Magnetic and magnetotransport properties of ZnxFe3-xO4-y thin films

Nathalie Jedrecy (1) , Christian Hebert (1) , J. Perriere (1) , M. Nistor (2) , E. Millon (3)

1 INSP - Institut des Nanosciences de Paris
2 National Institute for Lasers, Plasma, and Radiation Physics - INFLPR (ROMANIA)
3 GREMI - Groupe de recherches sur l'énergétique des milieux ionisés

We present a detailed magnetic and magnetotransport investigation of spinel zinc ferrite ZnxFe3-xO4-y (0.1 <= x <= 0.6) thin films grown by pulsed laser deposition on various substrates. The films are ranging from polycrystalline to (001)- or (111)-oriented. It is shown associating magnetic and resistivity measurements to x-ray and ion beam scattering analyses that the magnetic and electrical properties are tightly linked to the chemical composition and crystallinity/microstructure of the films, as they result from the choice of substrate and growth conditions. The use of oxidizing conditions (O-2 pressure approximate to 10(-4)-10(-2) mbar) is highly detrimental to the crystalline quality and thus to the ferromagnetism. On the contrary, a partial O-2 pressure of 3 x 10(-7) mbar combined to a growth temperature of 500 degrees C allows obtaining ZnxFe3-xO4-y films displaying very good ferromagnetic features. The SiO2/Si substrates, promoting (111) growth without interfacial effects, lead to better film properties than Al2O3(0001), MgO(001), or SrTiO3(001) substrates: higher Curie temperatures and higher magnetization values (similar to 490 kAm(-1)) at room temperature. Above a Verwey-type critical temperature, a thermally activated spin polarized charge transport is observed, while in the low temperature range, the resistivity is well described by the variable range hopping model. However, the negative magnetoresistance response at low field remains modest and a monotonous decrease with increasing magnetic field is observed. We show that a steeper low field magnetoresistance decrease may be obtained in polycrystalline stoichiometric layers formed by a specific two-step growth process, which significantly reduces the density of grain/antiphase boundaries. (C) 2014 AIP Publishing LLC.

Domaines: Matière Condensée [cond-mat]; Science des matériaux [cond-mat.mtrl-sci]

Nathalie Jedrecy, Christian Hebert, J. Perriere, M. Nistor, E. Millon. Magnetic and magnetotransport properties of ZnxFe3-xO4-y thin films. Journal of Applied Physics, 2014, 116 (21), pp.213903. ⟨10.1063/1.4903211⟩. ⟨hal-01240511⟩