scholarly journals Low-Temperature Magnetocaloric Properties of V12 Polyoxovanadate Molecular Magnet: A Theoretical Study

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4399 ◽  
Author(s):  
Karol Szałowski
Keyword(s):  
Low Temperature ◽  
Magnetocaloric Effect ◽  
Computational Study ◽  
Thermodynamic Description ◽  
Entropy Change ◽  
Molecular Magnet ◽  
Thermodynamic Quantities ◽  
Magnetocaloric Properties ◽  
Adiabatic Magnetization ◽  
Quantities Of Interest

The paper presents a computational study of the magnetocaloric properties of the V12 polyoxovanadate molecular magnet. The description is restricted to low-temperature range (below approximately 100 K), where the magnetic properties of the system in question can be sufficiently modelled by considering a tetramer that consists of four vanadium ions with spins S=1/2. The discussion is focused on the magnetocaloric effect in the cryogenic range. The exact and numerical diagonalization of the corresponding Hamiltonian is used in order to construct the thermodynamic description within a version of the canonical ensemble. The thermodynamic quantities of interest, such as magnetic entropy, specific heat, entropy change under isothermal magnetization/demagnetization, temperature change under adiabatic magnetization/demagnetization, refrigerant capacity, and magnetic Grüneisen ratio, are calculated and discussed extensively. The importance of two quantum level crossings for the described properties is emphasized. The significant ranges of direct and inverse magnetocaloric effect are predicted. In particular, the maximized inverse magnetocaloric response is found for cryogenic temperatures.

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.

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 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.

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.

scholarly journals Gaudefroyite: a mineral with excellent magnetocaloric effect suitable for liquefying hydrogen

2018 ◽  
Vol 6 (13) ◽  
pp. 5260-5264 ◽  
Author(s):  
Rukang Li ◽  
Guangjing Li ◽  
Colin Greaves
Keyword(s):  
Low Temperature ◽  
Magnetocaloric Effect ◽  
Natural Mineral ◽  
Magnetocaloric Properties

A natural mineral, gaudefroyite, displays excellent low temperature magnetocaloric properties that are suitable for liquefying hydrogen.

Giant low-field reversible magnetocaloric effect in HoCoGe compound

RSC Advances ◽  
2016 ◽  
Vol 6 (108) ◽  
pp. 106171-106176 ◽  
Author(s):  
Y. Zhang ◽  
Q. Y. Dong ◽  
L. C. Wang ◽  
M. Zhang ◽  
H. T. Yan ◽  
...  
Keyword(s):  
Low Temperature ◽  
Magnetocaloric Effect ◽  
Temperature Change ◽  
Magnetic Entropy Change ◽  
Entropy Change ◽  
Magnetic Entropy ◽  
Temperature Range ◽  
Low Field ◽  
Adiabatic Temperature Change ◽  
Attractive Candidate

HoCoGe compound shows large magnetic entropy change and adiabatic temperature change, which makes it an attractive candidate for magnetic refrigeration in the low temperature range.

Multiple magnetic transitions and magnetocaloric effect in hydrothermally synthesized single crystalline La0.5Sr0.5MnO3nanowires

2012 ◽  
Vol 1454 ◽  
pp. 63-68 ◽  
Author(s):  
Sayan Chandra ◽  
Anis Biswas ◽  
Subarna Datta ◽  
Barnali Ghosh ◽  
A.K. Raychaudhuri ◽  
...  
Keyword(s):  
Hydrothermal Synthesis ◽  
Low Temperature ◽  
Magnetocaloric Effect ◽  
Room Temperature ◽  
Magnetic State ◽  
Double Exchange ◽  
Synthesis Process ◽  
Theoretical Studies ◽  
Magnetic Transitions ◽  
Magnetocaloric Properties

ABSTRACTWe have successfully prepared La0.5Sr0.5MnO3nanowires using a novel hydrothermal synthesis process and studied their magnetic and magnetocaloric properties. The system exhibits an inverse magnetocaloric effect (IMCE) around 175 K indicating presence of significant AFM correlation. The MCE study reveals a clear paramagnetic (PM) to ferromagnetic (FM) transition near room temperature (T ~ 325K) which is followed by onset of AFM at lower temperatures. The development of the FM-like magnetic state at low temperature is attributed to the enhanced double exchange (DE) driven ferromagnetism in AFM state as predicted by recent theoretical studies.

Magnetic and magnetocaloric properties of Dy5Pd2: role of magnetic irreversibility

RSC Advances ◽  
2015 ◽  
Vol 5 (59) ◽  
pp. 47860-47865 ◽  
Author(s):  
Tapas Paramanik ◽  
Tapas Samanta ◽  
R. Ranganathan ◽  
I. Das
Keyword(s):  
Intermetallic Compound ◽  
Low Temperature ◽  
Magnetocaloric Effect ◽  
Temperature Region ◽  
Magnetocaloric Properties ◽  
Magnetic Irreversibility

In this report the origin of giant inverse magnetocaloric effect at low temperature region has been studied in cluster glass intermetallic compound Dy5Pd2. In this context the procedure to obtain reversible magnetocaloric effect using Maxwell’s relation has been described.

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.

Sign in / Sign up

Export Citation Format

Share Document