STUDY OF MAGNETIC MATERIALS AT NANO SCALE

Abstract

The miniaturization of memory devices like hard disks, random access memories and their read heads has made the detailed study of magnetic materials at nano scale imperative. The characteristics of magnetic material are highly sensitive to different growth conditions, temperature and nature of neigbouring material, as a result the magnetic characteristics may be tailored. In this research work single Ni thin films sandwiched between Cu buffer layer and Cu capping layer are grown on Si(001) substrates by resistive heating in an ultra high vacuum chamber at different substrate temperature .The temperatures of substrate chosen for this study are 300K (room temperature) and very low temperature, approximately 30K. These thin films are grown with different Ni thickness ranging from 1nm to 10nm. A comparison of physical and magnetic properties of Ni thin films is done with respect to Ni thickness as well as with respect to the substrate temperature. Multilayers of Ni thin films are also grown. These multilayers are grown on Si(111) with a Cu buffer layer, a Cu spacer layer between the Ni layers and a Cu capping layer. The multilayers are grown with different Ni thicknesses, ranging from 1nm to 3nm, and with different Cu spacer layer thickness, ranging from 10nm to 20nm. A comparison of physical and magnetic characterization is done with respect to Ni thickness and with respect to different Cu spacer thickness. It is found that the thickness of the Ni thin film as well as the temperature of the substrate affects the physical and magnetic properties of the Cu/Ni/Cu/Si(001) samples. The variation in grain size of samples with different Ni thickness and different substrate temperature, shows different trend. Grain size of samples grown at low substrate temperature is larger. The values of saturation magnetization of different Ni thickness samples, grown at room temperature of substrate, increases with increase in Ni thickness. In Cu/Ni/Cu/Ni/Cu/Si(111) multilayers with different Ni thicknesses indicate that the grain size is affected by the thickness of the Ni film. The value of saturation magnetization is almost the same for different Ni thicknesses. Grain size is affected in multilayers with different Cu spacer layers as well. The saturation magnetization is nearly constant for different spacer layers with same Ni thickness. A shift in the hysteresis loop is also observed in the positive direction for most of the multilayers.