Abstract
The applicability of magnetocaloric materials is limited by irreversibility. In this work, we evaluate the reversible magnetocaloric response associated with magnetoelastic transitions in the framework of the Bean-Rodbell model. This model allows the description of both second- and first-order magnetoelastic transitions by the modification of the η parameter (η<1 for second-order and η>1 for first-order ones). The response is quantified via the Temperature-averaged Entropy Change (TEC), which has been shown to be an easy and effective figure of merit for magnetocaloric materials. A strong magnetic field dependence of TEC is found for first-order transitions, having a significant increase when the magnetic field is large enough to overcome the thermal hysteresis of the material observed at zero field. This field value, as well as the magnetic field evolution of the transition temperature, strongly depend on the atomic magnetic moment of the material. For a moderate magnetic field change of 2 T, first-order transitions with η≈1.3−1.8 have better TEC than those corresponding to stronger first-order transitions and even second-order ones.
Highlights
Magnetocaloric (MC) materials deserve the attention of the research community due to their possible application in solid-state refrigeration at room temperature [1,2,3].Prototypes of this technology have been shown to be energy efficient and environmentally friendly, aspects that are highly desired from the point of view of sustainability [4,5].The MC effect [6] is defined as the temperature change produced by the application/removal of a magnetic field in adiabatic conditions,∆Tad
We show that the reversible Temperature-averaged Entropy Change (TEC) has a strong magnetic field dependence for FOPT, exhibiting a significant increase when the magnetic field is large enough to overcome the thermal hysteresis of the material observed at zero field
To illustrate the hysteretic behavior in terms of the Bean-Rodbell model, Figure 1 shows, as an example, the temperature dependence of M and ∆Siso for an atomic magnetic moment of 7μ B for two values of the η parameter, which correspond to SOPT (η = 0.5) and FOPT cases (η = 1.5)
Summary
Magnetocaloric (MC) materials deserve the attention of the research community due to their possible application in solid-state refrigeration at room temperature [1,2,3].Prototypes of this technology have been shown to be energy efficient and environmentally friendly, aspects that are highly desired from the point of view of sustainability [4,5].The MC effect [6] is defined as the temperature change (or entropy change) produced by the application/removal of a magnetic field in adiabatic (or isothermal) conditions,∆Tad (or ∆Siso ). Magnetocaloric (MC) materials deserve the attention of the research community due to their possible application in solid-state refrigeration at room temperature [1,2,3]. Prototypes of this technology have been shown to be energy efficient and environmentally friendly, aspects that are highly desired from the point of view of sustainability [4,5]. SOPT materials present a moderate response in a wide temperature range, while FOPT materials present higher effects but in a narrow temperature span [9]. The analysis of the reversible response is crucial to evaluate the actual MC performance of a material
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