Crystal Structure and Magnetic Properties of Mn-Al-Ni Ferromagnetic Films

Mn
_60-x
Al
₄₀
Ni
_x
ternary films were prepared by dc magnetron sputtering and their crystallographic characteristics and magnetic properties were investigated. The τ phase was synthesized at Ni contents below 7 at%. The lattice constant a increased from 3.98 Å to 4.12 Å, and c decreased from 3.48 Å to 3.21 Å, as a result of increasing the Ni substitution. The M
_s
of the τ-phase films increased with increasing Ni substitution up to an Ni content of a few percent. The maximum values for M
_s
and Hc, 240 emu/cc and 2.9 kOe respectively, were obtained at an Ni content of 3 at%. The high H
_c
was due to the increased asymmetry of the tetragonal structure. The magnetic anisotropy of τ-phase films was caused mainly by the preferential orientation of the c-axis of the tetragonal crystallites.