scholarly journals Influence of the transition width on the magnetocaloric effect across the magnetostructural transition of Heusler alloys

2016 ◽  
Vol 374 (2074) ◽  
pp. 20150306 ◽  
Author(s):  
F. Cugini ◽  
G. Porcari ◽  
S. Fabbrici ◽  
F. Albertini ◽  
M. Solzi
Keyword(s):  
Magnetocaloric Effect ◽  
Heusler Alloys ◽  
Entropy Change ◽  
Large Temperature ◽  
Transition Width ◽  
Critical Temperatures ◽  
Magnetostructural Transition ◽  
Magnetocaloric Properties ◽  
Clear Result ◽  
Effective Use

We report a complete structural and magneto-thermodynamic characterization of four samples of the Heusler alloy Ni-Co-Mn-Ga-In, characterized by similar compositions, critical temperatures and high inverse magnetocaloric effect across their metamagnetic transformation, but different transition widths. The object of this study is precisely the sharpness of the martensitic transformation, which plays a key role in the effective use of materials and which has its origin in both intrinsic and extrinsic effects. The influence of the transition width on the magnetocaloric properties has been evaluated by exploiting a phenomenological model of the transformation built through geometrical considerations on the entropy versus temperature curves. A clear result is that a large temperature span of the transformation is unfavourable to the magnetocaloric performance of a material, reducing both isothermal entropy change and adiabatic temperature change obtainable in a given magnetic field and increasing the value of the maximum field needed to fully induce the transformation. The model, which is based on standard magnetometric and conventional calorimetric measurements, turns out to be a convenient tool for the determination of the optimum values of transformation temperature span in a trade-off between sheer performance and amplitude of the operating range of a material. This article is part of the themed issue ‘Taking the temperature of phase transitions in cool materials’.

Magnetocaloric Properties and Magnetic Anisotropy by Tailoring Phase Transitions in NiMnGa Alloys

2008 ◽  
Vol 583 ◽  
pp. 169-196 ◽  
Author(s):  
Franca Albertini ◽  
Massimo Solzi ◽  
Antonio Paoluzi ◽  
Lara Righi
Keyword(s):  
Magnetic Anisotropy ◽  
Magnetocaloric Effect ◽  
Magnetic Transition ◽  
Critical Temperatures ◽  
First Order ◽  
Magnetostructural Transition ◽  
Thermomagnetic Analysis ◽  
Magnetocaloric Properties ◽  
Giant Magnetocaloric Effect ◽  
Composition Changes

The giant magnetocaloric properties of NiMnGa alloys can be enhanced by suitable composition changes that make structural and magnetic transition temperatures to coincide. In this paper we report results on critical temperatures, magnetic anisotropy, and magnetocaloric effect in Ni- and Mn-rich alloys as a function of composition. A phenomenological phase diagram, useful for the identification by thermomagnetic analysis of magnetic and structural transitions in the vicinity of their coincidence, is proposed. Particular emphasis is given to the discussion of giant magnetocaloric effect of those alloys showing a first order magnetostructural transition, the method of its determination, and the potentialities for applications in the field of magnetic refrigeration.

scholarly journals Magnetic Properties and Magnetocaloric Effect in Gd100-xCox Thin Films

Crystals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 278 ◽  
Author(s):  
Mohamed Tadout ◽  
Charles-Henri Lambert ◽  
Mohammed El Hadri ◽  
Abdelilah Benyoussef ◽  
Mohammed Hamedoun ◽  
...  
Keyword(s):  
Thin Films ◽  
Magnetocaloric Effect ◽  
Magnetic Entropy Change ◽  
Entropy Change ◽  
Magnetic Thin Films ◽  
Critical Parameters ◽  
Cooling Power ◽  
Magnetocaloric Properties ◽  
Co Concentration ◽  
Key Parameter

We investigated the magnetic and magnetocaloric properties of Gd100-xCox ( x = 40 to 56) thin films fabricated by the sputtering technique. Under an applied field change Δ H = 20 kOe , the magnetic entropy change ( Δ S m ) decreases from 2.64 Jkg−1K−1 for x = 44 to about 1.27 Jkg−1K−1 for x = 56. Increasing the Co concentration from x = 40 to 56 shifts the Curie temperature of Gd100-xCox ( x = 40 to 56) thin films from 180 K toward 337 K. Moreover, we extracted the values of critical parameters Tc, β, γ, and δ by using the modified Arrott plot methods. The results indicate the presence of a long-range ferromagnetic order. More importantly, we showed that the relative cooling power (RCP), which is a key parameter in magnetic refrigeration applications, is strongly enhanced by changing the Co concentration in the Gd100-xCox thin films. Our findings help pave the way toward the enhancement of the magnetocaloric effect in magnetic thin films.

