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

• Published in: IEEE transactions on magnetics 2017-04, Vol.53 (4), p.1-6
• Main Authors: Sabet, S., Hildebrandt, E., Romer, F. M., Radulov, I., Zhang, H., Farle, M., Alff, L.
• Format: Article
• Language: English
• Subjects: Annealing; Bismuth; Coercivity; DC magnetron sputtering; Low temperature; low-temperature phase (LTP) MnBi; Magnetic anisotropy; Magnetic multilayers; magnetic thin films; Magnetism; Magnetization; Magnetometers; Magnetron sputtering; Manganese base alloys; Perpendicular magnetic anisotropy; rare-earth-free magnet; Saturation magnetization; Spintronics; Temperature measurement; Thin films
• ISSN: 0018-9464; 1941-0069
• DOI: 10.1109/TMAG.2016.2636817

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.