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We report on the giant barocaloric effect and refrigerant capacity in the [Fe(pzt) 6 ](PF 6 ) 2 (pzt = 1-propyltetrazole) spin-crossover material. The refrigerant capacity in [Fe(pzt) 6 ](PF 6 ) 2 is RC = 1380 J kg −1 , 5 times higher than the big value reported in (NH 4 ) 2 SO 4 , upon pressure variation ΔP = 1 kbar. This huge caloric effect is ascribed to the coupling interactions between the crystal lattice (phonons) and the order parameter (γ HS ) that describes the molar fraction of high spin molecules (Fe +2 N 6 )-( t 2 g 4 e g 2 ) in [Fe(pzt) 6 ](PF 6 ) 2 . Our theoretical entropy includes the lattice, electronic and configurational coupled-contributions and was obtained from a microscopic model. A new methodology to obtain the barocaloric effect potentials is presented using a proper thermodynamic Maxwell relation for spin-crossover systems. The experimental results, for the isothermal entropy change, were calculated from the pressure dependence of γ HS data. Besides, the determination of molecular volume change between high and low spin states through caloric measurements was discussed. [ABSTRACT FROM AUTHOR]

• Rotating magnetocaloric effect in ferromagnetic PrRu 2 compound. • Crystalline electrical field anisotropy in cubic Pr3+ compound. • Magnetocaloric effect around spin reorientation phase transition. • Influence of spin reorientation on the magnetocaloric effect. The magnetic anisotropy in the cubic ferromagnetic PrRu 2 compound (T C = 34 K) is due to the crystalline electrical field interaction. Using a model Hamiltonian which includes the crystalline electrical field, exchange and Zeeman interactions we calculated the rotating magnetocaloric effect, considering the magnetic field changes along the three main cubic crystallographic directions 〈0 0 1〉, 〈0 1 1〉 and 〈1 1 1〉. The influence of the spin reorientation, along the field directions, on the magnetocaloric potentials were quantitatively obtained and discussed. [ABSTRACT FROM AUTHOR]

• Barocaloric effect in spin-crossover materials (SCO). • Magnetic, vibrational and configurational entropies contributions at low–high spin phase transition. • Conditions for the appearance of hysteresis in (SCO)-compounds. • Obtention of molecular volume changing, in (SCO)-materials, through the barocaloric effect. We report a theoretical investigation of the entropic barocaloric effect in a spin crossover system. From our model Hamiltonian, the total entropy, which includes the contributions from the lattice (vibrational), magnetic and configurational entropies, was obtained and worked out for a systematic study of the barocaloric effect. The barocaloric effect was parametrically investigated in three scenarios: second order, threshold of second-first order and first order phase transition. Besides, a procedure for obtaining the molecular volume change during the low spin to high spin phase transition conversion was proposed, through the entropic barocaloric measurements. [ABSTRACT FROM AUTHOR]

Abstract: In this work, we use the Monte Carlo method to calculate the magnetocaloric effect in compound, which has second order ferro-paramagnetic phase transition near room temperature. The theoretically calculated isothermal entropy change and the adiabatic temperature change upon magnetic field variations are in good agreement with the available experimental data. [Copyright &y& Elsevier]

A critical need to accurately model thermal behaviors of materials that exhibit strong elastocaloric effects, including predicting the effects themselves at varying stresses and temperatures, has been addressed using a simple and versatile physics-based approach. The key factor leading to the high precision is approximating the underlying elastic phase transition as a smooth modification of lattice entropy between coexisting phases. Once the phase transformation entropy is modeled to match experimentally measured strain as a function of temperature and applied stress, estimating the heat capacity, entropy, and isothermal entropy and adiabatic temperature changes in temperature-stress coordinates becomes straightforward. This approach provides insight into how thermal properties of elastocaloric materials vary through the transition based on strain measurements that are simple to perform and interpret. In addition to aiding in the rapid evaluation of new and existing elastocaloric materials, this advance is expected to prove invaluable for accurate heat transfer modeling aimed at designing efficient regenerative elastocaloric cooling devices. [Display omitted] [ABSTRACT FROM AUTHOR]

• First order antiferromagnetic phase transition in CeMg. • Cubic-tetragonal coupled magnetic phase transition in CeMg. • Normal and inverse magnetocaloric effect in an antiferromagnetic system. • Influence of magnetic anisotropy on the magnetocaloric effect. We report the magnetic and magnetocaloric properties of the antiferromagnetic intermetallic compound CeMg, focusing on its coupled magnetic and structural phase transition within first-order processes. Our study utilizes a model Hamiltonian incorporating interactions such as: crystalline electrical field, intra and inter sublattice exchange interactions, as well as quadrupolar and magnetoelastic to elucidate the behavior of CeMg. Through simulation, we predict and discuss both normal and inverse magnetocaloric effects, providing insights into the magnetocaloric behavior under different magnetic field directions. These findings contribute to a deeper understanding of the complex magnetism in CeMg and lay the groundwork for future experimental investigations. [ABSTRACT FROM AUTHOR]

