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Phase diagrams of Ni2+xMn1-xGa Heusler alloys from Hubbard Hamiltonian with account of Jahn-Teller effect

Published online by Cambridge University Press:  25 March 2011

Mikhail A. Zagrebin ,
Vasiliy D. Buchelnikov ,
Sergey V. Taskaev  and
Natal’ya Yu. Fedulova
Mikhail A. Zagrebin
Affiliation:
Chelyabinsk State University, 129 Brat’ev Kashirinykh Str., Chelyabinsk, 454001, Russia
Vasiliy D. Buchelnikov
Affiliation:
Chelyabinsk State University, 129 Brat’ev Kashirinykh Str., Chelyabinsk, 454001, Russia
Sergey V. Taskaev
Affiliation:
Chelyabinsk State University, 129 Brat’ev Kashirinykh Str., Chelyabinsk, 454001, Russia
Natal’ya Yu. Fedulova
Affiliation:
Chelyabinsk State University, 129 Brat’ev Kashirinykh Str., Chelyabinsk, 454001, Russia
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Abstract

In this work a microscopic Hamiltonian is investigated using the Hubbard model for a ferromagnet with two degenerate bands, taking into account the Jahn-Teller effect. A macroscopic free energy is obtained from the microscopic Hubbard Hamiltonian. All free energy coefficients depend on microscopic parameters: temperature T and composition x. As a result of analytical minimization of free energy, phase diagrams are numerically constructed. It is shown that at certain values of parameters on the phase diagrams there are thermodynamic paths which correspond to experimentally observed sequences of phase transitions. Using density of states spectra for different compositions x the T-x phase diagram is numerically constructed. This phase diagram can theoretically explain experimentally observed behavior of the temperatures of phase transitions.

Keywords

ferromagneticphase transformationalloy
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1310: Symposium FF – Magnetocalorics and Magnetic Cooling , 2011 , mrsf10-1310-ff03-08
Copyright
Copyright © Materials Research Society 2011

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References

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