scholarly journals Phase Transitions and Magnetocaloric Properties in MnCo1−xZrxGe Compounds

2017 ◽  
Vol 2017 ◽  
pp. 1-6 ◽  
Author(s):  
Anil Aryal ◽  
Abdiel Quetz ◽  
Sudip Pandey ◽  
Igor Dubenko ◽  
Shane Stadler ◽  
...  
Keyword(s):  
Transition Temperature ◽  
Ferromagnetic State ◽  
Partial Substitution ◽  
Cooling Power ◽  
Martensitic Transition ◽  
Ferromagnetic Transition ◽  
Scanning Calorimetry ◽  
Magnetostructural Transition ◽  
Magnetocaloric Properties ◽  
Single Transition

The structural, magnetic, and magnetocaloric properties of MnCo1-xZrxGe (0.01≤x≤0.04) have been studied through X-ray diffraction, differential scanning calorimetry, and magnetization measurements. Results indicate that the partial substitution of Zr for Co in MnCo1-xZrxGe decreases the martensitic transition temperature (TM). For x = 0.02, TM was found to coincide with the ferromagnetic transition temperature (TC) resulting in a first-order magnetostructural transition (MST). A further increase in zirconium concentration (x = 0.04) showed a single transition at TC. The MST from the paramagnetic to ferromagnetic state results in magnetic entropy changes (-ΔSM) of 7.2 J/kgK for ΔH = 5 T at 274 K for x = 0.02. The corresponding value of the relative cooling power (RCP) was found to be 266 J/kg for ΔH = 5 T. The observed large value of MCE and RCP makes this system a promising material for magnetic cooling applications.

Enhancement of Magnetocaloric Effects in Single Phase La1-zNdz(Fe0.88S 0.12)13

2007 ◽  
Vol 561-565 ◽  
pp. 1093-1096 ◽  
Author(s):  
S. Fujieda ◽  
A. Fujita ◽  
Kazuaki Fukamichi
Keyword(s):  
Single Phase ◽  
Entropy Change ◽  
Ferromagnetic State ◽  
Partial Substitution ◽  
Cooling Power ◽  
Itinerant Electron ◽  
Magnetic Field Change ◽  
First Order Transition ◽  
Cure Temperature ◽  
The Magnetic Field

The single phase of a cubic NaZn13-type La1-zNdz(Fe0.88Si0.12)13 is obtained in the region z ≤ 0.2. The field-induced first-order transition from the paramagnetic to ferromagnetic state, that is, the itinerant-electron metamagnetic (IEM) transition is kept after the substitution of Nd. In addition, a discontinuous change of magnetization at the Cure temperature becomes larger with increasing z. As a result, the isothermal magnetic entropy change and the relative cooling power in the magnetic field change from 0 to 5 T increase to –27 J/kg K and 518 J/kg, respectively, by the partial substitution of z = 0.2.

scholarly journals Martensitic Transformation, Thermal Analysis and Magnetocaloric Properties of Ni-Mn-Sn-Pd Alloys

Processes ◽  
2020 ◽  
Vol 8 (12) ◽  
pp. 1582
Author(s):  
Asma Wederni ◽  
Mihail Ipatov ◽  
Eloi Pineda ◽  
Lluisa Escoda ◽  
Julian-Maria González ◽  
...  
Keyword(s):  
Structural Transition ◽  
Magnetic Measurements ◽  
Heusler Alloys ◽  
Martensitic Transition ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Enthalpy Changes ◽  
Magnetocaloric Properties ◽  
Pd Doping ◽  
Peak Value