Experimental Study of Magnetocaloric Effect in Ni-Fe-Mn-Ga and Ni-Co-Mn-Ga Heusler Alloys

2013 ◽  
Vol 738-739 ◽  
pp. 456-460 ◽  
Author(s):  
Rafael Fayzullin ◽  
Vasiliy D. Buchelnikov ◽  
Sergey Taskaev ◽  
Mikhail Drobosyuk ◽  
Vladimir V. Khovaylo
Keyword(s):  
Martensitic Transformation ◽  
Curie Temperature ◽  
Magnetocaloric Effect ◽  
Temperature Increase ◽  
Direct Method ◽  
Heusler Alloys ◽  
Iron Concentration ◽  
Magnetostructural Transition ◽  
Phase Transition Temperatures ◽  
Magnetic Field Change

In this work we experimentally studied the MCE in the Heusler alloys Ni2.19-xFexMn0.81Ga (x = 0.01, 0.02, 0.03, 0.04) and Ni2.16-xCoxMn0.84Ga (x = 0.03, 0.06, 0.09). Magnetocaloric effect was measured by the direct method using the installation from the company AMT&C. The temperature dependencies of ∆Tad for the magnetic field change ∆H = 2 T were measured. The phase transition temperatures were determined from temperature dependencies of low field magnetization measured by original setup using Hall effect. Studies have shown that replacement of the Ni atoms with the iron atoms slightly reduces the temperature magnetostructural transition for x = 0.01,0.02, and starting with x = 0.03, magnetic and structural transitions occur separately and a further increase in iron concentration leads to the Curie temperature increase, while the temperature martensitic transformation decreases. When replacing the Ni atoms with the Co atoms of the martensitic transformation temperature and Curie temperature increase.

Thermomagnetic Properties and Magnetocaloric Effect of R2Fe17C (R=Dy, Nd, Tb, Gd, Pr, Ho, Er) Compounds

2018 ◽  
Vol 1 (1) ◽  
pp. 268-278
Author(s):  
Ahmed Nagy ◽  
Samy H. Aly ◽  
Sherif Yehia ◽  
Tareq Hammad
Keyword(s):  
Magnetocaloric Effect ◽  
Mean Field ◽  
Entropy Change ◽  
Field Analysis ◽  
Magnetic Phase Transitions ◽  
Mean Field Model ◽  
Magnetocaloric Properties ◽  
The Mean ◽  
Thermomagnetic Properties ◽  
Critical Temperature Tc

We present a mean-field analysis, using the two-sublattice model, for the thermomagnetic and magnetocaloric properties of the R2Fe17C compounds, where R=Dy, Nd, Tb, Gd, Pr, Ho, Er and C is carbon.   The dependence of magnetization, magnetic heat capacity, magnetic entropy and isothermal entropy change ∆Sm, are calculated for magnetic fields up to 5T and for temperatures up to 700 K . Direct magnetocaloric effect is present for all compounds with maximum ∆Sm between 6.13-10.95 J/K. mole for an applied field change of 5T. It is found that Pr2Fe17C compound has the highest  ∆Sm of 10.95 J/K. mole at ∆H=5T and Tc=375 K. The inverse MCE is found in ferrimagnetic compounds, e.g. Gd2Fe17C, with ∆Sm= J/K mol at critical temperature Tc=623K and ∆Sm=  J/K mol at Neel temperature TN=136 K.  The calculated Arrott plots confirmed that the magnetic phase transitions in these compounds are of second order. The mean-field model proves its suitability for calculating the properties of the compounds under study.

Magnetocaloric Properties of Cold Rolled Gd100-xZrx (x = 0, 1, 2, 3) Intermetallic Alloys

2015 ◽  
Vol 233-234 ◽  
pp. 220-224 ◽  
Author(s):  
Sergey Taskaev ◽  
Konstantin Skokov ◽  
Dmitriy Karpenkov ◽  
Vladimir V. Khovaylo ◽  
Vasiliy D. Buchelnikov ◽  
...  
Keyword(s):  
Magnetocaloric Effect ◽  
Heat Exchangers ◽  
Large Temperature ◽  
Intermetallic Alloys ◽  
Magnetic Cooling ◽  
Magnetocaloric Properties ◽  
Cooling Devices ◽  
Cold Rolled ◽  
Magnetocaloric Materials ◽  
Large Temperature Interval

In this work we report the results of experimental investigation of the magnetocaloric effect in Gd100-xZrx(x= 0, 1, 2, 3) cold rolled ribbons. As it is shown the magnetocaloric effect exist within the large temperature interval 279-295 K and comparable with magnetocaloric effect observed on pure Gd. As it shown cold rolling is one of promising techniques for producing thin forms of magnetocaloric materials for heat exchangers of magnetic cooling devices.

