Comparative Study of Magnetization of Co Thin Films Deposited on Glass, GaAs (001) and Si (001) Substrates

The effect of surface induced anisotropy and interfacial anisotropy on the magnetic properties of Co thin films have been presented. The surface roughness of 100 nm Co film on both the glass and Si (001) substrate is found to be ~ 50 Oe. But the surface roughness of the same thick Co film on GaAs (001) substrate is enhanced to ~ 80 Oe. The enhancement of coercivity of Co thin film on GaAs (001) substrate is due to the special interaction between transition metal Co and GaAs (001). The anisotropy field due to the cobalt silicide interface is responsible for large saturation field required to saturate the Co/Si sample. The squareness of Co thin film on both the glass and GaAs (001) is ~ 1. On the other hand, it is reduced to 0.45 for Co/Si system. Both the surface induced and interfacial anisotropy fields influence the shape of the hysteresis loop

Magnetic and Magnetoresistive Properties of Ferromagnet/Semiconductor Hybrid Structures

Supervisor:Professor Hidenobu Hori材料科学研究科博

Effect of Cobalt Silicide Buffer Layer on Magnetic and Electrical Properties of Co Thin Films Deposited on Si, GaAs and Glass Substrates

Cobalt silicide layers have been grown by E‒beam evaporation of Co onto Si (100) substrate and subsequent thermal treatment at 673K for 5 hours. A fresh layer of 100 nm Co is deposited on the silicide layer (sample‒1). A thin layer of 5 nm Co have been deposited on GaAs (100) substrate and annealed at 673K for 5 hours. A fresh layer of 100 nm Co is deposited on 5 nm annealed Co buffer layer (sample‒2). 100 nm Co films have been grown on glass substrate for comparison. Magnetic properties of Co thin films have been studied by Vibrating sample magnetometer (VSM). Measurements of magnetic properties show that the coercivity is 580 Oe for sample‒1. The coercivity of the sample‒2 is 240 Oe. The coercivity of 100 nm as-deposited Co films on glass substrate is only 50 Oe and the coercivity increases up to 100 Oe after annealing at 673K for 5 hours. Electrical measurements show that the Sample-1 is metallic in nature but the Sample‒2 is semiconducting in nature. In X-ray diffraction measurement, the Co films grown on n-GaAs and Si substrates exhibited a polycrystalline hcp structure. XRD study of Co thin films grown on glass substrate show a microcrystalline hcp structure