关键词: 铁磁形状记忆合金/
结构转变/
磁性/
MnNiGa
English Abstract
Influences of Ga content on the structure and magnetic properties of Mn2 -xNiGa1+x alloys
Liu Hong-Yan,Liu Zhu-Hong,
Li Ge-Tian,
Ma Xing-Qiao
1.Department of Physics, University of Science and Technology Beijing, Beijing 100083, China
Fund Project:Projected supported by the 44th Scientific Research Foundation for Returned Overseas Chinese Scholars of State Education Ministry and the Fundamental Research Funds for the Central Universities, China (Grant No. FRF-BR-14-025A).Received Date:15 September 2015
Accepted Date:28 November 2015
Published Online:05 February 2016
Abstract:The structure magnetism and ordering transition of the ferromagnetic shape memory alloy Mn2 -xNiGa1+xhave been systematically studied in this paper. With increasing Ga content, the structure of the parent phase Mn2 -xNiGa1+x is transformed from Hg2CuTi-type to Cu2MnAl-type Heusler alloy gradually. Its lattice constant increases first and then decreases, reaching its maximum at x=0.3. The sample displays both the primary phase of Heusler and the Ni2In-type hexagonal phase in precipitate form when x lies in the range of 0.3-0.8. The Curie temperature of the primary phase of Heusler alloy Mn2 -xNiGa1+x reduces gradually from 590 K for Mn2NiGa to about 220 K for Ga2MnNi with the decrease of the exchange interaction between 3d electrons in the transition metals. However, the variation of Curie temperature of Ni2In-type hexagonal phase is gentle. The separation of Curie temperatures between the Ni2In-type hexagonal phase and the primary phase of Heusler occurs when x lies in the range from 0.6 to 0.8. Substitution of Mn by Ga has a significant influence on the coupling interaction among various atoms, leading to first increasing and then decreasing of the saturated magnetization of Mn2 -xNiGa1+x at low temperatures. That is, the saturated magnetization will rise for x0.4 and drops sharply for x0.4. Results of differential scanning calorimeter show that the melting temperature decreases gradually as x increases. Meanwhile, the transition temperature from parent phase (B2) to Heusler phase decreases first and increases later.
Keywords: ferromagnetic shape memory alloys/
structural transition/
magnetism/
MnNiGa
