Low-Temperature Phase c-axis Oriented Manganese Bismuth Thin Films With High Anisotropy Grown From an Alloy Mn55Bi45 Target

Manganese bismuth thin films were deposited from a Mn55Bi45 (at.%) alloy target onto glass substrates at room temperature using dc magnetron sputtering. The ferromagnetic low-temperature phase (LTP) of MnBi was formed through a subsequent vacuum annealing step. The resulting thin films were highly c-axis textured. Magnetic measurement shows a maximum saturation magnetization of 600 emu/cm
³
(0.60 MA/m). A magnetic uniaxial anisotropy energy density of ~1.86·10
⁷
erg/cm
³
(~1.86 MJ/m
³
) was measured by torque magnetometry. The coercive field has a positive temperature coefficient and reaches 12 kOe (1.2 T) and 14 kOe (1.4 T) at 300 K for the out-of-plane and in-plane direction, respectively. Density functional theory calculations have confirmed that the magnetocrystalline anisotropy energy increases with increasing temperature as a result of a spin-reorientation occurring around 100 K. Growing LTP MnBi thin films directly from an alloy Mn
₅₅
Bi
₄₅
target is an important step toward facilitating the synthesis of multilayers for spintronics or in an exchange spring magnet configuration.