Magnetic and Structural Properties of Rapidly Quenched Tetragonal Mn3-xGa Nanostructures

• Published in: IEEE transactions on magnetics Vol. 49; no. 7; pp. 3277 - 3280
• Main Authors: HUH, Y, KHAREL, P, SHAH, V. R, KRAGE, E, SKOMSKI, R, SHIELD, J. E, SELLMYER, D. J
• Format: Conference Proceeding Journal Article
• Language: English
• Published: New York, NY Institute of Electrical and Electronics Engineers 01-07-2013
• Subjects: Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Other topics in materials science; Physics; permanent magnet; Magnetic anisotropy; melt-spun ribbons; Permanent magnets; Nanostructures; spintronic device; Microstructure; Heat treatments; Magnetic properties; Quenching
• ISSN: 0018-9464; 1941-0069
• DOI: 10.1109/TMAG.2013.2244856

Nanostructured Mn3-x Ga ribbons with x = 0, 0.4, 0.9 and 1.1 were prepared using arc-melting, melt-spinning and annealing. As-spun samples crystallized into hexagonal D0(19) and cubic L2(1) Heusler crystal structures based on the concentration of Mn in Mn3-xGa. Upon vacuum-annealing the samples at 450 degrees C for about 50 hours, both the hexagonal and cubic structures transformed into a tetragonal D0(22) structure. High-temperature x-ray diffraction and high-temperature magnetometry showed that the samples with low Mn content (Mn-1.9 Ga and Mn-2.1 Ga) retain their tetragonal structure up to 850 K but the samples with high Mn concentrations (Mn-2.6 Ga and Mn-3.0 Ga) undergo a structural phase transition from tetragonal to hexagonal phases around 800 K. The magnetic properties of Mn3-x Ga ribbons were very sensitive to Mn concentration, where the magnetization and anisotropy energy increased and the coercivity decreased as x increased from 0 to 1.1. Although the Curie temperatures of Mn-2.6 Ga and Mn-3.0 Ga samples could not be determined because of the structural phase transition, the Curie temperature decreased with increasing x in Mn3-x Ga. The maximum magnetization of 57 emu/g (300 emu/cm(3)) and the coercivity of 6.5 kOe were measured in the Mn-1.9 Ga and Mn-3.0 Ga ribbons, respectively.