Journal of Magnetism and Magnetic Materials 285 (2005) 279–289 Inﬂuence of thickness on microstructural and magnetic properties in Fe 3 O 4 thin ﬁlms produced by PLD A. Bollero Ã , M. Ziese, R. Ho¨hne, H.C. Semmelhack, U. Ko¨hler, A. Setzer, P. Esquinazi Department of Superconductivity and Magnetism, University of Leipzig, Linne´str. 5, 04103 Leipzig, Germany Received 18 May 2004; received in revised form 4 August 2004 Available online 11 September 2004 Abstract The pulsed laser deposition technique has been used to produce magnetite (Fe 3 O 4 ) ﬁlms with thickness ranging from 26to320nmgrownonMgAl 2 O 4 (100) substrates. Microstructural characterisation of the ﬁlms has revealed enlarged grains with increasing thickness, i.e. deposition time. Magnetisation hysteresis loops have been measured at different temperaturesintherange25–300Kforthreesamples:twoﬁlmswiththicknessof26and320nmdepositedonMgAl 2 O 4 (100) and, for comparison, a 30nm thick ﬁlm deposited on MgO (100). The evolution of the remanence and the coercivity with temperature shows signiﬁcant differences between the thinner ﬁlms and the thicker one which are explained in terms of the effect of the interfacial strain as well as the inﬂuence of the deposition time on the grain sizes and the variation in the density of antiphase boundaries. All the studied ﬁlms exhibit a minimum of the coercivity at about 130K, the temperature at which the magnetocrystalline anisotropy constant K 1 vanishes for the bulk material. r 2004 Elsevier B.V. All rights reserved. PACS: 75.70.i Keywords: Magnetite; Thin ﬁlms; Laser ablation; Magnetic properties 1. Introduction The pulsed laser deposition technique (PLD) is an effective method to produce high-quality mag- netite (Fe 3 O 4 ) ﬁlms. Masterson et al. [1] deposited single phase polycrystalline magnetite by this technique and Kleint et al. [2] prepared ﬁlms with high epitaxial quality on MgO substrates. This latter publication showed a shift in the Verwey transition temperature, T v , to lower values decreas- ing the ﬁlm thickness, which was attributed to straineffects.Senaetal. [3] observedthesameeffect with the result that the transition was completely eliminated for ﬁlms with a thickness lower than ARTICLE IN PRESS www.elsevier.com/locate/jmmm 0304-8853/$-see front matter r 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.jmmm.2004.08.004 Ã Corresponding author. Tel: +49-341-9732766; fax: +49- 341-9732769 E-mail address: a.bollero@uni-leipzig.de (A. Bollero).