Abstract: We investigated the inverse magnetocaloric effect using a theoretical magnetic model formed by two coupled magnetic lattices to describe a ferrimagnetic system. The influence of the compensation temperature, and the ferrimagnetic–paramagnetic phase transition on the magnetocaloric effect was analyzed. Also, a relation between the area under the magnetocaloric curve and the net magnetic moment of a ferrimagnetic system was established in this work. [Copyright &y& Elsevier]

• Huge refrigerant capacity in Fe(phen) 2 (NCS) 2. • Barocaloric effect in spin crossover materials. • Entropic caloric effect triggered from (LS)-(HS) phase transition. • Solid refrigerant materials. The next-generation of refrigerant materials should be based on solid materials with big entropy-driven conversion when submitted to an external stimulus change. We report the refrigerant capacity (RC = 2950 J kg−1, upon pressure change of ΔP = 1 kbar) in one of the most known and investigated spin-crossover material [Fe(phen) 2 (NCS) 2 ]. Our indirect obtained experimental data for the isothermal entropy change (ΔS T = 78 Jkg−1K−1) and the adiabatic temperature change (ΔT ad = 11 K) for ΔP = 1 kbar, agree with our theoretical calculations. From comparison between the thermodynamic and microscopic entropy descriptions, the origin of the barocaloric effect was ascribed to the pressure phonons activation in spin-crossover materials. Besides, a proper refrigeration thermodynamic cycle (Ericsson cycle) was quantitatively used for showing the refrigeration capacity of [Fe(phen) 2 (NCS) 2 ]. [ABSTRACT FROM AUTHOR]

Abstract: In this work we present a model to describe the magnetocaloric effect (MCE) in ferrimagnetic arrangements. Our model takes into account the magnetoelastic interactions in the two coupled magnetic sublattices, which can lead to the onset of the first order magnetic phase transition and the giant-MCE. Several profiles of the MCE, such as: the inverse- and giant-MCE were systematically studied. Application of the model to the ferromagnetic compounds GdAl2, Gd5(Ge1.72Si2.28), Gd5(Ge2Si2), and to the ferrimagnetic compound Y3Fe5O12 was performed, showing a good agreement with the experimental data. [Copyright &y& Elsevier]

We report a theoretical model formed by two coupled magnetic sublattices of localized spins in the presence of an applied magnetic field to investigate the magnetic characteristics and magnetocaloric properties of amorphous yttrium iron garnet. The magnetic state equation is based on Handrich–Kobe´s theory, where the amorphization is taken into account by introducing fluctuations in the exchange parameters. Experimental results report that Y 3 Fe 5 O 12 presents a structural phase transition from crystalline to amorphous caused by a variation of external pressure. This phase transition on Y 3 Fe 5 O 12 leads to interesting results in the magnetic properties and magnetocaloric quantities. [ABSTRACT FROM AUTHOR]

Abstract: The magnetocaloric effect (MCE) in the DyNi2, DyAl2 and Tb1− n Gd n Al2 (n=0, 0.4, 0.6) was theoretically investigated in this work. The DyNi2 and DyAl2 compounds are described considering a model Hamiltonian which includes the crystalline electrical field anisotropy. The anisotropic MCE was calculated changing the magnetic field direction from 〈111〉 to 〈001〉 in DyNi2 and from 〈100〉 to 〈011〉 in DyAl2. The influence of the second- and first-order spin-reorientation phase transitions on the MCE that occurs in these systems is discussed. For the calculations of the MCE thermodynamic quantities in the Tb1− n Gd n Al2 systems we take into account a two sites magnetic model, and good agreement with the available experimental data was obtained. [Copyright &y& Elsevier]

In this work we discuss the non-collinear ground-state reported for GdGa on the basis of a model Hamiltonian considering anisotropic exchange interactions. We show that a competition between intra and inter-sublattice exchange interactions can lead to a canted structure, which competes with a collinear (ferro or antiferromagnetic) order. The mean-field thermodynamic analysis of the model for S = 7 / 2 shows a good agreement between calculated and reported experimental data of the canting angle and isothermal entropy change for GdGa. • The spin reorientation mechanism in GdGa is described using a two-sublattices anisotropic Heisenberg Hamiltonian. • The semi-empirical exchange parameters are obtained after an analysis of the magnetization around the phase transitions. • The calculated canting angles and isothermal entropy change are in good agreement with available experimental data. [ABSTRACT FROM AUTHOR]