Abstract
Thin films of ferromagnetic LTP-MnBi (Low Temperature Phase of MnBi) have been grown by magnetron sputtering onto quartz substrates. Two particular issues related to LTP-MnBi have been investigated: the strong influence of the growth temperature and the degradation of magnetic properties in time. The temperature dependence on the magnetic, morphological and microstructural properties has been investigated, evidencing drastic changes on the properties of MnBi with small temperature variations. By inducing a gradient of temperature during the growth, two well differentiated regions with different morphology and crystal structure have been observed in a MnBi film sample. On the other hand, aging experiments performed in a different LTP-MnBi sample has led to a notable decrease of 54% in the saturation magnetization after 6 days and a complete loss of ferromagnetic response after 4 months.
Highlights
In the last years, the scientific community has been making a great effort on developing new combinations of materials to overcome the problem on the scarcity of certain elements.1,2 For this purpose, the use of the ferromagnetic manganese based alloys has been proposed for certain applications as rare earth free permanent magnets, magnetic recording media and spintronic devices.3,4 Hard magnetic thin films with perpendicular magnetic anisotropy and high coercivity are attracting a lot of interest in spintronic devices and in MEMS (Magnetic Micromechanical Systems), including micro-motors, sensors and radiofrequency micro switches.5–8LTP-MnBi is a ferromagnetic intermetallic compound which crystallizes in the NiAs-type hexagonal crystal structure
We have focused on the reported anomalies of MnBi system
Two studies have been performed to understand the influence of temperature and time with the purpose of further understanding of MnBi anomalies
Summary
The scientific community has been making a great effort on developing new combinations of materials to overcome the problem on the scarcity of certain elements. For this purpose, the use of the ferromagnetic manganese based alloys has been proposed for certain applications as rare earth free permanent magnets, magnetic recording media and spintronic devices. Hard magnetic thin films with perpendicular magnetic anisotropy and high coercivity are attracting a lot of interest in spintronic devices and in MEMS (Magnetic Micromechanical Systems), including micro-motors, sensors and radiofrequency micro switches.. The MnBi system presents interesting anomalies that have not been completely understood One of these anomalies is the strong dependence of magnetic properties and crystal structure with the applied temperature during LTP-MnBi formation. Scitation.org/journal/adv up to highly coalesced textured film-like areas These microstructural variations determine the magnetic behavior, including the change in the easy axis direction and the possibility of varying coercivity from 4 to 16 kOe at room temperature. The type one of MnBi film (called MnBi-1) has been grown and subjected to a gradient temperature during LTP formation in order to analyze the temperature dependence on magnetic properties, morphology and crystal structure. Magnetic properties and crystal structure of a LTP-MnBi sample (called MnBi-2) have been studied over time in order to analyze aging effects
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