Martensitic transition and magnetic response of Ni50−x Pdx,y Mn36 Sn14−y (x = 0, 1, 2 and y = 0, 1) Heusler alloys were analysed. The crystalline structure of each composition was solved by X-ray diffraction pattern fitting. For x = 1 and 2, the L21 austenite structure is formed and, for y = 1, the crystallographic phase is a modulated martensitic structure. From differential scanning calorimetry scans, we determine characteristic transformation temperatures and the entropy/enthalpy changes. The temperatures of the structural transformation increase with the addition of Pd to replace Ni or Sn, whereas the austenitic Curie temperature remains almost unvarying. In addition, the magneto-structural transition, investigated by magnetic measurements, is adjusted by suitable Pd doping in the alloys. The peak value of the magnetic entropy changes reached 4.5 J/(kg K) for Ni50Mn36Sn13Pd1 (external field: 50 kOe).

scholarly journals Structural, Thermal and Magnetic Properties of Ga Excess Ni-Mn-Ga

2009 ◽  
Vol 635 ◽  
pp. 43-47 ◽  
Author(s):  
Sanjay Singh ◽  
S. Bhardwaj ◽  
A.K. Panda ◽  
V.K. Ahire ◽  
Amitava Mitra ◽  
...  
Keyword(s):  
Differential Scanning Calorimetry ◽  
Magnetic Properties ◽  
Transition Temperature ◽  
Martensitic Transition ◽  
Martensitic Structure ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Ga Doping ◽  
Heat Of Transformation

The martensitic transition and the ferro- to paramagnetic transition have been studied in a series of Ga excess Ni-Mn-Ga specimens [Ni2-xMnGa1+x (0.4≤ x≤ 0.9)] by differential scanning calorimetry and magnetization measurements. The martensitic transition exhibits a hysteresis whose width is similar to Ni2MnGa, indicating that the transition is thermoelastic. The latent heat of transformation is comparable with other Ni-Mn-Ga alloys. A substantial increase in the martensitic transition temperature is observed due to Ga doping. Interestingly, the x-ray diffraction pattern of all the compositions studied show a modulated martensitic structure in the martensitic phase.

scholarly journals Full Variation of Site Substitution in Ni-Mn-Ga by Ferromagnetic Transition Metals

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 850
Author(s):  
Vít Kopecký ◽  
Michal Rameš ◽  
Petr Veřtát ◽  
Ross H. Colman ◽  
Oleg Heczko
Keyword(s):  
Transition Temperature ◽  
Martensitic Transformation ◽  
Curie Temperature ◽  
Transformation Temperature ◽  
Bulk Material ◽  
Martensitic Transition ◽  
Ferromagnetic Transition ◽  
Transition Elements ◽  
Martensitic Transformation Temperature ◽  
Valence Electrons

Systematic doping by transition elements Fe, Co and Ni on each site of Ni2MnGa alloy reveal that in bulk material the increase in martensitic transformation temperature is usually accompanied by the decrease in ferromagnetic Curie temperature, and vice versa. The highest martensitic transformation temperature (571 K) was found for Ni50.0Mn25.4(Ga20.3Ni4.3) with the result of a reduction in Curie temperature by 55 K. The highest Curie point (444 K) was found in alloy (Ni44.9Co5.1)Mn25.1Ga24.9; however, the transition temperature was reduced to 77 K. The dependence of transition temperature is better scaled with the Ne/a parameter (number of non-bonding electrons per atom) compared to usual e/a (valence electrons per atom). Ne/a dependence predicts a disappearance of martensitic transformation in (Ni45.3Fe5.3)Mn23.8Ga25.6, in agreement with our experiment. Although Curie temperature usually slightly decreases while the martensitic transition increases, there is no significant correlation of Curie temperature with e/a or Ne/a parameters. The doping effect of the same element is different for each compositional site. The cascade substitution is discussed and related to the experimental data.

