Interaction of phase transformation and magneto- and elastocaloric properties of Heusler alloys

2013 ◽  
Vol 1581 ◽  
Author(s):  
Peter Entel ◽  
Vladimir V. Sokolovskiy ◽  
Vasiliy D. Buchelnikov ◽  
Denis Comtesse ◽  
Mehmet Acet
Keyword(s):  
Monte Carlo ◽  
Shape Memory ◽  
Ab Initio ◽  
Heusler Alloys ◽  
Magnetic Ordering ◽  
Magnetic Behavior ◽  
Experimental Investigations ◽  
Driving Mechanism ◽  
Magnetic Shape Memory ◽  
Magnetic Exchange

ABSTRACTThe structural, electronic and magnetic properties of functional Ni-Mn-(Ga, In, Sn) and Pt-Ni-(Ga, Sn) alloys are studied by first-principles and Monte Carlo tools. The ab initio calculations give a basic understanding of the underlying physics which is associated with the complex magnetic behavior arising from the competition of ferro- and antiferromagnetic interactions for excess Mn atoms in the unit cell. We show that the resulting complex magnetic ordering is the driving mechanism of structural transformations and multifunctional properties of Heusler alloys associated with magnetic shape-memory, magnetocaloric and elastocaloric effects. The thermodynamic properties can be calculated by using the ab initio magnetic exchange parameters in finite-temperature Monte Carlo simulations. Entropy and specific heat changes associated with the magnetic changes and emergence of microstructure across the magnetostructural transition are pointed out. We show how to optimize the functional properties by tuning the compositional changes, for example, a magnetic shape-memory effect of more than 14% can be achieved in Pt-Ni-Mn-Ga alloys. The theoretical studies are accompanied by experimental investigations.

New Functional Magnetic Shape Memory Alloys from First-Principles Calculations

2009 ◽  
Vol 1200 ◽  
Author(s):  
Peter Entel ◽  
Mario Siewert ◽  
Antje Dannenberg ◽  
Markus Ernst Gruner ◽  
Manfred Wuttig
Keyword(s):  
Monte Carlo ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Ab Initio ◽  
First Principles ◽  
Magnetic Shape Memory ◽  
Phonon Softening ◽  
Ferromagnetic Shape Memory Alloys ◽  
Magnetic Exchange ◽  
Austenitic Phase

AbstractAn overview is given of new ferromagnetic Heusler alloys like Ni-Co-(Al, Ga, Zn), Co-Ni-(Al, Ga, Zn), Fe-Ni-(Al, Ga, Zn) and Fe-Co-(Al, Ga, Zn), which are compared with today's mostly investigated systems such as Ni-Mn-Z (Z = Al, Ga, In, Sn, Sb). The investigations are based on first-principles as well as Monte Carlo calculations. For some new systems, the simulations of atomic structure and magnetic and electronic properties allow to predict higher Curie and martensitic transformation temperatures than those of prototypical Ni-Mn-Z materials. Some of the new materials may be distinguished for devices which exploit the magnetic shape memory effect. Interestingly, in general, all off-stoichiometric alloys display competing antiferromagnetic correlations, which may be important for devices using the magnetocaloric effect. The Curie temperatures are obtained from Monte Carlo simulations using magnetic exchange parameters from ab initio calculations while the structural instability is inferred from local minima in the ab initio total energy curves as a function of the tetragonal distortion. The manifestation of phonon softening as a precursor of structural transformations is present in the austenitic phase of most of the calculated ferromagnetic shape-memory alloys. However, quite remarkably, we find that phonon softening is absent in a few systems such as Co2NiGa.

scholarly journals Structural and magnetic properties of heusler alloys Pd2MnZ (Z=Ga, Ge, As): AB INITIO study

