Tailoring of Magnetocaloric Effect in Ni45.5Mn43.0In11.5 Metamagnetic Shape Memory Alloy

We investigate the direct and inverse magnetocaloric effect in Ni45.5Mn43.0In11.5 Heusler alloy ribbons comparing the results obtained for the as-quenched sample with the ones after different annealing procedures. An enhancement and shift of the entropy maximum to near room temperature is observed in all annealed samples. A remarkable magnetocaloric effect is observed in samples with short-time treatment (10 minutes) and at the lowest annealing temperature. We show that the suppressing of uncompensated martensitic transition and thermal hysteresis are both influenced by the heat treatment. Also, an improvement on Curie’s temperature is observed and, at low magnetic field, it has been risen up to 310 K. Our results demonstrate that the martensitic transformation is highly sensitive to the applied magnetic field and also to the annealing treatment, which means that the magnetocaloric effect can be tuned showing different behaviors for each sample.

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Effect of changing P/Ge and Mn/Fe ratios on the magnetocaloric effect and structural transition in the (Mn,Fe)2 (P,Ge) intermetallic compounds

Materials Science-Poland ◽

10.1515/msp-2016-0068 ◽

2016 ◽

Vol 34 (3) ◽

pp. 494-502 ◽

Cited By ~ 1

Author(s):

P. Wlodarczyk ◽

L. Hawelek ◽

P. Zackiewicz ◽

M. Kaminska ◽

A. Chrobak ◽

...

Keyword(s):

Magnetic Field ◽

Curie Temperature ◽

Magnetocaloric Effect ◽

Intermetallic Compounds ◽

Structural Transition ◽

Thermal Hysteresis ◽

Simultaneous Increase ◽

Low Field ◽

Transition Enthalpy ◽

Low Magnetic Field

AbstractThe magnetocaloric effect in the MnxFe2−xP1−yGey intermetallic compounds with the amount of Mn in the range of x = 1.05 to 1.17 and amount of Ge in the range of y = 0.19 to 0.22 has been studied. It was found that a higher Ge/P ratio causes an increase in Curie temperature, magnetocaloric effect at low field (up to 1 T), activation energy of structural transition and a decrease in thermal hysteresis, as well as transition enthalpy. Contrary to this observation, higher Mn/Fe ratio causes a decrease in Curie temperature, slight decrease of magnetocaloric effect at low magnetic field, and an increase in thermal hysteresis. Simultaneous increase of both ratios may be very advantageous, as the thermal hysteresis can be lowered and magnetocaloric effect can be enhanced without changing the Curie temperature. Some hints about optimization of the composition for applications at low magnetic fields (0.5 T to 2 T) have been presented.

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Stretching of the Super-Elastic Double-Helix Geon. Wheeler´s Thermal Geons as Quanta of Heat and Momentum. Bohm´s Diffusion and the Heating of the Solar Corona and Heating of the Earth - Geon Engineering. Milgrom-Verlinde Constant. Mareš - Šesták constant

Applied Physics Research ◽

10.5539/apr.v12n2p12 ◽

2020 ◽

Vol 12 (2) ◽

pp. 12

Author(s):

Jiri Stavek

Keyword(s):

Magnetic Field ◽

Field Strength ◽

Solar Corona ◽

Magnetic Field Strength ◽

Double Helix ◽

David Bohm ◽

The Earth ◽

Highly Sensitive ◽

Low Magnetic Field ◽

The Magnetic Field

In our approach we have combined knowledge of Old Masters (working in this field before the year 1905), New Masters (working in this field after the year 1905) and Dissidents under the guidance of Louis de Broglie and David Bohm. Based on the great works of Julian Schwinger and John Archibald Wheeler we will study properties of geons formed by fusion of two soft x-ray particles (dyons) in the Schwarzschild gravitation core in our Sun at temperature 16 * 106 K. There are now several Teams that are able to achieve this fusion temperature in their special instruments (Tokamak, HL-2M Tokamak, Wendelstein 7-X, NIF, etc.) and to study properties of those formed geons. Thermal geons are with us all the time but they are very deeply hidden in our experiments. We have newly introduced Mareš - Šesták constant as the ratio of geon momentum to heat quantum of geon. The key information to enter into the World of geons was the empirical formula of David Bohm - the very well-known Bohm diffusion. From this formula we have extracted the amplitude, wavelength, frequency, quantum of the geon action, displacement law for geons, etc. It was found that geons are highly sensitive to the magnetic field strength. At a low magnetic field strength, the “inflation of geons” can occur. This effect could explain the Superheating of the Solar corona and the observed Heating of the Earth during two last centuries influenced by the changes in the Earth´s magnetic field. Geon engineering might modify the geon volume through the magnetic field strength. On the other hand, we were stimulated by the works of Mordehai Milgrom and Eric Verlinde and derived the Milgrom-Verlinde constant describing the gravitational field strength leading to the Newtonian gravitational constant on thermodynamic principles. The quantum of the geon momentum might open a new way how to understand gravitational phenomena. Can it be that Nature cleverly inserted geons into our experimental apparatuses and into our very-well known Old Formulae? We want to pass this concept into the hands of Readers of this Journal better educated in the Mathematics, Physics, and Thermodynamics.

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