scholarly journals Direct and Indirect Determination of the Magnetocaloric Effect in the Heusler Compound Ni1.7Pt0.3MnGa

Entropy ◽  
2021 ◽  
Vol 23 (10) ◽  
pp. 1273
Author(s):  
Ricardo D. dos Reis ◽  
Luana Caron ◽  
Sanjay Singh ◽  
Claudia Felser ◽  
Michael Nicklas
Keyword(s):  
Magnetocaloric Effect ◽  
Direct Methods ◽  
Entropy Change ◽  
Measuring Method ◽  
Martensitic Transition ◽  
Magnetic Shape Memory ◽  
Flow Measurements ◽  
Indirect Determination ◽  
Practical Applications ◽  
First Order

Magnetic shape-memory materials are potential magnetic refrigerants, due the caloric properties of their magnetic-field-induced martensitic transformation. The first-order nature of the martensitic transition may be the origin of hysteresis effects that can hinder practical applications. Moreover, the presence of latent heat in these transitions requires direct methods to measure the entropy and to correctly analyze the magnetocaloric effect. Here, we investigated the magnetocaloric effect in the Heusler material Ni1.7Pt0.3MnGa by combining an indirect approach to determine the entropy change from isofield magnetization curves and direct heat-flow measurements using a Peltier calorimeter. Our results demonstrate that the magnetic entropy change ΔS in the vicinity of the first-order martensitic phase transition depends on the measuring method and is directly connected with the temperature and field history of the experimental processes.

Magnetic Entropy Changes in Ni54.9Mn20.5Ga24.6 Alloy

2005 ◽  
Vol 475-479 ◽  
pp. 2243-2246
Author(s):  
Da Wen ◽  
Ze Yu Zhang ◽  
Yi Long ◽  
Rong Chang Ye ◽  
Zhuhong Liu ◽  
...  
Keyword(s):  
Magnetocaloric Effect ◽  
Magnetic Entropy Change ◽  
Entropy Change ◽  
Martensitic Transition ◽  
Martensitic Structure ◽  
Magnetic Entropy ◽  
Structure Transition ◽  
Martensitic State ◽  
Giant Magnetocaloric Effect ◽  
First Order Phase

Giant magnetocaloric effect based on first order phase transformation has been investigated extensively recently. A considerable magnetic entropy change has been found in single crystal Ni52.6Mn23.1Ga24.3, Ni53Mn22Ga25 and polycrystal Ni51.5Mn22.7Ga25.8.This change originated from a sharp magnetization jump caused by the martensitic-austenitic structure transition on heating. In this paper, magnetocaloric effect in the alloys Ni54.9Mn20.5Ga24.6 is studied. The Curie point temperature Tc of the alloy is adjusted to the vicinity of martensitic transition temperature Tm. The concurrence of martensitic structure transition and magnetic phase transition enhance the magnetocaloric effect in these alloys. The martensitic structure transition effect on the magnetic properties of the alloys is investigated. The character of magnetocaloric effect during the transition from the austenitic to martensitic state is discussed.

scholarly journals Critical dependence of magnetostructural coupling and magnetocaloric effect on particle size in Mn-Fe-Ni-Ge compounds

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Rongrong Wu ◽  
Feiran Shen ◽  
Fengxia Hu ◽  
Jing Wang ◽  
Lifu Bao ◽  
...  
Keyword(s):  
Particle Size ◽  
Magnetocaloric Effect ◽  
Magnetic Transition ◽  
Magnetic Hysteresis ◽  
Negative Thermal Expansion ◽  
Entropy Change ◽  
Cooling Power ◽  
Austenitic Phase ◽  
Magnetic Actuators ◽  
Practical Applications

Abstract Magnetostructural coupling, which is the coincidence of crystallographic and magnetic transition, has obtained intense attention for its abundant magnetoresponse effects and promising technological applications, such as solid-state refrigeration, magnetic actuators and sensors. The hexagonal Ni2In-type compounds have attracted much attraction due to the strong magnetostructural coupling and the resulted giant negative thermal expansion and magnetocaloric effect. However, the as-prepared samples are quite brittle and naturally collapse into powders. Here, we report the effect of particle size on the magnetostructural coupling and magnetocaloric effect in the Ni2In-type Mn-Fe-Ni-Ge compound, which undergoes a large lattice change across the transformation from paramagnetic austenite to ferromagnetic martensite. The disappearance of martensitic transformation in a large amount of austenitic phase with reducing particle size, to our best knowledge, has not been reported up to now. The ratio can be as high as 40.6% when the MnNi0.8Fe0.2Ge bulk was broken into particles in the size range of 5~15 μm. Meanwhile, the remained magnetostructural transition gets wider and the magnetic hysteresis becomes smaller. As a result, the entropy change drops, but the effective cooling power RC effe increases and attains to the maximum at particles in the range of 20~40 μm. These observations provide constructive information and highly benefit practical applications for this class of novel magnetoresponse materials.

