Influence of annealing and phase decompostion on the magnetostructural transitions in Ni50Mn39Sn11

Journal Article · Fri Feb 13 04:00:00 EST 2009 · Journal of Applied Physics

OSTI ID:977176

Yuhasz, W; Schlagel, D; Xing, Q; Dennis, K; McCallum, R; Lograsso, T

Magnetic and structural transitions in the Ni{sub 50}Mn{sub 50-x}Sn{sub x} (x=10-25) ferromagnetic shape memory alloys are currently of interest. As in Ni-Mn-Ga, these alloys feature high-temperature austenite and low-temperature martensite phases, where the magnetic state is strongly composition dependent. To study the role of chemical ordering in fine-tuning their magnetostructural properties, they were first annealed for 4 weeks/1223 K to achieve structural and compositional homogeneity, and were then further annealed for 1 week ({approx}150 K below the reported B2 to L2{sub 1} transition) at 773 K to increase the degree of chemical ordering. For x=11, this anneal resulted in a dramatic change in the magnetic ordering temperature. Following the 1223 K anneal, the sample exhibited ferromagnetic ordering at 140 K. After the 773 K anneal, the ferromagnetic transition is at 350 K, a characteristic of the ferromagnetic austenite phase with 15 < x < 25. Consistent with the magnetization data, transmission electron microscopy examination confirms that the alloy decomposed into two phases with x=20 and 1. From this result one can conclude that the martensitic transformation occurs only in those compositions where the single phase L2{sub 1} has been retained in a metastable state on cooling.

• Research Organization: Ames Laboratory (AMES), Ames, IA (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: AC02-07CH11358
• OSTI ID: 977176
• Report Number(s): IS-J 7481
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 07A921 Vol. 105; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ALLOYS
ANNEALING
AUSTENITE
MAGNETIZATION
MARTENSITE
METASTABLE STATES
SHAPE
TRANSFORMATIONS
TRANSMISSION ELECTRON MICROSCOPY