Low-Temperature Phase <italic>c</italic>-axis Oriented Manganese Bismuth Thin Films With High Anisotropy Grown From an Alloy Mn55Bi45Target

Abstract

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/cm3 (0.60 MA/m). A magnetic uniaxial anisotropy energy density of $\sim 1.86 {\cdot 10^{7}}$ erg/cm3 (~1.86 MJ/m3) 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 Mn55Bi45 target is an important step toward facilitating the synthesis of multilayers for spintronics or in an exchange spring magnet configuration.