Large reversible entropy change at the inverse magnetocaloric effect in Ni-Co-Mn-Ga-In magnetic shape memory alloys

2013 ◽  
Vol 113 (21) ◽  
pp. 213905 ◽  
Author(s):  
Baris Emre ◽  
Süheyla Yüce ◽  
Enric Stern-Taulats ◽  
Antoni Planes ◽  
Simone Fabbrici ◽  
...  
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Magnetocaloric Effect ◽  
Entropy Change ◽  
Magnetic Shape Memory ◽  
Magnetic Shape Memory Alloys

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.

scholarly journals Peculiarities of the magnetocaloric effect in FeRh-based alloys in the vicinity of the first order magnetic phase transition

2018 ◽  
Vol 185 ◽  
pp. 05008 ◽  
Author(s):  
Radel Gimaev ◽  
Vladimir Zverev ◽  
Yury Spichkin ◽  
Alexander Tishin ◽  
Takafumi Miyanaga
Keyword(s):  
Phase Transition ◽  
Magnetocaloric Effect ◽  
Magnetic Phase Transition ◽  
Density Functional ◽  
Magnetic Phase ◽  
Practical Applications ◽  
First Order ◽  
Asymmetric Behaviour ◽  
Giant Magnetocaloric Effect ◽  
Order Magnetic Phase Transition

Medical applications of magnetocaloric effect (MCE) require possibility for precision shift of a temperature of the magnetic phase transition at the same MCE value and minimize irreversibility. Thus, detail dynamic MCE investigation of such alloys with non-toxic biocompatible dopants need to be done. In present work, the giant magnetocaloric effect, which is observed in the whole family of Fe-Rh alloys, has been investigated in Pd-doped samples in slowly cycled magnetic fields of up to 1.8 T in magnitude for a range of temperatures, 250 K < T < 350 K. The shift of the ferromagnetic/antiferromagnetic transition temperature down towards room temperature and the decrease in the MCE have been observed in these alloys in comparison with a quasi-equiatomic FeRh alloy. The measurements have also shown an asymmetric behaviour of the first order magnetic phase transition with respect to whether the transition is traversed by heating from lower temperatures or cooling from above. These peculiarities have been explained in the framework of the ab-initio density functional theory-based disordered local moment theory of the MCE. The results have been compared with the those for the non-doped FeRh alloy. Thus features of the first order magnetic phase transition that these alloys have in common have been revealed which enable some predictions to be made appropriate for practical applications.

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.

Large magnetic entropy change at cryogenic temperature in rare earth HoN nanoparticles

RSC Advances ◽  
2016 ◽  
Vol 6 (79) ◽  
pp. 75562-75569 ◽  
Author(s):  
K. P. Shinde ◽  
S. H. Jang ◽  
M. Ranot ◽  
B. B. Sinha ◽  
J. W. Kim ◽  
...  
Keyword(s):  
Rare Earth ◽  
Low Temperature ◽  
Magnetocaloric Effect ◽  
Cryogenic Temperature ◽  
Magnetic Entropy Change ◽  
Entropy Change ◽  
Environmental Problems ◽  
Magnetic Refrigeration ◽  
Magnetic Entropy ◽  
Alternative Technology

The most extensive cooling techniques based on gases have faced environmental problems. The magnetic refrigeration is an alternative technology based on magnetocaloric effect. HoN nanoparticles are good refrigerant material at low temperature.

scholarly journals Reversibility of the Magnetocaloric Effect in the Bean-Rodbell Model

2021 ◽  
Vol 7 (5) ◽  
pp. 60
Author(s):  
Luis M. Moreno-Ramírez ◽  
Victorino Franco
Keyword(s):  
Magnetic Field ◽  
Thermal Hysteresis ◽  
Entropy Change ◽  
Second Order ◽  
Zero Field ◽  
First Order ◽  
Magnetic Field Change ◽  
Magnetocaloric Materials ◽  
Moderate Magnetic Field ◽  
The Magnetic Field

The applicability of magnetocaloric materials is limited by irreversibility. In this work, we evaluate the reversible magnetocaloric response associated with magnetoelastic transitions in the framework of the Bean-Rodbell model. This model allows the description of both second- and first-order magnetoelastic transitions by the modification of the η parameter (η<1 for second-order and η>1 for first-order ones). The response is quantified via the Temperature-averaged Entropy Change (TEC), which has been shown to be an easy and effective figure of merit for magnetocaloric materials. A strong magnetic field dependence of TEC is found for first-order transitions, having a significant increase when the magnetic field is large enough to overcome the thermal hysteresis of the material observed at zero field. This field value, as well as the magnetic field evolution of the transition temperature, strongly depend on the atomic magnetic moment of the material. For a moderate magnetic field change of 2 T, first-order transitions with η≈1.3−1.8 have better TEC than those corresponding to stronger first-order transitions and even second-order ones.

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