.7.1 edn. Gatan Inc, Pleasanton
Venkatesan M, Nawka S, Pillai SC, Coey JMD (2003) Enhanced magnetoresistance in nanocrystalline magnetite. J Appl Phys 93:8023
Vergés A, Costo R, Roca AG, Marco JF, Goya GF, Serna CJ, Morales MP (2008) Uniform and water stable magnetite nanoparticles with diameters around the monodomain–multidomain limit. J Phys D Appl Phys 41:134003
Walz F (2002) The Verwey transition—a topical review. J Phys Condes Matter 14:R285–R340
Zeleňáková A, Kováč J, Zeleňák V (2010) Magnetic properties of Fe2O3 nanoparticles embedded in hollows of periodic nanoporous silica. J Appl Phys 108:034323
Zhang X-Y, Chen Y, Li Z-Y (2007) AC magnetotransport property enhancement of Fe3O4 particles by modifying tunnelling barrier. J Phys D Appl Phys 40:326–330
Zhou H, Yi R, Li J, Su Y, Liu X (2010) Microwave-assisted synthesis and characterization of hexagonal Fe3O4 nanoplates. Solid State Sci 12:99–104