Martensite-austenite and Ferromagnetic-paramagnetic Transformations in Ni2-xAxMn1-yByGa1-zCz (A, B=Co; C=Al) Heusler Alloys

2009 ◽  
Vol 59 (12) ◽  
Author(s):  
Mihail-Liviu Craus ◽  
Viorel Dobrea ◽  
Mihai Lozovan
Keyword(s):  
Magnetic Field ◽  
Transition Temperature ◽  
Martensitic Transformation ◽  
Low Temperatures ◽  
Room Temperature ◽  
Heusler Alloys ◽  
Partial Substitution ◽  
Martensitic Transition ◽  
Cscl Type ◽  
Curie Temperatures

Ni2MnGa Heusler alloy is known as a potential smart material. At room temperature it has a L21 type structure, undergoing a martensitic transition (TM) at low temperatures. Some authors have classified Ni-Mn-Ga Heusler alloys on the values of martensitic transformation and Curie temperatures: first group formed by alloys with TM below room temperature and TC, second group with TM around room temperature and third group with TM]TC. The partial substitution of Ni with Mn leads to an increase of the transition temperature and a decrease of the Curie temperature. The Ni2-xMn1+xGa alloys have a complex tetragonal structure at room temperature. The substitution of Ga with Al can change the crystalline and magnetic structure of Heusler alloys: Ni2MnAl is antiferromagnetic for a B2 (CsCl type, with Mn and Al randomly distributed in the center of the cube) structure and ferromagnetic for a L21 (BiF3 type with Mn and Al ordered distributed in the cube center) structure. We intend to put in evidence a dependence between the applied magnetic field on a side, and the transition temperature, on other side, for the Ni2-xAxMn1-yByGa1-zCz (A, B=Co; C=Al) Heusler alloys.

scholarly journals Thermal analysis: basic concept of differential scanning calorimetry and thermogravimetry for beginners

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Nurul Fatahah Asyqin Zainal ◽  
Jean Marc Saiter ◽  
Suhaila Idayu Abdul Halim ◽  
Romain Lucas ◽  
Chin Han Chan
Keyword(s):  
Thermal Analysis ◽  
Differential Scanning Calorimetry ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Commercial Application ◽  
Scanning Calorimetry ◽  
Teaching Activities ◽  
Sample Decomposition ◽  
Calibration Baseline

AbstractWe present an overview for the basic fundamental of thermal analysis, which is applicable for educational purposes, especially for lecturers at the universities, who may refer to the articles as the references to “teach” or to “lecture” to final year project students or young researchers who are working on their postgraduate projects. Description of basic instrumentation [i.e. differential scanning calorimetry (DSC) and thermogravimetry (TGA)] covers from what we should know about the instrument, calibration, baseline and samples’ signal. We also provide the step-by-step guides for the estimation of the glass transition temperature after DSC as well as examples and exercises are included, which are applicable for teaching activities. Glass transition temperature is an important property for commercial application of a polymeric material, e.g. packaging, automotive, etc. TGA is also highlighted where the analysis gives important thermal degradation information of a material to avoid sample decomposition during the DSC measurement. The step-by-step guides of the estimation of the activation energy after TGA based on Hoffman’s Arrhenius-like relationship are also provided.

scholarly journals Physical Aging Behavior of a Glassy Polyether

Polymers ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 954
Author(s):  
Xavier Monnier ◽  
Sara Marina ◽  
Xabier Lopez de Pariza ◽  
Haritz Sardón ◽  
Jaime Martin ◽  
...  
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Physical Aging ◽  
Glassy State ◽  
Aging Behavior ◽  
Scanning Calorimetry ◽  
Narrow Temperature Range ◽  
Glass Forming ◽  
Fast Scanning Calorimetry

The present work aims to provide insights on recent findings indicating the presence of multiple equilibration mechanisms in physical aging of glasses. To this aim, we have investigated a glass forming polyether, poly(1-4 cyclohexane di-methanol) (PCDM), by following the evolution of the enthalpic state during physical aging by fast scanning calorimetry (FSC). The main results of our study indicate that physical aging persists at temperatures way below the glass transition temperature and, in a narrow temperature range, is characterized by a two steps evolution of the enthalpic state. Altogether, our results indicate that the simple old-standing view of physical aging as triggered by the α relaxation does not hold true when aging is carried out deep in the glassy state.

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