Recently, spin-transfer switching of magnetic tunnel junctions (MTJ's) has become a very active area of research. It is theoretically postulated that using perpendicular magnetic anisotropy materials will substantially reduce the critical current density for switching, resulting in lower energy devices, while keeping the thermal stability high. A range of perpendicular anisotropy material systems, including (i) multilayers, (ii) crystalline alloys, and (iii) amorphous alloys have been intensively studied in this dissertation. The surface and bulk anisotropy, damping parameter, and structural properties of these material systems have been investigated. Magnetic tunnel junctions based on some of these perpendicular material schemes have been fabricated, and their transport properties have been measured and related to the anisotropy. We have found several promising approaches to magnetic tunnel junctions utilized in spin-torque transfer random access memory (STT-RAM).