Magnetic and Magneto-Optical Properties of MnAI Alloyed Film

MnAl films, prepared with an Mn/Al multilayer structure by vacuum evaporation, were studied. In the Mn content range of 31 to 40 at%, films became ferromagnetic (τ phase) on annealing at from 220 to 420°C. They show the same X-ray diffraction lines of the fct (Cu-Au I) structure as do bulk MnAl alloys, although the range of Mn contents resulting in the τ phase is quite different, at 51 to 59 at%, from that for the bulk material. In these films, the τ phase is intermixed with a nonmagnetic η phase below 34 at% Mn, and with a ß phase above 36 at% Mn. The M
_s
changes with the Mn content, and shows a maximum of approximately 330 emu/cm
³
at about 36 at% Mn. The coercivity H
_c
increases from 1 to 6 kOe with increasing Mn content. The Kerr angle θ
_K
increases with decreasing wavelength λ, reaching a value of about 0.17° at 400 nm, while the reflectivity R has a value of above 40% in the visible wavelength range.