Friday, May 5, 2006, 11:00 am — Small seminar room, Bldg. 510
I will report on martensitic transitions and magnetic properties of Ni-Mn-X Heusler alloys, with X=Ga, Sn, In, and Sb. While for X = Ga the magnetic
moment of the martensite phase is higher than that of the austenite phase, for
X = Sn and In, it is found that the magnetic moment of the martensite phase
is lower than that of the austenite phase. Since the application of magnetic
field stabilizes the phase with the higher magnetic moment, the martensitic
transition temperature shifts to lower temperatures in the presence of a field
conversely to what happens in the prototype Ni-Mn-Ga. For the alloys men-
tioned above, such field induced effects are strong within limited composition
ranges making it possible to induce a reverse martensitic transition by simply
applying a moderate magnetic field. In this case, it is possible to achieve mag-
netic shape memory, not related to the re-orientation of martensite variants
but rather by the disappearance of these variants caused by the magnetic
field induced reverse transformation. This mechanism is fully reversible. Another significant property related to the decrease in the magnetic moment
at the martensitic transition is the so-called inverse magnetocaloric effect.
These alloys exhibit the unusual property of cooling when a magnetic field is
applied adiabatically.
Hosted by: Steve Shapiro
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