Studies on preparation and properties of low temperature phase of MnBi prepared by electrodeposition

Abstract

MnBi alloy with low-temperature phase (LTP) is a promising candidate as rare-earth-free permanent magnet for its high intrinsic coercivity and the unique positive temperature coefficient. Many works have investigated on the preparation of the LTP-MnBi using physical methods, while there are few reports about the successful fabrication using electrodeposition method although this low cost process has been used for many material preparations so far. The main difficulty is the large negative reduction potential of manganese ions and on the basis the big difference between the reduction potentials of manganese ions and bismuth ions. In this paper, we reduced the reduction potentials of manganese ions and bismuth ions firstly and on this basis, the MnBi films with different ratios of manganese and bismuth were prepared using different deposited potentials. After annealed treatment of 380 °C, there appears the low temperature phase in XRD pattern for the sample in which the ratio of manganese and bismuth is 54:46. This is the first report in electrodeposited method so far and the corresponding coercivity reaches 1450 Oe measured by the physical property measurement system (PPMS).