COMPOSITION DEPENDENCES OF KERR ROTATIONS IN MNBI AND MNBIAL FILMS

Composition dependences of MnBi and Al-doped MnBi films have been inve stigated. It has been found that the crystal growth and Kerr rotation theta(K) of MnBi depend sensitively on the composition ratio Mn/Bi. Th e optimum ratio is 55/45, where a strong c-axis orientation and a shar p peak in theta(K) appear. The maxiMUM theta(K) is 1.6-1.7-degrees at a wavelength of 700 nm at room temperature for glass substrates, and s carcely changes after doping with Al below 10%, but it decreases rapid ly because the growth of MnAl becomes dominant when the Al content exc eeds 10%. Doping with small amounts of Al is believed to obstruct the growth of the MnBi crystal and therefore results in a reduction in gra in size.