2018 ◽  
Vol 185 ◽  
pp. 05007 ◽  
Author(s):  
Olga Miroshkina ◽  
Mikhail Zagrebin ◽  
Vladimir Sokolovskiy ◽  
Vasiliy Buchelnikov
Keyword(s):  
Monte Carlo ◽  
Magnetic Properties ◽  
Ab Initio ◽  
Magnetic Moments ◽  
Heusler Alloys ◽  
Magnetic Exchange ◽  
Valence Electrons ◽  
Martensitic State ◽  
Structural And Magnetic Properties ◽  
Exchange Parameters

In this work, we report results of ab initio and Monte Carlo investigations of structural and magnetic properties in a series of Heusler compositions Pd2MnZ (Z = Ga, Ge, As). It was found that for Pd2MnGa and Pd2MnAs, the stable martensitic state is realized on the contrast with Pd2MnGe. The equilibrium lattice parameters for the series of Pd2MnZ (Z = Ga, Ge, As) compounds increase with increasing the number of valence electrons per atom (e/a ratio). Having calculated total magnetic moments and magnetic exchange parameters from ab initio methods, the Curie temperature for Pd2Mn-based alloys has been estimated in the framework of Monte Carlo simulations of Heisenberg model.

Origin of anomalous cryogenic magnetic behavior in a Ni-Mn-based magnetic shape memory alloy

2017 ◽  
Vol 110 (13) ◽  
pp. 132402 ◽  
Author(s):  
X. M. Sun ◽  
D. Y. Cong ◽  
K.-D. Liss ◽  
Y. H. Qu ◽  
L. Ma ◽  
...  
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Magnetic Behavior ◽  
Magnetic Shape Memory ◽  
Magnetic Shape Memory Alloy

Composition-Dependent Basics of Smart Heusler Materials from First- Principles Calculations

2011 ◽  
Vol 684 ◽  
pp. 1-29 ◽  
Author(s):  
Peter Entel ◽  
Antje Dannenberg ◽  
Mario Siewert ◽  
Heike C. Herper ◽  
Markus E. Gruner ◽  
...  
Keyword(s):  
Shape Memory ◽  
First Principles ◽  
Density Functional ◽  
Elevated Temperatures ◽  
Heusler Alloys ◽  
Density Functional Theory Calculations ◽  
First Principles Calculations ◽  
Magnetic Shape Memory ◽  
Functional Theory ◽  
Magnetic Shape Memory Alloy

The structural and magnetic order are the decisive elements which vastly determine the properties of smart ternary intermetallics such as X2YZ Heusler alloys. Here, X and Y are transition metal elements and Z is an element from the III-V group. In order to give a precise prescription of the possibilities to optimize the magnetic shape memory and magnetocaloric effects of these alloys, we use density functional theory calculations. In particular, we outline how one may find new intermetallics which show higher Curie and martensite transformation temperatures when compared with the prototypical magnetic shape-memory alloy Ni2MnGa. Higher operation temperatures are needed for technological applications at elevated temperatures.

Ternary diagrams of magnetic properties of Ni-Mn-Ga Heusler alloys from ab initio and Monte Carlo studies

2019 ◽  
Vol 470 ◽  
pp. 64-68 ◽  
Author(s):  
Vladimir V. Sokolovskiy ◽  
Yulia A. Sokolovskaya ◽  
Mikhail A. Zagrebin ◽  
Vasiliy D. Buchelnikov ◽  
Alexey T. Zayak
Keyword(s):  
Monte Carlo ◽  
Magnetic Properties ◽  
Ab Initio ◽  
Heusler Alloys ◽  
Ternary Diagrams ◽  
Monte Carlo Studies

Ferromagnetic Shape Memory Heusler Alloys

2012 ◽  
Vol 189 ◽  
pp. 189-208 ◽  
Author(s):  
Vijay Srivastava ◽  
Kanwal Preet Bhatti
Keyword(s):  
Magnetic Properties ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Heusler Alloy ◽  
Heusler Alloys ◽  
Structural Similarity ◽  
Magnetic Shape Memory ◽  
Half Metallicity ◽  
Ferromagnetic Shape Memory

