Regensburg 2010 – wissenschaftliches Programm
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KR: Fachverband Kristallographie
KR 10: Poster: Multiferroics (with MA, DF, KR, DS)
KR 10.63: Poster
Dienstag, 23. März 2010, 10:45–13:45, Poster A
Origin of the tetragonal distortion in Fe-Pd shape memory alloys — •Ingo Opahle1, Klaus Koepernik2, Ulrike Nitzsche2, and Manuel Richter2 — 1Institut für Theoretische Physik, Universität Frankfurt, 60438 Frankfurt/Main, Germany — 2IFW Dresden, P.O.B. 270016, D-01171 Dresden, Germany
Magnetic shape memory alloys (MSMA) have attracted considerable attention as materials for actuator and sensor applications, due to large magnetically induced strains of up to 10%. A promising MSMA is disordered Fe70Pd30 with an induced strain of about 6% and a relatively high blocking stress.
We have calculated the electronic structure of disordered Fe-Pd alloys [1] in the framework of density functional theory using the full potential local orbital (FPLO) code. The origin of the tetragonal distortion in these completely disordered alloys is found to be a Jahn-Teller like effect, which allows the system to reduce its band energy in a narrow composition range. In this composition range, the energy landscape along the Bain path is found to be flat, in agreement with a large tunability of strain observed in epitaxial films, covering most of the Bain path from fcc to bcc [2]. On the basis of our results, we discuss the prospects for an optimization of the alloys’ properties by adding third elements, including effects on the magneto-crystalline anisotropy energy.
[1] I. Opahle et al., Appl. Phys. Lett. 94 (2009) 072508.
[2] J. Buschbeck et al., Phys. Rev. Lett. 103 (2009) 216101.