The Magnetocaloric Effect and Magnetic Transitions in Hydride Compounds: GdNiH3.2 and TbNiH3.4

2015 ◽  
Vol 233-234 ◽  
pp. 243-246
Author(s):  
A.I. Smarzhevskaya ◽  
S.A. Nikitin ◽  
Viktor N. Verbetsky ◽  
Wacław Iwasieczko ◽  
Alexey N. Golovanov
Keyword(s):  
Magnetocaloric Effect ◽  
Magnetic Entropy Change ◽  
Entropy Change ◽  
Magnetic Entropy ◽  
Magnetic Transitions ◽  
Isothermal Magnetization ◽  
Magnetocaloric Properties ◽  
Magnetization Data

The paper presents the investigation of GdNiH3.2 and TbNiH3.4 hydrides magnetic transitions and magnetocaloric properties. The isothermal magnetization data in the fields up to 5T are obtained for GdNi and TbNi compounds and their hydrides and the values of magnetic entropy change are calculated. The maximum values of magnetic entropy change ΔSM in GdNiH3.2 and TbNiH3.4 are extremely large. It is shown that the hydrogenation shifts ΔSM(T) maximum to lower temperatures.

MAGNETIC ENTROPY CHANGE IN A TWO-DIMENSIONAL ANTIFERROMAGNETIC SQUARE LATTICE

2006 ◽  
Vol 20 (18) ◽  
pp. 2527-2536
Author(s):  
H. GENCER
Keyword(s):  
Magnetocaloric Effect ◽  
Magnetic Entropy Change ◽  
Nearest Neighbor ◽  
Entropy Change ◽  
Square Lattice ◽  
Magnetic Entropy ◽  
Maximum Value ◽  
Magnetocaloric Properties ◽  
State Present ◽  
Entropy Variation

In this study, we investigate magnetic entropy variation and magnetocaloric properties as a function of frustration by considering a spin-1/2 antiferromagnetic Heisenberg model on a square lattice with nearest (J1) and next-nearest neighbor exchange interaction (J2). We show that the degree of frustration in the square lattice increases with α=J2/J1. While the square lattice is unfrustrated for α = 0, it becomes fully frustrated for α=0.5. Numerical results show that the entropy of the square lattice approaches zero for the unfrustrated case at T=1 K. In contrast, finite entropy can survive in the frustrated case at the same temperature. We also calculate the magnetic entropy change (ΔSm) in the square lattice and show that the maximum value of ΔSm increases with increasing α. These results indicate that the magnetic entropy change and consequently the magnetocaloric effect can be enhanced by increasing the degree of frustration. We conclude that the enhanced magnetocaloric effect is related to quantum fluctuations and disordered ground state present in the frustrated square lattice.

Realization of Magnetostructural Transition and Magnetocaloric Properties of Ni–Mn–Mo–Sn Heusler Alloys

2018 ◽  
Vol 32 (3) ◽  
pp. 659-665
Author(s):  
Ishfaq Ahmad Shah ◽  
Najam ul Hassan ◽  
Abudu keremu ◽  
Saira Riaz ◽  
Shahzad Naseem ◽  
...  
Keyword(s):  
Heusler Alloys ◽  
Magnetostructural Transition ◽  
Magnetocaloric Properties

Study of Magnetocaloric Properties of Ni-Mn-X (X = Ga, In) Heusler Alloys by Monte Carlo Technique

2009 ◽  
Vol 1200 ◽  
Author(s):  
Vasiliy Buchelnikov ◽  
Vladimir Sokolovskiy ◽  
Sergey Taskaev ◽  
Peter Entel
Keyword(s):  
Experimental Data ◽  
Phase Transition ◽  
Monte Carlo ◽  
Magnetic Entropy Change ◽  
Heusler Alloys ◽  
Entropy Change ◽  
Magnetic Contribution ◽  
Magnetic Entropy ◽  
First Order ◽  
Magnetocaloric Properties

AbstractTwo theoretical Monte Carlo models have been presented for description of the positive and negative magnetocaloric effects of Heusler Ni-Mn-X (X = Ga, In) alloys undergoing first order coupled magnetostructural phase transition. For both models all quantities such as temperature dependence of the magnetic contribution to the total specific heat, magnetization and isothermal magnetic entropy change are in qualitative agreement with the available experimental data.

scholarly journals Magnetocaloric Effect in Cu5-NIPA Molecular Magnet: A Theoretical Study

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 485 ◽  
Author(s):  
Karol Szałowski ◽  
Pamela Kowalewska
Keyword(s):  
Magnetic Field ◽  
Magnetocaloric Effect ◽  
Theoretical Study ◽  
Canonical Ensemble ◽  
Entropy Change ◽  
Molecular Magnet ◽  
Wide Range ◽  
Magnetocaloric Properties ◽  
Magnetic Specific Heat ◽  
High Degree

We calculated the magnetocaloric properties of the molecular nanomagnet Cu5-NIPA, consisting of five spins S = 1 / 2 arranged in two corner-sharing triangles (hourglass-like structure without magnetic frustration). The thermodynamics of the system in question was described using the quantum Heisenberg model solved within the field ensemble (canonical ensemble) using exact numerical diagonalization. The dependence of the magnetic entropy and magnetic specific heat on the temperature and the external magnetic field was investigated. The isothermal entropy change for a wide range of initial and final magnetic fields was discussed. Due to plateau-like behavior of the isothermal entropy change as a function of the temperature, a high degree of tunability of magnetocaloric effect with the initial and final magnetic field was demonstrated.

Sign in / Sign up

Export Citation Format

Share Document