Although Heusler alloys have been known for more than a century, but since the last decade there has been a quantum jump in research in this area. Heusler alloys show remarkable properties, such as ferromagnetic shape memory effect, magnetocaloric effect, half metallicity, and most recently it has been shown that it can be used for direct conversion of heat into electricity. Heusler alloys Ni-Mn-Z (Z=Ga, Al, In, Sn, Sb), show a reversible martensitic transformation and unusual magnetic properties. Other classes of intermetallic Heusler alloy families that are half metallic (such as the half Heusler alloys Ni-Mn-Sb and the full Heusler alloy Co2MnGe) are attractive because of their high Curie temperature and structural similarity to binary semiconductors. Unlike Ni-Mn-Ga, Ni-Mn-In and Ni-Mn-Sn transform from ferromagnetic austenite to non-ferromagnetic martensite. As is consistent with the Clausius-Clapeyron equation, the martensitic phase transformation can be manipulated by a magnetic field, leading to possible applications of these materials enabling the magnetic shape memory effect, energy conversion and solid state refrigeration. In this paper, we summarize the salient features of Heusler alloys, like the structure, magnetic properties and potential application of this family of alloys in industry.

Ab initio modeling of martensitic transformations (MT) in magnetic shape memory alloys

2007 ◽  
Vol 310 (2) ◽  
pp. 2761-2763 ◽  
Author(s):  
P. Entel ◽  
M.E. Gruner ◽  
W.A. Adeagbo ◽  
C.-J. Eklund ◽  
A.T. Zayak ◽  
...  
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Ab Initio ◽  
Martensitic Transformations ◽  
Magnetic Shape Memory ◽  
Magnetic Shape Memory Alloys ◽  
Ab Initio Modeling

Magnetic ordering in magnetic shape memory alloy Ni-Mn-In-Co

2015 ◽  
Vol 92 (22) ◽  
Author(s):  
K. Ollefs ◽  
Ch. Schöppner ◽  
I. Titov ◽  
R. Meckenstock ◽  
F. Wilhelm ◽  
...  
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Magnetic Ordering ◽  
Magnetic Shape Memory ◽  
Magnetic Shape Memory Alloy

Shape Memory Alloys: A Summary of Recent Achievements

2008 ◽  
Vol 583 ◽  
pp. 21-41 ◽  
Author(s):  
Peter Entel ◽  
Vasiliy D. Buchelnikov ◽  
Markus E. Gruner ◽  
Alfred Hucht ◽  
Vladimir V. Khovailo ◽  
...  
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Shape Memory ◽  
Shape Change ◽  
Heusler Alloys ◽  
Systematic Change ◽  
Magnetic Shape Memory ◽  
Electronic Density ◽  
Modulated Phases ◽  
Modulated Structures

The Ni-Mn-Ga shape memory alloy displays the largest shape change of all known magnetic Heusler alloys with a strain of the order of 10% in an external magnetic field of less than one Tesla. In addition, the alloys exhibit a sequence of intermediate martensites with the modulated structures usually appearing at c/a < 1 while the low-temperature non- modulated tetragonal structures have c/a > 1. Typically, in the Ni-based alloys, the martensitic transformation is accompanied by a systematic change of the electronic structure in the vicinity of the Fermi energy, where a peak in the electronic density of states from the non-bonding Ni states is shifted from the occupied region to the unoccupied energy range, which is associated with a reconstruction of the Fermi surface, and, in most cases, by pronounced phonon anomalies. The latter appear in high-temperature cubic austenite, premartensite but also in the modulated phases. In addition, the modulated phases have highly mobile twin boundaries which can be rearranged by an external magnetic field due to the high magnetic anisotropy, which builds up in the martensitic phases and which is the origin of the magnetic shape memory effect. This overall scenario is confirmed by first-principles calculations.

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