language: en

[Confidential: not for distribution. Submitted to IOP Publishing for peer review]

15 December 2009

[CVD synthesis of polycrystalline magnetite thin films: structural, magnetic, and magnetotransport properties]

CVD synthesis of polycrystalline magnetite thin films: structural, magnetic, and magnetotransport properties

by R Mantovan 1,3 , A Lamperti 1 , M Georgieva 1 , G Tallarida 1 and M Fanciulli 1,2
1 Laboratorio Nazionale MDM CNR-INFM,
Via C. Olivetti 2, 20041 Agrate Brianza (MI), Italy.
2 Dipartimento di Scienza dei Materiali, Università di Milano
Bicocca, Milano, Italy
E-mail: roberto.mantovan@mdm.infm.it

Abstract. Magnetite (Fe 3 O 4 ) is predicted to be half metallic at room temperature and it shows the highest Curie temperature among oxides. The use of Fe 3 O 4 thin films is therefore promising spintronic devices such as magnetic tunnel junctions and magnetoresistive sensors. The structural, magnetic, and magnetotransport properties of magnetite are reported to be strongly dependent on the growth conditions. We have developed a very simple deposition chamber for growing thin magnetite films via a chemical vapor deposition process based on the Fe 3 (CO) 12 carbonyl precursor. The structural, morphological and magnetic properties of the as deposited Fe 3 O 4 films have been investigated by means of time of flight secondary ion mass spectrometry, grazing incidence X-ray diffraction, X-ray reflectivity, atomic force microscopy, conversion electron Mössbauer and superconducting quantum interference device magnetometry. Magnetotransport measurements show magnetoresistance up to -2.4% at room temperature at the maximum applied field of 1.1 T. Resistivity measurements in the 100-300 K temperature range reveal that the magnetotransport properties of the Fe 3 O 4 films are governed by inter-granular tunneling of the spin polarized electrons. The spin polarization is estimated to be around -16%. A possible route for increasing the spinpolarized performances of our magnetite films is proposed. We have also deposited Fe 3 O 4 stacks by using a combined chemical vapor- and atomic layer- deposition process. The trilayer's hysteresis curve evidences the presence of two distinct switching fields making it promising for magnetite-based magnetic tunnel junction applications.

[3 Author to whom any correspondence should be addressed.]

[CVD synthesis of polycrystalline magnetite thin films: structural, magnetic, and magnetotransport properties 2]

1. Introduction