Magnetocaloric and Shape-Memory Properties in Magnetic Heusler Alloys

2008 ◽  
Vol 52 ◽  
pp. 221-228 ◽  
Author(s):  
Antoni Planes ◽  
Lluís Mañosa ◽  
Xavier Moya ◽  
Jordi Marcos ◽  
Mehmet Acet ◽  
...  
Keyword(s):  
Shape Memory ◽  
Magnetocaloric Effect ◽  
Heusler Alloys ◽  
Length Scale ◽  
Martensitic Transition ◽  
Magnetic Domains ◽  
Magnetic Shape Memory ◽  
Uniaxial Magnetic Anisotropy ◽  
Shape Memory Properties ◽  
Applied Fields

In this paper, we discuss the magnetocaloric behavior of Ni-Mn-based Heusler alloys in rela- tion to their shape-memory and superelastic properties. We show that the magnetocaloric effect in these materials originates from two different contributions: (i) the coupling that is related to a strong uniaxial magnetic anisotropy and takes place at the length scale of martensite variants and magnetic domains (extrinsic effect), and (ii) the intrinsic microscopic magnetostructural coupling. The first contribution is intimately related to the magnetically induced rearrange- ment of martensite variants (magnetic shape-memory) and controls the magnetocaloric effect at small applied fields, while the latter is dominant at higher fields and is essentially related to the possibility of magnetically inducing the martensitic transition (magnetic superelasticity). The possibility of inverse magnetocaloric effect associated with these two contributions is also considered.

Recent Progress and Future Perspectives in Magnetic and Metamagnetic Shape-Memory Heusler Alloys

2013 ◽  
Vol 738-739 ◽  
pp. 391-399 ◽  
Author(s):  
Antoni Planes ◽  
Lluís Mañosa ◽  
Mehmet Acet
Keyword(s):  
Shape Memory ◽  
Heusler Alloys ◽  
Martensitic Transition ◽  
Future Perspectives ◽  
Magnetic Shape Memory ◽  
Strong Response ◽  
Complex Behaviour ◽  
First Case ◽  
Superelastic Effect ◽  
Magneto Resistance

Magnetic shape-memory properties refer to the ability of certain materials to show strong response in strain to an applied magnetic field. This strain is caused by either inducing the martensitic transition or rearranging martensitic variants. In the first, case a superelastic effect is possible, while in the second, the system is able to show the shape-memory effect. The complex behaviour displayed by these materials is mainly a consequence of a strong interplay between magnetism and structure which is driven by a martensitic transition. This interplay is the source of many other observed effects such as giant magneto-resistance, exchange bias and magnetocaloric effects. In this paper, we will overview the present state of the art, discuss present challenges and outline some future perspectives in the field.

Magnetic shape memory and giant magnetocaloric effect in Heusler alloys

2008 ◽  
Vol 72 (4) ◽  
pp. 527-528
Author(s):  
V. G. Shavrov ◽  
V. D. Buchelnikov ◽  
A. N. Vasilev ◽  
V. V. Koledov ◽  
S. V. Taskaev ◽  
...  
Keyword(s):  
Shape Memory ◽  
Magnetocaloric Effect ◽  
Heusler Alloys ◽  
Magnetic Shape Memory ◽  
Giant Magnetocaloric Effect

Effects of Annealing on Microstructure and Martensitic Transition of Ni-Mn-Co-In Ferromagnetic Shape Memory Alloys

2011 ◽  
Vol 674 ◽  
pp. 171-175
Author(s):  
Katarzyna Bałdys ◽  
Grzegorz Dercz ◽  
Łukasz Madej
Keyword(s):  
Electron Microscopy ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Smart Materials ◽  
Martensitic Transition ◽  
Magnetic Shape Memory ◽  
Ferromagnetic Shape Memory Alloys ◽  
Initial State ◽  
X Ray ◽  
Ferromagnetic Shape Memory

The ferromagnetic shape memory alloys (FSMA) are relatively the brand new smart materials group. The most interesting issue connected with FSMA is magnetic shape memory, which gives a possibility to achieve relatively high strain (over 8%) caused by magnetic field. In this paper the effect of annealing on the microstructure and martensitic transition on Ni-Mn-Co-In ferromagnetic shape memory alloy has been studied. The alloy was prepared by melting of 99,98% pure Ni, 99,98% pure Mn, 99,98% pure Co, 99,99% pure In. The chemical composition, its homogeneity and the alloy microstructure were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The phase composition was also studied by X-ray analysis. The transformation course and characteristic temperatures were determined by the use of differential scanning calorimetry (DSC) and magnetic balance techniques. The results show that Tc of the annealed sample was found to decrease with increasing the annealing temperature. The Ms and Af increases with increasing annealing temperatures and showed best results in 1173K. The studied alloy exhibits a martensitic transformation from a L21 austenite to a martensite phase with a 7-layer (14M) and 5-layer (10M) modulated structure. The lattice constants of the L21 (a0) structure determined by TEM and X-ray analysis in this alloy were a0=0,4866. The TEM observation exhibit that the studied alloy in initial state has bigger accumulations of 10M and 14M structures as opposed from the annealed state.

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.

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