Magnetic Properties Of Organic Composite Granular Films, The Hall Effect And Magneto-optical Effect

Magnetic granular films consist of single-domain ferromagnetic granules embedded in an immiscible medium have been extensively studied recently.Because of the unique microstructure,many interesting and potentially useful phenomena have been observed in granular films in the two past decades.Giant magnetoresistance (GMR) and giant Hall effects(GHE) have been found and studied systematically. Besides,considerable attention has also been paid to the study of the magneto-optical Kerr effect(MOKE) due to its practical application in high density magneto-optic (MO) recording.On the other hand,organic spintronics attracted a lot of interest due to the advantage of organic semiconductor(such as inherent lattice flexibility and long spin coherence) and its potential applications recently.During the past few years, remarkable progress has been achieved in this field.While until now,the optical properties and MOKE in FM/OSE nano-composite film has not been reported.In this thesis,the preparation,Hall effect and Magneto-optical Kerr effect of magnetic metal-organic semiconductor granular films were been investigated.1,The Hall effect in magnetic metal/OSC granular films.A series of Co_x(Alq3)_1-x granular film samples were prepared using co-evaporating technique.Large Hall effects were observed in Co_x(Alq₃)_1-x granular film samples.In the x=0.37 sample,the Hall resistivity reaches 4.37×10⁴μΩ-cm at 15K with the applied field of 10KOe.The temperature and fraction dependence of Hall resistivity were investigated.The quantum coherence effect of granular system is considered to account for the enhanced Hall effects.Besides,the Hall effects in Co-TPD granular films were also investigated.2,The Hall effect in magnetic metal/OSC granular films.The Magneto-optical Kerr effect and optical character of Co-Alq₃ granular films were studied.Obvious Kerr effect was observed in samples with large component of magnetic material.With x rises,the Kerr rotation angle(θ_k) increases and the peak are slightly shifted toward long wavelength.Optical properties were investigated to understand the mechanism of Kerr effect in the samples.The magneto-optical effects of Fe-Alq₃ and Fe-TPD granular films were also studied.